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68e3056785
linux-next/kernel/locking/lockdep.c
Boqun Feng 68e3056785 lockdep: Adjust check_redundant() for recursive read change 
check_redundant() will report redundancy if it finds a path could
replace the about-to-add dependency in the BFS search. With recursive
read lock changes, we certainly need to change the match function for
the check_redundant(), because the path needs to match not only the lock
class but also the dependency kinds. For example, if the about-to-add
dependency @prev -> @next is A -(SN)-> B, and we find a path A -(S*)->
.. -(*R)->B in the dependency graph with __bfs() (for simplicity, we can
also say we find an -(SR)-> path from A to B), we can not replace the
dependency with that path in the BFS search. Because the -(SN)->
dependency can make a strong path with a following -(S*)-> dependency,
however an -(SR)-> path cannot.

Further, we can replace an -(SN)-> dependency with a -(EN)-> path, that
means if we find a path which is stronger than or equal to the
about-to-add dependency, we can report the redundancy. By "stronger", it
means both the start and the end of the path are not weaker than the
start and the end of the dependency (E is "stronger" than S and N is
"stronger" than R), so that we can replace the dependency with that
path.

To make sure we find a path whose start point is not weaker than the
about-to-add dependency, we use a trick: the ->only_xr of the root
(start point) of __bfs() is initialized as @prev-> == 0, therefore if
@prev is E, __bfs() will pick only -(E*)-> for the first dependency,
otherwise, __bfs() can pick -(E*)-> or -(S*)-> for the first dependency.

To make sure we find a path whose end point is not weaker than the
about-to-add dependency, we replace the match function for __bfs()
check_redundant(), we check for the case that either @next is R
(anything is not weaker than it) or the end point of the path is N
(which is not weaker than anything).

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-11-boqun.feng@gmail.com
2020-08-26 12:42:05 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* kernel/lockdep.c
*
* Runtime locking correctness validator
*
* Started by Ingo Molnar:
*
* Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
*
* this code maps all the lock dependencies as they occur in a live kernel
* and will warn about the following classes of locking bugs:
*
* - lock inversion scenarios
* - circular lock dependencies
* - hardirq/softirq safe/unsafe locking bugs
*
* Bugs are reported even if the current locking scenario does not cause
* any deadlock at this point.
*
* I.e. if anytime in the past two locks were taken in a different order,
* even if it happened for another task, even if those were different
* locks (but of the same class as this lock), this code will detect it.
*
* Thanks to Arjan van de Ven for coming up with the initial idea of
* mapping lock dependencies runtime.
*/
#define DISABLE_BRANCH_PROFILING
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/sched/task.h>
#include <linux/sched/mm.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/stacktrace.h>
#include <linux/debug_locks.h>
#include <linux/irqflags.h>
#include <linux/utsname.h>
#include <linux/hash.h>
#include <linux/ftrace.h>
#include <linux/stringify.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/gfp.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/nmi.h>
#include <linux/rcupdate.h>
#include <linux/kprobes.h>
#include <asm/sections.h>
#include "lockdep_internals.h"
#define CREATE_TRACE_POINTS
#include <trace/events/lock.h>
#ifdef CONFIG_PROVE_LOCKING
int prove_locking = 1;
module_param(prove_locking, int, 0644);
#else
#define prove_locking 0
#endif
#ifdef CONFIG_LOCK_STAT
int lock_stat = 1;
module_param(lock_stat, int, 0644);
#else
#define lock_stat 0
#endif
/*
* lockdep_lock: protects the lockdep graph, the hashes and the
* class/list/hash allocators.
*
* This is one of the rare exceptions where it's justified
* to use a raw spinlock - we really dont want the spinlock
* code to recurse back into the lockdep code...
*/
static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static struct task_struct *__owner;
static inline void lockdep_lock(void)
{
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
arch_spin_lock(&__lock);
__owner = current;
current->lockdep_recursion++;
}
static inline void lockdep_unlock(void)
{
if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
return;
current->lockdep_recursion--;
__owner = NULL;
arch_spin_unlock(&__lock);
}
static inline bool lockdep_assert_locked(void)
{
return DEBUG_LOCKS_WARN_ON(__owner != current);
}
static struct task_struct *lockdep_selftest_task_struct;
static int graph_lock(void)
{
lockdep_lock();
/*
* Make sure that if another CPU detected a bug while
* walking the graph we dont change it (while the other
* CPU is busy printing out stuff with the graph lock
* dropped already)
*/
if (!debug_locks) {
lockdep_unlock();
return 0;
}
return 1;
}
static inline void graph_unlock(void)
{
lockdep_unlock();
}
/*
* Turn lock debugging off and return with 0 if it was off already,
* and also release the graph lock:
*/
static inline int debug_locks_off_graph_unlock(void)
{
int ret = debug_locks_off();
lockdep_unlock();
return ret;
}
unsigned long nr_list_entries;
static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
/*
* All data structures here are protected by the global debug_lock.
*
* nr_lock_classes is the number of elements of lock_classes[] that is
* in use.
*/
#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
#define KEYHASH_SIZE (1UL << KEYHASH_BITS)
static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
unsigned long nr_lock_classes;
unsigned long nr_zapped_classes;
#ifndef CONFIG_DEBUG_LOCKDEP
static
#endif
struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
static inline struct lock_class *hlock_class(struct held_lock *hlock)
{
unsigned int class_idx = hlock->class_idx;
/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
barrier();
if (!test_bit(class_idx, lock_classes_in_use)) {
/*
* Someone passed in garbage, we give up.
*/
DEBUG_LOCKS_WARN_ON(1);
return NULL;
}
/*
* At this point, if the passed hlock->class_idx is still garbage,
* we just have to live with it
*/
return lock_classes + class_idx;
}
#ifdef CONFIG_LOCK_STAT
static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
static inline u64 lockstat_clock(void)
{
return local_clock();
}
static int lock_point(unsigned long points[], unsigned long ip)
{
int i;
for (i = 0; i < LOCKSTAT_POINTS; i++) {
if (points[i] == 0) {
points[i] = ip;
break;
}
if (points[i] == ip)
break;
}
return i;
}
static void lock_time_inc(struct lock_time *lt, u64 time)
{
if (time > lt->max)
lt->max = time;
if (time < lt->min || !lt->nr)
lt->min = time;
lt->total += time;
lt->nr++;
}
static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
{
if (!src->nr)
return;
if (src->max > dst->max)
dst->max = src->max;
if (src->min < dst->min || !dst->nr)
dst->min = src->min;
dst->total += src->total;
dst->nr += src->nr;
}
struct lock_class_stats lock_stats(struct lock_class *class)
{
struct lock_class_stats stats;
int cpu, i;
memset(&stats, 0, sizeof(struct lock_class_stats));
for_each_possible_cpu(cpu) {
struct lock_class_stats *pcs =
&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
stats.contention_point[i] += pcs->contention_point[i];
for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
stats.contending_point[i] += pcs->contending_point[i];
lock_time_add(&pcs->read_waittime, &stats.read_waittime);
lock_time_add(&pcs->write_waittime, &stats.write_waittime);
lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
stats.bounces[i] += pcs->bounces[i];
}
return stats;
}
void clear_lock_stats(struct lock_class *class)
{
int cpu;
for_each_possible_cpu(cpu) {
struct lock_class_stats *cpu_stats =
&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
memset(cpu_stats, 0, sizeof(struct lock_class_stats));
}
memset(class->contention_point, 0, sizeof(class->contention_point));
memset(class->contending_point, 0, sizeof(class->contending_point));
}
static struct lock_class_stats *get_lock_stats(struct lock_class *class)
{
return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
}
static void lock_release_holdtime(struct held_lock *hlock)
{
struct lock_class_stats *stats;
u64 holdtime;
if (!lock_stat)
return;
holdtime = lockstat_clock() - hlock->holdtime_stamp;
stats = get_lock_stats(hlock_class(hlock));
if (hlock->read)
lock_time_inc(&stats->read_holdtime, holdtime);
else
lock_time_inc(&stats->write_holdtime, holdtime);
}
#else
static inline void lock_release_holdtime(struct held_lock *hlock)
{
}
#endif
/*
* We keep a global list of all lock classes. The list is only accessed with
* the lockdep spinlock lock held. free_lock_classes is a list with free
* elements. These elements are linked together by the lock_entry member in
* struct lock_class.
*/
LIST_HEAD(all_lock_classes);
static LIST_HEAD(free_lock_classes);
/**
* struct pending_free - information about data structures about to be freed
* @zapped: Head of a list with struct lock_class elements.
* @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
* are about to be freed.
*/
struct pending_free {
struct list_head zapped;
DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
};
/**
* struct delayed_free - data structures used for delayed freeing
*
* A data structure for delayed freeing of data structures that may be
* accessed by RCU readers at the time these were freed.
*
* @rcu_head: Used to schedule an RCU callback for freeing data structures.
* @index: Index of @pf to which freed data structures are added.
* @scheduled: Whether or not an RCU callback has been scheduled.
* @pf: Array with information about data structures about to be freed.
*/
static struct delayed_free {
struct rcu_head rcu_head;
int index;
int scheduled;
struct pending_free pf[2];
} delayed_free;
/*
* The lockdep classes are in a hash-table as well, for fast lookup:
*/
#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
#define classhashentry(key) (classhash_table + __classhashfn((key)))
static struct hlist_head classhash_table[CLASSHASH_SIZE];
/*
* We put the lock dependency chains into a hash-table as well, to cache
* their existence:
*/
#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
static struct hlist_head chainhash_table[CHAINHASH_SIZE];
/*
* The hash key of the lock dependency chains is a hash itself too:
* it's a hash of all locks taken up to that lock, including that lock.
* It's a 64-bit hash, because it's important for the keys to be
* unique.
*/
static inline u64 iterate_chain_key(u64 key, u32 idx)
{
u32 k0 = key, k1 = key >> 32;
__jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
return k0 | (u64)k1 << 32;
}
void lockdep_init_task(struct task_struct *task)
{
task->lockdep_depth = 0; /* no locks held yet */
task->curr_chain_key = INITIAL_CHAIN_KEY;
task->lockdep_recursion = 0;
}
static __always_inline void lockdep_recursion_finish(void)
{
if (WARN_ON_ONCE((--current->lockdep_recursion) & LOCKDEP_RECURSION_MASK))
current->lockdep_recursion = 0;
}
void lockdep_set_selftest_task(struct task_struct *task)
{
lockdep_selftest_task_struct = task;
}
/*
* Debugging switches:
*/
#define VERBOSE 0
#define VERY_VERBOSE 0
#if VERBOSE
# define HARDIRQ_VERBOSE 1
# define SOFTIRQ_VERBOSE 1
#else
# define HARDIRQ_VERBOSE 0
# define SOFTIRQ_VERBOSE 0
#endif
#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
/*
* Quick filtering for interesting events:
*/
static int class_filter(struct lock_class *class)
{
#if 0
/* Example */
if (class->name_version == 1 &&
!strcmp(class->name, "lockname"))
return 1;
if (class->name_version == 1 &&
!strcmp(class->name, "&struct->lockfield"))
return 1;
#endif
/* Filter everything else. 1 would be to allow everything else */
return 0;
}
#endif
static int verbose(struct lock_class *class)
{
#if VERBOSE
return class_filter(class);
#endif
return 0;
}
static void print_lockdep_off(const char *bug_msg)
{
printk(KERN_DEBUG "%s\n", bug_msg);
printk(KERN_DEBUG "turning off the locking correctness validator.\n");
#ifdef CONFIG_LOCK_STAT
printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
#endif
}
unsigned long nr_stack_trace_entries;
#ifdef CONFIG_PROVE_LOCKING
/**
* struct lock_trace - single stack backtrace
* @hash_entry: Entry in a stack_trace_hash[] list.
* @hash: jhash() of @entries.
* @nr_entries: Number of entries in @entries.
* @entries: Actual stack backtrace.
*/
struct lock_trace {
struct hlist_node hash_entry;
u32 hash;
u32 nr_entries;
unsigned long entries[] __aligned(sizeof(unsigned long));
};
#define LOCK_TRACE_SIZE_IN_LONGS \
(sizeof(struct lock_trace) / sizeof(unsigned long))
/*
* Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
*/
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
{
return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
memcmp(t1->entries, t2->entries,
t1->nr_entries * sizeof(t1->entries[0])) == 0;
}
static struct lock_trace *save_trace(void)
{
struct lock_trace *trace, *t2;
struct hlist_head *hash_head;
u32 hash;
int max_entries;
BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
LOCK_TRACE_SIZE_IN_LONGS;
if (max_entries <= 0) {
if (!debug_locks_off_graph_unlock())
return NULL;
print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
dump_stack();
return NULL;
}
trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
hash = jhash(trace->entries, trace->nr_entries *
sizeof(trace->entries[0]), 0);
trace->hash = hash;
hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
hlist_for_each_entry(t2, hash_head, hash_entry) {
if (traces_identical(trace, t2))
return t2;
}
nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
hlist_add_head(&trace->hash_entry, hash_head);
return trace;
}
/* Return the number of stack traces in the stack_trace[] array. */
u64 lockdep_stack_trace_count(void)
{
struct lock_trace *trace;
u64 c = 0;
int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
c++;
}
}
return c;
}
/* Return the number of stack hash chains that have at least one stack trace. */
u64 lockdep_stack_hash_count(void)
{
u64 c = 0;
int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
if (!hlist_empty(&stack_trace_hash[i]))
c++;
return c;
}
#endif
unsigned int nr_hardirq_chains;
unsigned int nr_softirq_chains;
unsigned int nr_process_chains;
unsigned int max_lockdep_depth;
#ifdef CONFIG_DEBUG_LOCKDEP
/*
* Various lockdep statistics:
*/
DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
#endif
#ifdef CONFIG_PROVE_LOCKING
/*
* Locking printouts:
*/
#define __USAGE(__STATE) \
[LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
[LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
[LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
[LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
static const char *usage_str[] =
{
#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
[LOCK_USED] = "INITIAL USE",
[LOCK_USAGE_STATES] = "IN-NMI",
};
#endif
const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
{
return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
}
static inline unsigned long lock_flag(enum lock_usage_bit bit)
{
return 1UL << bit;
}
static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
{
/*
* The usage character defaults to '.' (i.e., irqs disabled and not in
* irq context), which is the safest usage category.
*/
char c = '.';
/*
* The order of the following usage checks matters, which will
* result in the outcome character as follows:
*
* - '+': irq is enabled and not in irq context
* - '-': in irq context and irq is disabled
* - '?': in irq context and irq is enabled
*/
if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
c = '+';
if (class->usage_mask & lock_flag(bit))
c = '?';
} else if (class->usage_mask & lock_flag(bit))
c = '-';
return c;
}
void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
{
int i = 0;
#define LOCKDEP_STATE(__STATE) \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
#include "lockdep_states.h"
#undef LOCKDEP_STATE
usage[i] = '\0';
}
static void __print_lock_name(struct lock_class *class)
{
char str[KSYM_NAME_LEN];
const char *name;
name = class->name;
if (!name) {
name = __get_key_name(class->key, str);
printk(KERN_CONT "%s", name);
} else {
printk(KERN_CONT "%s", name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
if (class->subclass)
printk(KERN_CONT "/%d", class->subclass);
}
}
static void print_lock_name(struct lock_class *class)
{
char usage[LOCK_USAGE_CHARS];
get_usage_chars(class, usage);
printk(KERN_CONT " (");
__print_lock_name(class);
printk(KERN_CONT "){%s}-{%hd:%hd}", usage,
class->wait_type_outer ?: class->wait_type_inner,
class->wait_type_inner);
}
static void print_lockdep_cache(struct lockdep_map *lock)
{
const char *name;
char str[KSYM_NAME_LEN];
name = lock->name;
if (!name)
name = __get_key_name(lock->key->subkeys, str);
printk(KERN_CONT "%s", name);
}
static void print_lock(struct held_lock *hlock)
{
/*
* We can be called locklessly through debug_show_all_locks() so be
* extra careful, the hlock might have been released and cleared.
*
* If this indeed happens, lets pretend it does not hurt to continue
* to print the lock unless the hlock class_idx does not point to a
* registered class. The rationale here is: since we don't attempt
* to distinguish whether we are in this situation, if it just
* happened we can't count on class_idx to tell either.
*/
struct lock_class *lock = hlock_class(hlock);
if (!lock) {
printk(KERN_CONT "<RELEASED>\n");
return;
}
printk(KERN_CONT "%px", hlock->instance);
print_lock_name(lock);
printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
}
static void lockdep_print_held_locks(struct task_struct *p)
{
int i, depth = READ_ONCE(p->lockdep_depth);
if (!depth)
printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
else
printk("%d lock%s held by %s/%d:\n", depth,
depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
/*
* It's not reliable to print a task's held locks if it's not sleeping
* and it's not the current task.
*/
if (p->state == TASK_RUNNING && p != current)
return;
for (i = 0; i < depth; i++) {
printk(" #%d: ", i);
print_lock(p->held_locks + i);
}
}
static void print_kernel_ident(void)
{
printk("%s %.*s %s\n", init_utsname()->release,
(int)strcspn(init_utsname()->version, " "),
init_utsname()->version,
print_tainted());
}
static int very_verbose(struct lock_class *class)
{
#if VERY_VERBOSE
return class_filter(class);
#endif
return 0;
}
/*
* Is this the address of a static object:
*/
#ifdef __KERNEL__
static int static_obj(const void *obj)
{
unsigned long start = (unsigned long) &_stext,
end = (unsigned long) &_end,
addr = (unsigned long) obj;
if (arch_is_kernel_initmem_freed(addr))
return 0;
/*
* static variable?
*/
if ((addr >= start) && (addr < end))
return 1;
if (arch_is_kernel_data(addr))
return 1;
/*
* in-kernel percpu var?
*/
if (is_kernel_percpu_address(addr))
return 1;
/*
* module static or percpu var?
*/
return is_module_address(addr) || is_module_percpu_address(addr);
}
#endif
/*
* To make lock name printouts unique, we calculate a unique
* class->name_version generation counter. The caller must hold the graph
* lock.
*/
static int count_matching_names(struct lock_class *new_class)
{
struct lock_class *class;
int count = 0;
if (!new_class->name)
return 0;
list_for_each_entry(class, &all_lock_classes, lock_entry) {
if (new_class->key - new_class->subclass == class->key)
return class->name_version;
if (class->name && !strcmp(class->name, new_class->name))
count = max(count, class->name_version);
}
return count + 1;
}
/* used from NMI context -- must be lockless */
static __always_inline struct lock_class *
look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
{
struct lockdep_subclass_key *key;
struct hlist_head *hash_head;
struct lock_class *class;
if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
debug_locks_off();
printk(KERN_ERR
"BUG: looking up invalid subclass: %u\n", subclass);
printk(KERN_ERR
"turning off the locking correctness validator.\n");
dump_stack();
return NULL;
}
/*
* If it is not initialised then it has never been locked,
* so it won't be present in the hash table.
*/
if (unlikely(!lock->key))
return NULL;
/*
* NOTE: the class-key must be unique. For dynamic locks, a static
* lock_class_key variable is passed in through the mutex_init()
* (or spin_lock_init()) call - which acts as the key. For static
* locks we use the lock object itself as the key.
*/
BUILD_BUG_ON(sizeof(struct lock_class_key) >
sizeof(struct lockdep_map));
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
/*
* We do an RCU walk of the hash, see lockdep_free_key_range().
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return NULL;
hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
if (class->key == key) {
/*
* Huh! same key, different name? Did someone trample
* on some memory? We're most confused.
*/
WARN_ON_ONCE(class->name != lock->name &&
lock->key != &__lockdep_no_validate__);
return class;
}
}
return NULL;
}
/*
* Static locks do not have their class-keys yet - for them the key is
* the lock object itself. If the lock is in the per cpu area, the
* canonical address of the lock (per cpu offset removed) is used.
*/
static bool assign_lock_key(struct lockdep_map *lock)
{
unsigned long can_addr, addr = (unsigned long)lock;
#ifdef __KERNEL__
/*
* lockdep_free_key_range() assumes that struct lock_class_key
* objects do not overlap. Since we use the address of lock
* objects as class key for static objects, check whether the
* size of lock_class_key objects does not exceed the size of
* the smallest lock object.
*/
BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
#endif
if (__is_kernel_percpu_address(addr, &can_addr))
lock->key = (void *)can_addr;
else if (__is_module_percpu_address(addr, &can_addr))
lock->key = (void *)can_addr;
else if (static_obj(lock))
lock->key = (void *)lock;
else {
/* Debug-check: all keys must be persistent! */
debug_locks_off();
pr_err("INFO: trying to register non-static key.\n");
pr_err("the code is fine but needs lockdep annotation.\n");
pr_err("turning off the locking correctness validator.\n");
dump_stack();
return false;
}
return true;
}
#ifdef CONFIG_DEBUG_LOCKDEP
/* Check whether element @e occurs in list @h */
static bool in_list(struct list_head *e, struct list_head *h)
{
struct list_head *f;
list_for_each(f, h) {
if (e == f)
return true;
}
return false;
}
/*
* Check whether entry @e occurs in any of the locks_after or locks_before
* lists.
*/
static bool in_any_class_list(struct list_head *e)
{
struct lock_class *class;
int i;
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (in_list(e, &class->locks_after) ||
in_list(e, &class->locks_before))
return true;
}
return false;
}
static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
{
struct lock_list *e;
list_for_each_entry(e, h, entry) {
if (e->links_to != c) {
printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
c->name ? : "(?)",
(unsigned long)(e - list_entries),
e->links_to && e->links_to->name ?
e->links_to->name : "(?)",
e->class && e->class->name ? e->class->name :
"(?)");
return false;
}
}
return true;
}
#ifdef CONFIG_PROVE_LOCKING
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
#endif
static bool check_lock_chain_key(struct lock_chain *chain)
{
#ifdef CONFIG_PROVE_LOCKING
u64 chain_key = INITIAL_CHAIN_KEY;
int i;
for (i = chain->base; i < chain->base + chain->depth; i++)
chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
/*
* The 'unsigned long long' casts avoid that a compiler warning
* is reported when building tools/lib/lockdep.
*/
if (chain->chain_key != chain_key) {
printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
(unsigned long long)(chain - lock_chains),
(unsigned long long)chain->chain_key,
(unsigned long long)chain_key);
return false;
}
#endif
return true;
}
static bool in_any_zapped_class_list(struct lock_class *class)
{
struct pending_free *pf;
int i;
for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
if (in_list(&class->lock_entry, &pf->zapped))
return true;
}
return false;
}
static bool __check_data_structures(void)
{
struct lock_class *class;
struct lock_chain *chain;
struct hlist_head *head;
struct lock_list *e;
int i;
/* Check whether all classes occur in a lock list. */
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (!in_list(&class->lock_entry, &all_lock_classes) &&
!in_list(&class->lock_entry, &free_lock_classes) &&
!in_any_zapped_class_list(class)) {
printk(KERN_INFO "class %px/%s is not in any class list\n",
class, class->name ? : "(?)");
return false;
}
}
/* Check whether all classes have valid lock lists. */
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
class = &lock_classes[i];
if (!class_lock_list_valid(class, &class->locks_before))
return false;
if (!class_lock_list_valid(class, &class->locks_after))
return false;
}
/* Check the chain_key of all lock chains. */
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
head = chainhash_table + i;
hlist_for_each_entry_rcu(chain, head, entry) {
if (!check_lock_chain_key(chain))
return false;
}
}
/*
* Check whether all list entries that are in use occur in a class
* lock list.
*/
for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
e = list_entries + i;
if (!in_any_class_list(&e->entry)) {
printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
(unsigned int)(e - list_entries),
e->class->name ? : "(?)",
e->links_to->name ? : "(?)");
return false;
}
}
/*
* Check whether all list entries that are not in use do not occur in
* a class lock list.
*/
for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
e = list_entries + i;
if (in_any_class_list(&e->entry)) {
printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
(unsigned int)(e - list_entries),
e->class && e->class->name ? e->class->name :
"(?)",
e->links_to && e->links_to->name ?
e->links_to->name : "(?)");
return false;
}
}
return true;
}
int check_consistency = 0;
module_param(check_consistency, int, 0644);
static void check_data_structures(void)
{
static bool once = false;
if (check_consistency && !once) {
if (!__check_data_structures()) {
once = true;
WARN_ON(once);
}
}
}
#else /* CONFIG_DEBUG_LOCKDEP */
static inline void check_data_structures(void) { }
#endif /* CONFIG_DEBUG_LOCKDEP */
static void init_chain_block_buckets(void);
/*
* Initialize the lock_classes[] array elements, the free_lock_classes list
* and also the delayed_free structure.
*/
static void init_data_structures_once(void)
{
static bool __read_mostly ds_initialized, rcu_head_initialized;
int i;
if (likely(rcu_head_initialized))
return;
if (system_state >= SYSTEM_SCHEDULING) {
init_rcu_head(&delayed_free.rcu_head);
rcu_head_initialized = true;
}
if (ds_initialized)
return;
ds_initialized = true;
INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
INIT_LIST_HEAD(&lock_classes[i].locks_after);
INIT_LIST_HEAD(&lock_classes[i].locks_before);
}
init_chain_block_buckets();
}
static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
{
unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
return lock_keys_hash + hash;
}
/* Register a dynamically allocated key. */
void lockdep_register_key(struct lock_class_key *key)
{
struct hlist_head *hash_head;
struct lock_class_key *k;
unsigned long flags;
if (WARN_ON_ONCE(static_obj(key)))
return;
hash_head = keyhashentry(key);
raw_local_irq_save(flags);
if (!graph_lock())
goto restore_irqs;
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (WARN_ON_ONCE(k == key))
goto out_unlock;
}
hlist_add_head_rcu(&key->hash_entry, hash_head);
out_unlock:
graph_unlock();
restore_irqs:
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lockdep_register_key);
/* Check whether a key has been registered as a dynamic key. */
static bool is_dynamic_key(const struct lock_class_key *key)
{
struct hlist_head *hash_head;
struct lock_class_key *k;
bool found = false;
if (WARN_ON_ONCE(static_obj(key)))
return false;
/*
* If lock debugging is disabled lock_keys_hash[] may contain
* pointers to memory that has already been freed. Avoid triggering
* a use-after-free in that case by returning early.
*/
if (!debug_locks)
return true;
hash_head = keyhashentry(key);
rcu_read_lock();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (k == key) {
found = true;
break;
}
}
rcu_read_unlock();
return found;
}
/*
* Register a lock's class in the hash-table, if the class is not present
* yet. Otherwise we look it up. We cache the result in the lock object
* itself, so actual lookup of the hash should be once per lock object.
*/
static struct lock_class *
register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
{
struct lockdep_subclass_key *key;
struct hlist_head *hash_head;
struct lock_class *class;
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
class = look_up_lock_class(lock, subclass);
if (likely(class))
goto out_set_class_cache;
if (!lock->key) {
if (!assign_lock_key(lock))
return NULL;
} else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
return NULL;
}
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
if (!graph_lock()) {
return NULL;
}
/*
* We have to do the hash-walk again, to avoid races
* with another CPU:
*/
hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
if (class->key == key)
goto out_unlock_set;
}
init_data_structures_once();
/* Allocate a new lock class and add it to the hash. */
class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
lock_entry);
if (!class) {
if (!debug_locks_off_graph_unlock()) {
return NULL;
}
print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
dump_stack();
return NULL;
}
nr_lock_classes++;
__set_bit(class - lock_classes, lock_classes_in_use);
debug_atomic_inc(nr_unused_locks);
class->key = key;
class->name = lock->name;
class->subclass = subclass;
WARN_ON_ONCE(!list_empty(&class->locks_before));
WARN_ON_ONCE(!list_empty(&class->locks_after));
class->name_version = count_matching_names(class);
class->wait_type_inner = lock->wait_type_inner;
class->wait_type_outer = lock->wait_type_outer;
/*
* We use RCU's safe list-add method to make
* parallel walking of the hash-list safe:
*/
hlist_add_head_rcu(&class->hash_entry, hash_head);
/*
* Remove the class from the free list and add it to the global list
* of classes.
*/
list_move_tail(&class->lock_entry, &all_lock_classes);
if (verbose(class)) {
graph_unlock();
printk("\nnew class %px: %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
if (!graph_lock()) {
return NULL;
}
}
out_unlock_set:
graph_unlock();
out_set_class_cache:
if (!subclass || force)
lock->class_cache[0] = class;
else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
lock->class_cache[subclass] = class;
/*
* Hash collision, did we smoke some? We found a class with a matching
* hash but the subclass -- which is hashed in -- didn't match.
*/
if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
return NULL;
return class;
}
#ifdef CONFIG_PROVE_LOCKING
/*
* Allocate a lockdep entry. (assumes the graph_lock held, returns
* with NULL on failure)
*/
static struct lock_list *alloc_list_entry(void)
{
int idx = find_first_zero_bit(list_entries_in_use,
ARRAY_SIZE(list_entries));
if (idx >= ARRAY_SIZE(list_entries)) {
if (!debug_locks_off_graph_unlock())
return NULL;
print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
dump_stack();
return NULL;
}
nr_list_entries++;
__set_bit(idx, list_entries_in_use);
return list_entries + idx;
}
/*
* Add a new dependency to the head of the list:
*/
static int add_lock_to_list(struct lock_class *this,
struct lock_class *links_to, struct list_head *head,
unsigned long ip, u16 distance, u8 dep,
const struct lock_trace *trace)
{
struct lock_list *entry;
/*
* Lock not present yet - get a new dependency struct and
* add it to the list:
*/
entry = alloc_list_entry();
if (!entry)
return 0;
entry->class = this;
entry->links_to = links_to;
entry->dep = dep;
entry->distance = distance;
entry->trace = trace;
/*
* Both allocation and removal are done under the graph lock; but
* iteration is under RCU-sched; see look_up_lock_class() and
* lockdep_free_key_range().
*/
list_add_tail_rcu(&entry->entry, head);
return 1;
}
/*
* For good efficiency of modular, we use power of 2
*/
#define MAX_CIRCULAR_QUEUE_SIZE 4096UL
#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
/*
* The circular_queue and helpers are used to implement graph
* breadth-first search (BFS) algorithm, by which we can determine
* whether there is a path from a lock to another. In deadlock checks,
* a path from the next lock to be acquired to a previous held lock
* indicates that adding the <prev> -> <next> lock dependency will
* produce a circle in the graph. Breadth-first search instead of
* depth-first search is used in order to find the shortest (circular)
* path.
*/
struct circular_queue {
struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
unsigned int front, rear;
};
static struct circular_queue lock_cq;
unsigned int max_bfs_queue_depth;
static unsigned int lockdep_dependency_gen_id;
static inline void __cq_init(struct circular_queue *cq)
{
cq->front = cq->rear = 0;
lockdep_dependency_gen_id++;
}
static inline int __cq_empty(struct circular_queue *cq)
{
return (cq->front == cq->rear);
}
static inline int __cq_full(struct circular_queue *cq)
{
return ((cq->rear + 1) & CQ_MASK) == cq->front;
}
static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
{
if (__cq_full(cq))
return -1;
cq->element[cq->rear] = elem;
cq->rear = (cq->rear + 1) & CQ_MASK;
return 0;
}
/*
* Dequeue an element from the circular_queue, return a lock_list if
* the queue is not empty, or NULL if otherwise.
*/
static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
{
struct lock_list * lock;
if (__cq_empty(cq))
return NULL;
lock = cq->element[cq->front];
cq->front = (cq->front + 1) & CQ_MASK;
return lock;
}
static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
{
return (cq->rear - cq->front) & CQ_MASK;
}
static inline void mark_lock_accessed(struct lock_list *lock)
{
lock->class->dep_gen_id = lockdep_dependency_gen_id;
}
static inline void visit_lock_entry(struct lock_list *lock,
struct lock_list *parent)
{
lock->parent = parent;
}
static inline unsigned long lock_accessed(struct lock_list *lock)
{
return lock->class->dep_gen_id == lockdep_dependency_gen_id;
}
static inline struct lock_list *get_lock_parent(struct lock_list *child)
{
return child->parent;
}
static inline int get_lock_depth(struct lock_list *child)
{
int depth = 0;
struct lock_list *parent;
while ((parent = get_lock_parent(child))) {
child = parent;
depth++;
}
return depth;
}
/*
* Return the forward or backward dependency list.
*
* @lock: the lock_list to get its class's dependency list
* @offset: the offset to struct lock_class to determine whether it is
* locks_after or locks_before
*/
static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
{
void *lock_class = lock->class;
return lock_class + offset;
}
/*
* Return values of a bfs search:
*
* BFS_E* indicates an error
* BFS_R* indicates a result (match or not)
*
* BFS_EINVALIDNODE: Find a invalid node in the graph.
*
* BFS_EQUEUEFULL: The queue is full while doing the bfs.
*
* BFS_RMATCH: Find the matched node in the graph, and put that node into
* *@target_entry.
*
* BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
* _unchanged_.
*/
enum bfs_result {
BFS_EINVALIDNODE = -2,
BFS_EQUEUEFULL = -1,
BFS_RMATCH = 0,
BFS_RNOMATCH = 1,
};
/*
* bfs_result < 0 means error
*/
static inline bool bfs_error(enum bfs_result res)
{
return res < 0;
}
/*
* DEP_*_BIT in lock_list::dep
*
* For dependency @prev -> @next:
*
* SR: @prev is shared reader (->read != 0) and @next is recursive reader
* (->read == 2)
* ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
* SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
* EN: @prev is exclusive locker and @next is non-recursive locker
*
* Note that we define the value of DEP_*_BITs so that:
* bit0 is prev->read == 0
* bit1 is next->read != 2
*/
#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
#define DEP_SR_MASK (1U << (DEP_SR_BIT))
#define DEP_ER_MASK (1U << (DEP_ER_BIT))
#define DEP_SN_MASK (1U << (DEP_SN_BIT))
#define DEP_EN_MASK (1U << (DEP_EN_BIT))
static inline unsigned int
__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
{
return (prev->read == 0) + ((next->read != 2) << 1);
}
static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
{
return 1U << __calc_dep_bit(prev, next);
}
/*
* calculate the dep_bit for backwards edges. We care about whether @prev is
* shared and whether @next is recursive.
*/
static inline unsigned int
__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
{
return (next->read != 2) + ((prev->read == 0) << 1);
}
static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
{
return 1U << __calc_dep_bitb(prev, next);
}
/*
* Initialize a lock_list entry @lock belonging to @class as the root for a BFS
* search.
*/
static inline void __bfs_init_root(struct lock_list *lock,
struct lock_class *class)
{
lock->class = class;
lock->parent = NULL;
lock->only_xr = 0;
}
/*
* Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
* root for a BFS search.
*
* ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
* that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
* and -(S*)->.
*/
static inline void bfs_init_root(struct lock_list *lock,
struct held_lock *hlock)
{
__bfs_init_root(lock, hlock_class(hlock));
lock->only_xr = (hlock->read == 2);
}
/*
* Similar to bfs_init_root() but initialize the root for backwards BFS.
*
* ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
* that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
* -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
*/
static inline void bfs_init_rootb(struct lock_list *lock,
struct held_lock *hlock)
{
__bfs_init_root(lock, hlock_class(hlock));
lock->only_xr = (hlock->read != 0);
}
/*
* Breadth-First Search to find a strong path in the dependency graph.
*
* @source_entry: the source of the path we are searching for.
* @data: data used for the second parameter of @match function
* @match: match function for the search
* @target_entry: pointer to the target of a matched path
* @offset: the offset to struct lock_class to determine whether it is
* locks_after or locks_before
*
* We may have multiple edges (considering different kinds of dependencies,
* e.g. ER and SN) between two nodes in the dependency graph. But
* only the strong dependency path in the graph is relevant to deadlocks. A
* strong dependency path is a dependency path that doesn't have two adjacent
* dependencies as -(*R)-> -(S*)->, please see:
*
* Documentation/locking/lockdep-design.rst
*
* for more explanation of the definition of strong dependency paths
*
* In __bfs(), we only traverse in the strong dependency path:
*
* In lock_list::only_xr, we record whether the previous dependency only
* has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
* filter out any -(S*)-> in the current dependency and after that, the
* ->only_xr is set according to whether we only have -(*R)-> left.
*/
static enum bfs_result __bfs(struct lock_list *source_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry,
int offset)
{
struct lock_list *entry;
struct lock_list *lock;
struct list_head *head;
struct circular_queue *cq = &lock_cq;
enum bfs_result ret = BFS_RNOMATCH;
lockdep_assert_locked();
if (match(source_entry, data)) {
*target_entry = source_entry;
ret = BFS_RMATCH;
goto exit;
}
head = get_dep_list(source_entry, offset);
if (list_empty(head))
goto exit;
__cq_init(cq);
__cq_enqueue(cq, source_entry);
while ((lock = __cq_dequeue(cq))) {
bool prev_only_xr;
if (!lock->class) {
ret = BFS_EINVALIDNODE;
goto exit;
}
/*
* If we have visited all the dependencies from this @lock to
* others (iow, if we have visited all lock_list entries in
* @lock->class->locks_{after,before}) we skip, otherwise go
* and visit all the dependencies in the list and mark this
* list accessed.
*/
if (lock_accessed(lock))
continue;
else
mark_lock_accessed(lock);
head = get_dep_list(lock, offset);
prev_only_xr = lock->only_xr;
list_for_each_entry_rcu(entry, head, entry) {
unsigned int cq_depth;
u8 dep = entry->dep;
/*
* Mask out all -(S*)-> if we only have *R in previous
* step, because -(*R)-> -(S*)-> don't make up a strong
* dependency.
*/
if (prev_only_xr)
dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
/* If nothing left, we skip */
if (!dep)
continue;
/* If there are only -(*R)-> left, set that for the next step */
entry->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
visit_lock_entry(entry, lock);
if (match(entry, data)) {
*target_entry = entry;
ret = BFS_RMATCH;
goto exit;
}
if (__cq_enqueue(cq, entry)) {
ret = BFS_EQUEUEFULL;
goto exit;
}
cq_depth = __cq_get_elem_count(cq);
if (max_bfs_queue_depth < cq_depth)
max_bfs_queue_depth = cq_depth;
}
}
exit:
return ret;
}
static inline enum bfs_result
__bfs_forwards(struct lock_list *src_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
return __bfs(src_entry, data, match, target_entry,
offsetof(struct lock_class, locks_after));
}
static inline enum bfs_result
__bfs_backwards(struct lock_list *src_entry,
void *data,
bool (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
return __bfs(src_entry, data, match, target_entry,
offsetof(struct lock_class, locks_before));
}
static void print_lock_trace(const struct lock_trace *trace,
unsigned int spaces)
{
stack_trace_print(trace->entries, trace->nr_entries, spaces);
}
/*
* Print a dependency chain entry (this is only done when a deadlock
* has been detected):
*/
static noinline void
print_circular_bug_entry(struct lock_list *target, int depth)
{
if (debug_locks_silent)
return;
printk("\n-> #%u", depth);
print_lock_name(target->class);
printk(KERN_CONT ":\n");
print_lock_trace(target->trace, 6);
}
static void
print_circular_lock_scenario(struct held_lock *src,
struct held_lock *tgt,
struct lock_list *prt)
{
struct lock_class *source = hlock_class(src);
struct lock_class *target = hlock_class(tgt);
struct lock_class *parent = prt->class;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
if (parent != source) {
printk("Chain exists of:\n ");
__print_lock_name(source);
printk(KERN_CONT " --> ");
__print_lock_name(parent);
printk(KERN_CONT " --> ");
__print_lock_name(target);
printk(KERN_CONT "\n\n");
}
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
__print_lock_name(target);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(parent);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(target);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(source);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
/*
* When a circular dependency is detected, print the
* header first:
*/
static noinline void
print_circular_bug_header(struct lock_list *entry, unsigned int depth,
struct held_lock *check_src,
struct held_lock *check_tgt)
{
struct task_struct *curr = current;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("======================================================\n");
pr_warn("WARNING: possible circular locking dependency detected\n");
print_kernel_ident();
pr_warn("------------------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(check_src);
pr_warn("\nbut task is already holding lock:\n");
print_lock(check_tgt);
pr_warn("\nwhich lock already depends on the new lock.\n\n");
pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
print_circular_bug_entry(entry, depth);
}
/*
* We are about to add A -> B into the dependency graph, and in __bfs() a
* strong dependency path A -> .. -> B is found: hlock_class equals
* entry->class.
*
* If A -> .. -> B can replace A -> B in any __bfs() search (means the former
* is _stronger_ than or equal to the latter), we consider A -> B as redundant.
* For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
* -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
* dependency graph, as any strong path ..-> A -> B ->.. we can get with
* having dependency A -> B, we could already get a equivalent path ..-> A ->
* .. -> B -> .. with A -> .. -> B. Therefore A -> B is reduntant.
*
* We need to make sure both the start and the end of A -> .. -> B is not
* weaker than A -> B. For the start part, please see the comment in
* check_redundant(). For the end part, we need:
*
* Either
*
* a) A -> B is -(*R)-> (everything is not weaker than that)
*
* or
*
* b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
*
*/
static inline bool hlock_equal(struct lock_list *entry, void *data)
{
struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
(hlock->read == 2 || /* A -> B is -(*R)-> */
!entry->only_xr); /* A -> .. -> B is -(*N)-> */
}
/*
* We are about to add B -> A into the dependency graph, and in __bfs() a
* strong dependency path A -> .. -> B is found: hlock_class equals
* entry->class.
*
* We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
* dependency cycle, that means:
*
* Either
*
* a) B -> A is -(E*)->
*
* or
*
* b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
*
* as then we don't have -(*R)-> -(S*)-> in the cycle.
*/
static inline bool hlock_conflict(struct lock_list *entry, void *data)
{
struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
(hlock->read == 0 || /* B -> A is -(E*)-> */
!entry->only_xr); /* A -> .. -> B is -(*N)-> */
}
static noinline void print_circular_bug(struct lock_list *this,
struct lock_list *target,
struct held_lock *check_src,
struct held_lock *check_tgt)
{
struct task_struct *curr = current;
struct lock_list *parent;
struct lock_list *first_parent;
int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
this->trace = save_trace();
if (!this->trace)
return;
depth = get_lock_depth(target);
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target);
first_parent = parent;
while (parent) {
print_circular_bug_entry(parent, --depth);
parent = get_lock_parent(parent);
}
printk("\nother info that might help us debug this:\n\n");
print_circular_lock_scenario(check_src, check_tgt,
first_parent);
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
dump_stack();
}
static noinline void print_bfs_bug(int ret)
{
if (!debug_locks_off_graph_unlock())
return;
/*
* Breadth-first-search failed, graph got corrupted?
*/
WARN(1, "lockdep bfs error:%d\n", ret);
}
static bool noop_count(struct lock_list *entry, void *data)
{
(*(unsigned long *)data)++;
return false;
}
static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
{
unsigned long count = 0;
struct lock_list *target_entry;
__bfs_forwards(this, (void *)&count, noop_count, &target_entry);
return count;
}
unsigned long lockdep_count_forward_deps(struct lock_class *class)
{
unsigned long ret, flags;
struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
ret = __lockdep_count_forward_deps(&this);
lockdep_unlock();
raw_local_irq_restore(flags);
return ret;
}
static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
{
unsigned long count = 0;
struct lock_list *target_entry;
__bfs_backwards(this, (void *)&count, noop_count, &target_entry);
return count;
}
unsigned long lockdep_count_backward_deps(struct lock_class *class)
{
unsigned long ret, flags;
struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
ret = __lockdep_count_backward_deps(&this);
lockdep_unlock();
raw_local_irq_restore(flags);
return ret;
}
/*
* Check that the dependency graph starting at <src> can lead to
* <target> or not.
*/
static noinline enum bfs_result
check_path(struct held_lock *target, struct lock_list *src_entry,
bool (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
{
enum bfs_result ret;
ret = __bfs_forwards(src_entry, target, match, target_entry);
if (unlikely(bfs_error(ret)))
print_bfs_bug(ret);
return ret;
}
/*
* Prove that the dependency graph starting at <src> can not
* lead to <target>. If it can, there is a circle when adding
* <target> -> <src> dependency.
*
* Print an error and return BFS_RMATCH if it does.
*/
static noinline enum bfs_result
check_noncircular(struct held_lock *src, struct held_lock *target,
struct lock_trace **const trace)
{
enum bfs_result ret;
struct lock_list *target_entry;
struct lock_list src_entry;
bfs_init_root(&src_entry, src);
debug_atomic_inc(nr_cyclic_checks);
ret = check_path(target, &src_entry, hlock_conflict, &target_entry);
if (unlikely(ret == BFS_RMATCH)) {
if (!*trace) {
/*
* If save_trace fails here, the printing might
* trigger a WARN but because of the !nr_entries it
* should not do bad things.
*/
*trace = save_trace();
}
print_circular_bug(&src_entry, target_entry, src, target);
}
return ret;
}
#ifdef CONFIG_LOCKDEP_SMALL
/*
* Check that the dependency graph starting at <src> can lead to
* <target> or not. If it can, <src> -> <target> dependency is already
* in the graph.
*
* Return BFS_RMATCH if it does, or BFS_RMATCH if it does not, return BFS_E* if
* any error appears in the bfs search.
*/
static noinline enum bfs_result
check_redundant(struct held_lock *src, struct held_lock *target)
{
enum bfs_result ret;
struct lock_list *target_entry;
struct lock_list src_entry;
bfs_init_root(&src_entry, src);
/*
* Special setup for check_redundant().
*
* To report redundant, we need to find a strong dependency path that
* is equal to or stronger than <src> -> <target>. So if <src> is E,
* we need to let __bfs() only search for a path starting at a -(E*)->,
* we achieve this by setting the initial node's ->only_xr to true in
* that case. And if <prev> is S, we set initial ->only_xr to false
* because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
*/
src_entry.only_xr = src->read == 0;
debug_atomic_inc(nr_redundant_checks);
ret = check_path(target, &src_entry, hlock_equal, &target_entry);
if (ret == BFS_RMATCH)
debug_atomic_inc(nr_redundant);
return ret;
}
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
static inline bool usage_accumulate(struct lock_list *entry, void *mask)
{
*(unsigned long *)mask |= entry->class->usage_mask;
return false;
}
/*
* Forwards and backwards subgraph searching, for the purposes of
* proving that two subgraphs can be connected by a new dependency
* without creating any illegal irq-safe -> irq-unsafe lock dependency.
*/
static inline bool usage_match(struct lock_list *entry, void *mask)
{
return !!(entry->class->usage_mask & *(unsigned long *)mask);
}
/*
* Find a node in the forwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*
* Return BFS_MATCH if such a node exists in the subgraph, and put that node
* into *@target_entry.
*/
static enum bfs_result
find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
struct lock_list **target_entry)
{
enum bfs_result result;
debug_atomic_inc(nr_find_usage_forwards_checks);
result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);
return result;
}
/*
* Find a node in the backwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*/
static enum bfs_result
find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
struct lock_list **target_entry)
{
enum bfs_result result;
debug_atomic_inc(nr_find_usage_backwards_checks);
result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);
return result;
}
static void print_lock_class_header(struct lock_class *class, int depth)
{
int bit;
printk("%*s->", depth, "");
print_lock_name(class);
#ifdef CONFIG_DEBUG_LOCKDEP
printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
#endif
printk(KERN_CONT " {\n");
for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
if (class->usage_mask & (1 << bit)) {
int len = depth;
len += printk("%*s %s", depth, "", usage_str[bit]);
len += printk(KERN_CONT " at:\n");
print_lock_trace(class->usage_traces[bit], len);
}
}
printk("%*s }\n", depth, "");
printk("%*s ... key at: [<%px>] %pS\n",
depth, "", class->key, class->key);
}
/*
* printk the shortest lock dependencies from @start to @end in reverse order:
*/
static void __used
print_shortest_lock_dependencies(struct lock_list *leaf,
struct lock_list *root)
{
struct lock_list *entry = leaf;
int depth;
/*compute depth from generated tree by BFS*/
depth = get_lock_depth(leaf);
do {
print_lock_class_header(entry->class, depth);
printk("%*s ... acquired at:\n", depth, "");
print_lock_trace(entry->trace, 2);
printk("\n");
if (depth == 0 && (entry != root)) {
printk("lockdep:%s bad path found in chain graph\n", __func__);
break;
}
entry = get_lock_parent(entry);
depth--;
} while (entry && (depth >= 0));
}
static void
print_irq_lock_scenario(struct lock_list *safe_entry,
struct lock_list *unsafe_entry,
struct lock_class *prev_class,
struct lock_class *next_class)
{
struct lock_class *safe_class = safe_entry->class;
struct lock_class *unsafe_class = unsafe_entry->class;
struct lock_class *middle_class = prev_class;
if (middle_class == safe_class)
middle_class = next_class;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
if (middle_class != unsafe_class) {
printk("Chain exists of:\n ");
__print_lock_name(safe_class);
printk(KERN_CONT " --> ");
__print_lock_name(middle_class);
printk(KERN_CONT " --> ");
__print_lock_name(unsafe_class);
printk(KERN_CONT "\n\n");
}
printk(" Possible interrupt unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
__print_lock_name(unsafe_class);
printk(KERN_CONT ");\n");
printk(" local_irq_disable();\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(middle_class);
printk(KERN_CONT ");\n");
printk(" <Interrupt>\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
static void
print_bad_irq_dependency(struct task_struct *curr,
struct lock_list *prev_root,
struct lock_list *next_root,
struct lock_list *backwards_entry,
struct lock_list *forwards_entry,
struct held_lock *prev,
struct held_lock *next,
enum lock_usage_bit bit1,
enum lock_usage_bit bit2,
const char *irqclass)
{
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
pr_warn("\n");
pr_warn("=====================================================\n");
pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
irqclass, irqclass);
print_kernel_ident();
pr_warn("-----------------------------------------------------\n");
pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
curr->comm, task_pid_nr(curr),
lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
lockdep_hardirqs_enabled(),
curr->softirqs_enabled);
print_lock(next);
pr_warn("\nand this task is already holding:\n");
print_lock(prev);
pr_warn("which would create a new lock dependency:\n");
print_lock_name(hlock_class(prev));
pr_cont(" ->");
print_lock_name(hlock_class(next));
pr_cont("\n");
pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
irqclass);
print_lock_name(backwards_entry->class);
pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
print_lock_name(forwards_entry->class);
pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
pr_warn("...");
print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
pr_warn("\nother info that might help us debug this:\n\n");
print_irq_lock_scenario(backwards_entry, forwards_entry,
hlock_class(prev), hlock_class(next));
lockdep_print_held_locks(curr);
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
prev_root->trace = save_trace();
if (!prev_root->trace)
return;
print_shortest_lock_dependencies(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired");
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
next_root->trace = save_trace();
if (!next_root->trace)
return;
print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static const char *state_names[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE),
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static const char *state_rnames[] = {
#define LOCKDEP_STATE(__STATE) \
__stringify(__STATE)"-READ",
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static inline const char *state_name(enum lock_usage_bit bit)
{
if (bit & LOCK_USAGE_READ_MASK)
return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
else
return state_names[bit >> LOCK_USAGE_DIR_MASK];
}
/*
* The bit number is encoded like:
*
* bit0: 0 exclusive, 1 read lock
* bit1: 0 used in irq, 1 irq enabled
* bit2-n: state
*/
static int exclusive_bit(int new_bit)
{
int state = new_bit & LOCK_USAGE_STATE_MASK;
int dir = new_bit & LOCK_USAGE_DIR_MASK;
/*
* keep state, bit flip the direction and strip read.
*/
return state | (dir ^ LOCK_USAGE_DIR_MASK);
}
/*
* Observe that when given a bitmask where each bitnr is encoded as above, a
* right shift of the mask transforms the individual bitnrs as -1 and
* conversely, a left shift transforms into +1 for the individual bitnrs.
*
* So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
* create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
* instead by subtracting the bit number by 2, or shifting the mask right by 2.
*
* Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
*
* So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
* all bits set) and recompose with bitnr1 flipped.
*/
static unsigned long invert_dir_mask(unsigned long mask)
{
unsigned long excl = 0;
/* Invert dir */
excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
return excl;
}
/*
* As above, we clear bitnr0 (LOCK_*_READ off) with bitmask ops. First, for all
* bits with bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*).
* And then mask out all bitnr0.
*/
static unsigned long exclusive_mask(unsigned long mask)
{
unsigned long excl = invert_dir_mask(mask);
/* Strip read */
excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
excl &= ~LOCKF_IRQ_READ;
return excl;
}
/*
* Retrieve the _possible_ original mask to which @mask is
* exclusive. Ie: this is the opposite of exclusive_mask().
* Note that 2 possible original bits can match an exclusive
* bit: one has LOCK_USAGE_READ_MASK set, the other has it
* cleared. So both are returned for each exclusive bit.
*/
static unsigned long original_mask(unsigned long mask)
{
unsigned long excl = invert_dir_mask(mask);
/* Include read in existing usages */
excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
return excl;
}
/*
* Find the first pair of bit match between an original
* usage mask and an exclusive usage mask.
*/
static int find_exclusive_match(unsigned long mask,
unsigned long excl_mask,
enum lock_usage_bit *bitp,
enum lock_usage_bit *excl_bitp)
{
int bit, excl;
for_each_set_bit(bit, &mask, LOCK_USED) {
excl = exclusive_bit(bit);
if (excl_mask & lock_flag(excl)) {
*bitp = bit;
*excl_bitp = excl;
return 0;
}
}
return -1;
}
/*
* Prove that the new dependency does not connect a hardirq-safe(-read)
* lock with a hardirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
{
unsigned long usage_mask = 0, forward_mask, backward_mask;
enum lock_usage_bit forward_bit = 0, backward_bit = 0;
struct lock_list *target_entry1;
struct lock_list *target_entry;
struct lock_list this, that;
enum bfs_result ret;
/*
* Step 1: gather all hard/soft IRQs usages backward in an
* accumulated usage mask.
*/
this.parent = NULL;
this.class = hlock_class(prev);
ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
usage_mask &= LOCKF_USED_IN_IRQ_ALL;
if (!usage_mask)
return 1;
/*
* Step 2: find exclusive uses forward that match the previous
* backward accumulated mask.
*/
forward_mask = exclusive_mask(usage_mask);
that.parent = NULL;
that.class = hlock_class(next);
ret = find_usage_forwards(&that, forward_mask, &target_entry1);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (ret == BFS_RNOMATCH)
return 1;
/*
* Step 3: we found a bad match! Now retrieve a lock from the backward
* list whose usage mask matches the exclusive usage mask from the
* lock found on the forward list.
*/
backward_mask = original_mask(target_entry1->class->usage_mask);
ret = find_usage_backwards(&this, backward_mask, &target_entry);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
return 1;
/*
* Step 4: narrow down to a pair of incompatible usage bits
* and report it.
*/
ret = find_exclusive_match(target_entry->class->usage_mask,
target_entry1->class->usage_mask,
&backward_bit, &forward_bit);
if (DEBUG_LOCKS_WARN_ON(ret == -1))
return 1;
print_bad_irq_dependency(curr, &this, &that,
target_entry, target_entry1,
prev, next,
backward_bit, forward_bit,
state_name(backward_bit));
return 0;
}
#else
static inline int check_irq_usage(struct task_struct *curr,
struct held_lock *prev, struct held_lock *next)
{
return 1;
}
#endif /* CONFIG_TRACE_IRQFLAGS */
static void inc_chains(int irq_context)
{
if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
nr_hardirq_chains++;
else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
nr_softirq_chains++;
else
nr_process_chains++;
}
static void dec_chains(int irq_context)
{
if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
nr_hardirq_chains--;
else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
nr_softirq_chains--;
else
nr_process_chains--;
}
static void
print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
{
struct lock_class *next = hlock_class(nxt);
struct lock_class *prev = hlock_class(prv);
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0\n");
printk(" ----\n");
printk(" lock(");
__print_lock_name(prev);
printk(KERN_CONT ");\n");
printk(" lock(");
__print_lock_name(next);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
printk(" May be due to missing lock nesting notation\n\n");
}
static void
print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
{
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
pr_warn("\n");
pr_warn("============================================\n");
pr_warn("WARNING: possible recursive locking detected\n");
print_kernel_ident();
pr_warn("--------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(next);
pr_warn("\nbut task is already holding lock:\n");
print_lock(prev);
pr_warn("\nother info that might help us debug this:\n");
print_deadlock_scenario(next, prev);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
/*
* Check whether we are holding such a class already.
*
* (Note that this has to be done separately, because the graph cannot
* detect such classes of deadlocks.)
*
* Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
*/
static int
check_deadlock(struct task_struct *curr, struct held_lock *next)
{
struct held_lock *prev;
struct held_lock *nest = NULL;
int i;
for (i = 0; i < curr->lockdep_depth; i++) {
prev = curr->held_locks + i;
if (prev->instance == next->nest_lock)
nest = prev;
if (hlock_class(prev) != hlock_class(next))
continue;
/*
* Allow read-after-read recursion of the same
* lock class (i.e. read_lock(lock)+read_lock(lock)):
*/
if ((next->read == 2) && prev->read)
return 2;
/*
* We're holding the nest_lock, which serializes this lock's
* nesting behaviour.
*/
if (nest)
return 2;
print_deadlock_bug(curr, prev, next);
return 0;
}
return 1;
}
/*
* There was a chain-cache miss, and we are about to add a new dependency
* to a previous lock. We validate the following rules:
*
* - would the adding of the <prev> -> <next> dependency create a
* circular dependency in the graph? [== circular deadlock]
*
* - does the new prev->next dependency connect any hardirq-safe lock
* (in the full backwards-subgraph starting at <prev>) with any
* hardirq-unsafe lock (in the full forwards-subgraph starting at
* <next>)? [== illegal lock inversion with hardirq contexts]
*
* - does the new prev->next dependency connect any softirq-safe lock
* (in the full backwards-subgraph starting at <prev>) with any
* softirq-unsafe lock (in the full forwards-subgraph starting at
* <next>)? [== illegal lock inversion with softirq contexts]
*
* any of these scenarios could lead to a deadlock.
*
* Then if all the validations pass, we add the forwards and backwards
* dependency.
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next, u16 distance,
struct lock_trace **const trace)
{
struct lock_list *entry;
enum bfs_result ret;
if (!hlock_class(prev)->key || !hlock_class(next)->key) {
/*
* The warning statements below may trigger a use-after-free
* of the class name. It is better to trigger a use-after free
* and to have the class name most of the time instead of not
* having the class name available.
*/
WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
"Detected use-after-free of lock class %px/%s\n",
hlock_class(prev),
hlock_class(prev)->name);
WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
"Detected use-after-free of lock class %px/%s\n",
hlock_class(next),
hlock_class(next)->name);
return 2;
}
/*
* Prove that the new <prev> -> <next> dependency would not
* create a circular dependency in the graph. (We do this by
* a breadth-first search into the graph starting at <next>,
* and check whether we can reach <prev>.)
*
* The search is limited by the size of the circular queue (i.e.,
* MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
* in the graph whose neighbours are to be checked.
*/
ret = check_noncircular(next, prev, trace);
if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
return 0;
if (!check_irq_usage(curr, prev, next))
return 0;
/*
* For recursive read-locks we do all the dependency checks,
* but we dont store read-triggered dependencies (only
* write-triggered dependencies). This ensures that only the
* write-side dependencies matter, and that if for example a
* write-lock never takes any other locks, then the reads are
* equivalent to a NOP.
*/
if (next->read == 2 || prev->read == 2)
return 1;
/*
* Is the <prev> -> <next> dependency already present?
*
* (this may occur even though this is a new chain: consider
* e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
* chains - the second one will be new, but L1 already has
* L2 added to its dependency list, due to the first chain.)
*/
list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
if (entry->class == hlock_class(next)) {
if (distance == 1)
entry->distance = 1;
entry->dep |= calc_dep(prev, next);
/*
* Also, update the reverse dependency in @next's
* ->locks_before list.
*
* Here we reuse @entry as the cursor, which is fine
* because we won't go to the next iteration of the
* outer loop:
*
* For normal cases, we return in the inner loop.
*
* If we fail to return, we have inconsistency, i.e.
* <prev>::locks_after contains <next> while
* <next>::locks_before doesn't contain <prev>. In
* that case, we return after the inner and indicate
* something is wrong.
*/
list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
if (entry->class == hlock_class(prev)) {
if (distance == 1)
entry->distance = 1;
entry->dep |= calc_depb(prev, next);
return 1;
}
}
/* <prev> is not found in <next>::locks_before */
return 0;
}
}
#ifdef CONFIG_LOCKDEP_SMALL
/*
* Is the <prev> -> <next> link redundant?
*/
ret = check_redundant(prev, next);
if (bfs_error(ret))
return 0;
else if (ret == BFS_RMATCH)
return 2;
#endif
if (!*trace) {
*trace = save_trace();
if (!*trace)
return 0;
}
/*
* Ok, all validations passed, add the new lock
* to the previous lock's dependency list:
*/
ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
&hlock_class(prev)->locks_after,
next->acquire_ip, distance,
calc_dep(prev, next),
*trace);
if (!ret)
return 0;
ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
&hlock_class(next)->locks_before,
next->acquire_ip, distance,
calc_depb(prev, next),
*trace);
if (!ret)
return 0;
return 2;
}
/*
* Add the dependency to all directly-previous locks that are 'relevant'.
* The ones that are relevant are (in increasing distance from curr):
* all consecutive trylock entries and the final non-trylock entry - or
* the end of this context's lock-chain - whichever comes first.
*/
static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
struct lock_trace *trace = NULL;
int depth = curr->lockdep_depth;
struct held_lock *hlock;
/*
* Debugging checks.
*
* Depth must not be zero for a non-head lock:
*/
if (!depth)
goto out_bug;
/*
* At least two relevant locks must exist for this
* to be a head:
*/
if (curr->held_locks[depth].irq_context !=
curr->held_locks[depth-1].irq_context)
goto out_bug;
for (;;) {
u16 distance = curr->lockdep_depth - depth + 1;
hlock = curr->held_locks + depth - 1;
/*
* Only non-recursive-read entries get new dependencies
* added:
*/
if (hlock->read != 2 && hlock->check) {
int ret = check_prev_add(curr, hlock, next, distance,
&trace);
if (!ret)
return 0;
/*
* Stop after the first non-trylock entry,
* as non-trylock entries have added their
* own direct dependencies already, so this
* lock is connected to them indirectly:
*/
if (!hlock->trylock)
break;
}
depth--;
/*
* End of lock-stack?
*/
if (!depth)
break;
/*
* Stop the search if we cross into another context:
*/
if (curr->held_locks[depth].irq_context !=
curr->held_locks[depth-1].irq_context)
break;
}
return 1;
out_bug:
if (!debug_locks_off_graph_unlock())
return 0;
/*
* Clearly we all shouldn't be here, but since we made it we
* can reliable say we messed up our state. See the above two
* gotos for reasons why we could possibly end up here.
*/
WARN_ON(1);
return 0;
}
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
unsigned long nr_zapped_lock_chains;
unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
/*
* The first 2 chain_hlocks entries in the chain block in the bucket
* list contains the following meta data:
*
* entry[0]:
* Bit 15 - always set to 1 (it is not a class index)
* Bits 0-14 - upper 15 bits of the next block index
* entry[1] - lower 16 bits of next block index
*
* A next block index of all 1 bits means it is the end of the list.
*
* On the unsized bucket (bucket-0), the 3rd and 4th entries contain
* the chain block size:
*
* entry[2] - upper 16 bits of the chain block size
* entry[3] - lower 16 bits of the chain block size
*/
#define MAX_CHAIN_BUCKETS 16
#define CHAIN_BLK_FLAG (1U << 15)
#define CHAIN_BLK_LIST_END 0xFFFFU
static int chain_block_buckets[MAX_CHAIN_BUCKETS];
static inline int size_to_bucket(int size)
{
if (size > MAX_CHAIN_BUCKETS)
return 0;
return size - 1;
}
/*
* Iterate all the chain blocks in a bucket.
*/
#define for_each_chain_block(bucket, prev, curr) \
for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
(curr) >= 0; \
(prev) = (curr), (curr) = chain_block_next(curr))
/*
* next block or -1
*/
static inline int chain_block_next(int offset)
{
int next = chain_hlocks[offset];
WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
if (next == CHAIN_BLK_LIST_END)
return -1;
next &= ~CHAIN_BLK_FLAG;
next <<= 16;
next |= chain_hlocks[offset + 1];
return next;
}
/*
* bucket-0 only
*/
static inline int chain_block_size(int offset)
{
return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
}
static inline void init_chain_block(int offset, int next, int bucket, int size)
{
chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
chain_hlocks[offset + 1] = (u16)next;
if (size && !bucket) {
chain_hlocks[offset + 2] = size >> 16;
chain_hlocks[offset + 3] = (u16)size;
}
}
static inline void add_chain_block(int offset, int size)
{
int bucket = size_to_bucket(size);
int next = chain_block_buckets[bucket];
int prev, curr;
if (unlikely(size < 2)) {
/*
* We can't store single entries on the freelist. Leak them.
*
* One possible way out would be to uniquely mark them, other
* than with CHAIN_BLK_FLAG, such that we can recover them when
* the block before it is re-added.
*/
if (size)
nr_lost_chain_hlocks++;
return;
}
nr_free_chain_hlocks += size;
if (!bucket) {
nr_large_chain_blocks++;
/*
* Variable sized, sort large to small.
*/
for_each_chain_block(0, prev, curr) {
if (size >= chain_block_size(curr))
break;
}
init_chain_block(offset, curr, 0, size);
if (prev < 0)
chain_block_buckets[0] = offset;
else
init_chain_block(prev, offset, 0, 0);
return;
}
/*
* Fixed size, add to head.
*/
init_chain_block(offset, next, bucket, size);
chain_block_buckets[bucket] = offset;
}
/*
* Only the first block in the list can be deleted.
*
* For the variable size bucket[0], the first block (the largest one) is
* returned, broken up and put back into the pool. So if a chain block of
* length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
* queued up after the primordial chain block and never be used until the
* hlock entries in the primordial chain block is almost used up. That
* causes fragmentation and reduce allocation efficiency. That can be
* monitored by looking at the "large chain blocks" number in lockdep_stats.
*/
static inline void del_chain_block(int bucket, int size, int next)
{
nr_free_chain_hlocks -= size;
chain_block_buckets[bucket] = next;
if (!bucket)
nr_large_chain_blocks--;
}
static void init_chain_block_buckets(void)
{
int i;
for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
chain_block_buckets[i] = -1;
add_chain_block(0, ARRAY_SIZE(chain_hlocks));
}
/*
* Return offset of a chain block of the right size or -1 if not found.
*
* Fairly simple worst-fit allocator with the addition of a number of size
* specific free lists.
*/
static int alloc_chain_hlocks(int req)
{
int bucket, curr, size;
/*
* We rely on the MSB to act as an escape bit to denote freelist
* pointers. Make sure this bit isn't set in 'normal' class_idx usage.
*/
BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
init_data_structures_once();
if (nr_free_chain_hlocks < req)
return -1;
/*
* We require a minimum of 2 (u16) entries to encode a freelist
* 'pointer'.
*/
req = max(req, 2);
bucket = size_to_bucket(req);
curr = chain_block_buckets[bucket];
if (bucket) {
if (curr >= 0) {
del_chain_block(bucket, req, chain_block_next(curr));
return curr;
}
/* Try bucket 0 */
curr = chain_block_buckets[0];
}
/*
* The variable sized freelist is sorted by size; the first entry is
* the largest. Use it if it fits.
*/
if (curr >= 0) {
size = chain_block_size(curr);
if (likely(size >= req)) {
del_chain_block(0, size, chain_block_next(curr));
add_chain_block(curr + req, size - req);
return curr;
}
}
/*
* Last resort, split a block in a larger sized bucket.
*/
for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
bucket = size_to_bucket(size);
curr = chain_block_buckets[bucket];
if (curr < 0)
continue;
del_chain_block(bucket, size, chain_block_next(curr));
add_chain_block(curr + req, size - req);
return curr;
}
return -1;
}
static inline void free_chain_hlocks(int base, int size)
{
add_chain_block(base, max(size, 2));
}
struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
{
return lock_classes + chain_hlocks[chain->base + i];
}
/*
* Returns the index of the first held_lock of the current chain
*/
static inline int get_first_held_lock(struct task_struct *curr,
struct held_lock *hlock)
{
int i;
struct held_lock *hlock_curr;
for (i = curr->lockdep_depth - 1; i >= 0; i--) {
hlock_curr = curr->held_locks + i;
if (hlock_curr->irq_context != hlock->irq_context)
break;
}
return ++i;
}
#ifdef CONFIG_DEBUG_LOCKDEP
/*
* Returns the next chain_key iteration
*/
static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
{
u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
printk(" class_idx:%d -> chain_key:%016Lx",
class_idx,
(unsigned long long)new_chain_key);
return new_chain_key;
}
static void
print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
{
struct held_lock *hlock;
u64 chain_key = INITIAL_CHAIN_KEY;
int depth = curr->lockdep_depth;
int i = get_first_held_lock(curr, hlock_next);
printk("depth: %u (irq_context %u)\n", depth - i + 1,
hlock_next->irq_context);
for (; i < depth; i++) {
hlock = curr->held_locks + i;
chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
print_lock(hlock);
}
print_chain_key_iteration(hlock_next->class_idx, chain_key);
print_lock(hlock_next);
}
static void print_chain_keys_chain(struct lock_chain *chain)
{
int i;
u64 chain_key = INITIAL_CHAIN_KEY;
int class_id;
printk("depth: %u\n", chain->depth);
for (i = 0; i < chain->depth; i++) {
class_id = chain_hlocks[chain->base + i];
chain_key = print_chain_key_iteration(class_id, chain_key);
print_lock_name(lock_classes + class_id);
printk("\n");
}
}
static void print_collision(struct task_struct *curr,
struct held_lock *hlock_next,
struct lock_chain *chain)
{
pr_warn("\n");
pr_warn("============================\n");
pr_warn("WARNING: chain_key collision\n");
print_kernel_ident();
pr_warn("----------------------------\n");
pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
pr_warn("Hash chain already cached but the contents don't match!\n");
pr_warn("Held locks:");
print_chain_keys_held_locks(curr, hlock_next);
pr_warn("Locks in cached chain:");
print_chain_keys_chain(chain);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
#endif
/*
* Checks whether the chain and the current held locks are consistent
* in depth and also in content. If they are not it most likely means
* that there was a collision during the calculation of the chain_key.
* Returns: 0 not passed, 1 passed
*/
static int check_no_collision(struct task_struct *curr,
struct held_lock *hlock,
struct lock_chain *chain)
{
#ifdef CONFIG_DEBUG_LOCKDEP
int i, j, id;
i = get_first_held_lock(curr, hlock);
if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
print_collision(curr, hlock, chain);
return 0;
}
for (j = 0; j < chain->depth - 1; j++, i++) {
id = curr->held_locks[i].class_idx;
if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
print_collision(curr, hlock, chain);
return 0;
}
}
#endif
return 1;
}
/*
* Given an index that is >= -1, return the index of the next lock chain.
* Return -2 if there is no next lock chain.
*/
long lockdep_next_lockchain(long i)
{
i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
return i < ARRAY_SIZE(lock_chains) ? i : -2;
}
unsigned long lock_chain_count(void)
{
return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
}
/* Must be called with the graph lock held. */
static struct lock_chain *alloc_lock_chain(void)
{
int idx = find_first_zero_bit(lock_chains_in_use,
ARRAY_SIZE(lock_chains));
if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
return NULL;
__set_bit(idx, lock_chains_in_use);
return lock_chains + idx;
}
/*
* Adds a dependency chain into chain hashtable. And must be called with
* graph_lock held.
*
* Return 0 if fail, and graph_lock is released.
* Return 1 if succeed, with graph_lock held.
*/
static inline int add_chain_cache(struct task_struct *curr,
struct held_lock *hlock,
u64 chain_key)
{
struct lock_class *class = hlock_class(hlock);
struct hlist_head *hash_head = chainhashentry(chain_key);
struct lock_chain *chain;
int i, j;
/*
* The caller must hold the graph lock, ensure we've got IRQs
* disabled to make this an IRQ-safe lock.. for recursion reasons
* lockdep won't complain about its own locking errors.
*/
if (lockdep_assert_locked())
return 0;
chain = alloc_lock_chain();
if (!chain) {
if (!debug_locks_off_graph_unlock())
return 0;
print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
dump_stack();
return 0;
}
chain->chain_key = chain_key;
chain->irq_context = hlock->irq_context;
i = get_first_held_lock(curr, hlock);
chain->depth = curr->lockdep_depth + 1 - i;
BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
j = alloc_chain_hlocks(chain->depth);
if (j < 0) {
if (!debug_locks_off_graph_unlock())
return 0;
print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
dump_stack();
return 0;
}
chain->base = j;
for (j = 0; j < chain->depth - 1; j++, i++) {
int lock_id = curr->held_locks[i].class_idx;
chain_hlocks[chain->base + j] = lock_id;
}
chain_hlocks[chain->base + j] = class - lock_classes;
hlist_add_head_rcu(&chain->entry, hash_head);
debug_atomic_inc(chain_lookup_misses);
inc_chains(chain->irq_context);
return 1;
}
/*
* Look up a dependency chain. Must be called with either the graph lock or
* the RCU read lock held.
*/
static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
{
struct hlist_head *hash_head = chainhashentry(chain_key);
struct lock_chain *chain;
hlist_for_each_entry_rcu(chain, hash_head, entry) {
if (READ_ONCE(chain->chain_key) == chain_key) {
debug_atomic_inc(chain_lookup_hits);
return chain;
}
}
return NULL;
}
/*
* If the key is not present yet in dependency chain cache then
* add it and return 1 - in this case the new dependency chain is
* validated. If the key is already hashed, return 0.
* (On return with 1 graph_lock is held.)
*/
static inline int lookup_chain_cache_add(struct task_struct *curr,
struct held_lock *hlock,
u64 chain_key)
{
struct lock_class *class = hlock_class(hlock);
struct lock_chain *chain = lookup_chain_cache(chain_key);
if (chain) {
cache_hit:
if (!check_no_collision(curr, hlock, chain))
return 0;
if (very_verbose(class)) {
printk("\nhash chain already cached, key: "
"%016Lx tail class: [%px] %s\n",
(unsigned long long)chain_key,
class->key, class->name);
}
return 0;
}
if (very_verbose(class)) {
printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
(unsigned long long)chain_key, class->key, class->name);
}
if (!graph_lock())
return 0;
/*
* We have to walk the chain again locked - to avoid duplicates:
*/
chain = lookup_chain_cache(chain_key);
if (chain) {
graph_unlock();
goto cache_hit;
}
if (!add_chain_cache(curr, hlock, chain_key))
return 0;
return 1;
}
static int validate_chain(struct task_struct *curr,
struct held_lock *hlock,
int chain_head, u64 chain_key)
{
/*
* Trylock needs to maintain the stack of held locks, but it
* does not add new dependencies, because trylock can be done
* in any order.
*
* We look up the chain_key and do the O(N^2) check and update of
* the dependencies only if this is a new dependency chain.
* (If lookup_chain_cache_add() return with 1 it acquires
* graph_lock for us)
*/
if (!hlock->trylock && hlock->check &&
lookup_chain_cache_add(curr, hlock, chain_key)) {
/*
* Check whether last held lock:
*
* - is irq-safe, if this lock is irq-unsafe
* - is softirq-safe, if this lock is hardirq-unsafe
*
* And check whether the new lock's dependency graph
* could lead back to the previous lock:
*
* - within the current held-lock stack
* - across our accumulated lock dependency records
*
* any of these scenarios could lead to a deadlock.
*/
/*
* The simple case: does the current hold the same lock
* already?
*/
int ret = check_deadlock(curr, hlock);
if (!ret)
return 0;
/*
* Mark recursive read, as we jump over it when
* building dependencies (just like we jump over
* trylock entries):
*/
if (ret == 2)
hlock->read = 2;
/*
* Add dependency only if this lock is not the head
* of the chain, and if it's not a secondary read-lock:
*/
if (!chain_head && ret != 2) {
if (!check_prevs_add(curr, hlock))
return 0;
}
graph_unlock();
} else {
/* after lookup_chain_cache_add(): */
if (unlikely(!debug_locks))
return 0;
}
return 1;
}
#else
static inline int validate_chain(struct task_struct *curr,
struct held_lock *hlock,
int chain_head, u64 chain_key)
{
return 1;
}
static void init_chain_block_buckets(void) { }
#endif /* CONFIG_PROVE_LOCKING */
/*
* We are building curr_chain_key incrementally, so double-check
* it from scratch, to make sure that it's done correctly:
*/
static void check_chain_key(struct task_struct *curr)
{
#ifdef CONFIG_DEBUG_LOCKDEP
struct held_lock *hlock, *prev_hlock = NULL;
unsigned int i;
u64 chain_key = INITIAL_CHAIN_KEY;
for (i = 0; i < curr->lockdep_depth; i++) {
hlock = curr->held_locks + i;
if (chain_key != hlock->prev_chain_key) {
debug_locks_off();
/*
* We got mighty confused, our chain keys don't match
* with what we expect, someone trample on our task state?
*/
WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
curr->lockdep_depth, i,
(unsigned long long)chain_key,
(unsigned long long)hlock->prev_chain_key);
return;
}
/*
* hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
* it registered lock class index?
*/
if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
return;
if (prev_hlock && (prev_hlock->irq_context !=
hlock->irq_context))
chain_key = INITIAL_CHAIN_KEY;
chain_key = iterate_chain_key(chain_key, hlock->class_idx);
prev_hlock = hlock;
}
if (chain_key != curr->curr_chain_key) {
debug_locks_off();
/*
* More smoking hash instead of calculating it, damn see these
* numbers float.. I bet that a pink elephant stepped on my memory.
*/
WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
curr->lockdep_depth, i,
(unsigned long long)chain_key,
(unsigned long long)curr->curr_chain_key);
}
#endif
}
#ifdef CONFIG_PROVE_LOCKING
static int mark_lock(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit);
static void print_usage_bug_scenario(struct held_lock *lock)
{
struct lock_class *class = hlock_class(lock);
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0\n");
printk(" ----\n");
printk(" lock(");
__print_lock_name(class);
printk(KERN_CONT ");\n");
printk(" <Interrupt>\n");
printk(" lock(");
__print_lock_name(class);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
static void
print_usage_bug(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
{
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
pr_warn("\n");
pr_warn("================================\n");
pr_warn("WARNING: inconsistent lock state\n");
print_kernel_ident();
pr_warn("--------------------------------\n");
pr_warn("inconsistent {%s} -> {%s} usage.\n",
usage_str[prev_bit], usage_str[new_bit]);
pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
curr->comm, task_pid_nr(curr),
lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
lockdep_hardirqs_enabled(),
lockdep_softirqs_enabled(curr));
print_lock(this);
pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
print_irqtrace_events(curr);
pr_warn("\nother info that might help us debug this:\n");
print_usage_bug_scenario(this);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
/*
* Print out an error if an invalid bit is set:
*/
static inline int
valid_state(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
{
if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
print_usage_bug(curr, this, bad_bit, new_bit);
return 0;
}
return 1;
}
/*
* print irq inversion bug:
*/
static void
print_irq_inversion_bug(struct task_struct *curr,
struct lock_list *root, struct lock_list *other,
struct held_lock *this, int forwards,
const char *irqclass)
{
struct lock_list *entry = other;
struct lock_list *middle = NULL;
int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
pr_warn("\n");
pr_warn("========================================================\n");
pr_warn("WARNING: possible irq lock inversion dependency detected\n");
print_kernel_ident();
pr_warn("--------------------------------------------------------\n");
pr_warn("%s/%d just changed the state of lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(this);
if (forwards)
pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
else
pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
print_lock_name(other->class);
pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
pr_warn("\nother info that might help us debug this:\n");
/* Find a middle lock (if one exists) */
depth = get_lock_depth(other);
do {
if (depth == 0 && (entry != root)) {
pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
break;
}
middle = entry;
entry = get_lock_parent(entry);
depth--;
} while (entry && entry != root && (depth >= 0));
if (forwards)
print_irq_lock_scenario(root, other,
middle ? middle->class : root->class, other->class);
else
print_irq_lock_scenario(other, root,
middle ? middle->class : other->class, root->class);
lockdep_print_held_locks(curr);
pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
root->trace = save_trace();
if (!root->trace)
return;
print_shortest_lock_dependencies(other, root);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
/*
* Prove that in the forwards-direction subgraph starting at <this>
* there is no lock matching <mask>:
*/
static int
check_usage_forwards(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit bit, const char *irqclass)
{
enum bfs_result ret;
struct lock_list root;
struct lock_list *target_entry;
bfs_init_root(&root, this);
ret = find_usage_forwards(&root, lock_flag(bit), &target_entry);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (ret == BFS_RNOMATCH)
return 1;
print_irq_inversion_bug(curr, &root, target_entry,
this, 1, irqclass);
return 0;
}
/*
* Prove that in the backwards-direction subgraph starting at <this>
* there is no lock matching <mask>:
*/
static int
check_usage_backwards(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit bit, const char *irqclass)
{
enum bfs_result ret;
struct lock_list root;
struct lock_list *target_entry;
bfs_init_rootb(&root, this);
ret = find_usage_backwards(&root, lock_flag(bit), &target_entry);
if (bfs_error(ret)) {
print_bfs_bug(ret);
return 0;
}
if (ret == BFS_RNOMATCH)
return 1;
print_irq_inversion_bug(curr, &root, target_entry,
this, 0, irqclass);
return 0;
}
void print_irqtrace_events(struct task_struct *curr)
{
const struct irqtrace_events *trace = &curr->irqtrace;
printk("irq event stamp: %u\n", trace->irq_events);
printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
(void *)trace->hardirq_enable_ip);
printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
(void *)trace->hardirq_disable_ip);
printk("softirqs last enabled at (%u): [<%px>] %pS\n",
trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
(void *)trace->softirq_enable_ip);
printk("softirqs last disabled at (%u): [<%px>] %pS\n",
trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
(void *)trace->softirq_disable_ip);
}
static int HARDIRQ_verbose(struct lock_class *class)
{
#if HARDIRQ_VERBOSE
return class_filter(class);
#endif
return 0;
}
static int SOFTIRQ_verbose(struct lock_class *class)
{
#if SOFTIRQ_VERBOSE
return class_filter(class);
#endif
return 0;
}
#define STRICT_READ_CHECKS 1
static int (*state_verbose_f[])(struct lock_class *class) = {
#define LOCKDEP_STATE(__STATE) \
__STATE##_verbose,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};
static inline int state_verbose(enum lock_usage_bit bit,
struct lock_class *class)
{
return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
}
typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
enum lock_usage_bit bit, const char *name);
static int
mark_lock_irq(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
int excl_bit = exclusive_bit(new_bit);
int read = new_bit & LOCK_USAGE_READ_MASK;
int dir = new_bit & LOCK_USAGE_DIR_MASK;
/*
* mark USED_IN has to look forwards -- to ensure no dependency
* has ENABLED state, which would allow recursion deadlocks.
*
* mark ENABLED has to look backwards -- to ensure no dependee
* has USED_IN state, which, again, would allow recursion deadlocks.
*/
check_usage_f usage = dir ?
check_usage_backwards : check_usage_forwards;
/*
* Validate that this particular lock does not have conflicting
* usage states.
*/
if (!valid_state(curr, this, new_bit, excl_bit))
return 0;
/*
* Validate that the lock dependencies don't have conflicting usage
* states.
*/
if ((!read || STRICT_READ_CHECKS) &&
!usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
return 0;
/*
* Check for read in write conflicts
*/
if (!read) {
if (!valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK))
return 0;
if (STRICT_READ_CHECKS &&
!usage(curr, this, excl_bit + LOCK_USAGE_READ_MASK,
state_name(new_bit + LOCK_USAGE_READ_MASK)))
return 0;
}
if (state_verbose(new_bit, hlock_class(this)))
return 2;
return 1;
}
/*
* Mark all held locks with a usage bit:
*/
static int
mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
{
struct held_lock *hlock;
int i;
for (i = 0; i < curr->lockdep_depth; i++) {
enum lock_usage_bit hlock_bit = base_bit;
hlock = curr->held_locks + i;
if (hlock->read)
hlock_bit += LOCK_USAGE_READ_MASK;
BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
if (!hlock->check)
continue;
if (!mark_lock(curr, hlock, hlock_bit))
return 0;
}
return 1;
}
/*
* Hardirqs will be enabled:
*/
static void __trace_hardirqs_on_caller(void)
{
struct task_struct *curr = current;
/*
* We are going to turn hardirqs on, so set the
* usage bit for all held locks:
*/
if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
return;
/*
* If we have softirqs enabled, then set the usage
* bit for all held locks. (disabled hardirqs prevented
* this bit from being set before)
*/
if (curr->softirqs_enabled)
mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
}
/**
* lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
* @ip: Caller address
*
* Invoked before a possible transition to RCU idle from exit to user or
* guest mode. This ensures that all RCU operations are done before RCU
* stops watching. After the RCU transition lockdep_hardirqs_on() has to be
* invoked to set the final state.
*/
void lockdep_hardirqs_on_prepare(unsigned long ip)
{
if (unlikely(!debug_locks))
return;
/*
* NMIs do not (and cannot) track lock dependencies, nothing to do.
*/
if (unlikely(in_nmi()))
return;
if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))
return;
if (unlikely(lockdep_hardirqs_enabled())) {
/*
* Neither irq nor preemption are disabled here
* so this is racy by nature but losing one hit
* in a stat is not a big deal.
*/
__debug_atomic_inc(redundant_hardirqs_on);
return;
}
/*
* We're enabling irqs and according to our state above irqs weren't
* already enabled, yet we find the hardware thinks they are in fact
* enabled.. someone messed up their IRQ state tracing.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
/*
* See the fine text that goes along with this variable definition.
*/
if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
return;
/*
* Can't allow enabling interrupts while in an interrupt handler,
* that's general bad form and such. Recursion, limited stack etc..
*/
if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
return;
current->hardirq_chain_key = current->curr_chain_key;
current->lockdep_recursion++;
__trace_hardirqs_on_caller();
lockdep_recursion_finish();
}
EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
void noinstr lockdep_hardirqs_on(unsigned long ip)
{
struct irqtrace_events *trace = &current->irqtrace;
if (unlikely(!debug_locks))
return;
/*
* NMIs can happen in the middle of local_irq_{en,dis}able() where the
* tracking state and hardware state are out of sync.
*
* NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
* and not rely on hardware state like normal interrupts.
*/
if (unlikely(in_nmi())) {
if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
return;
/*
* Skip:
* - recursion check, because NMI can hit lockdep;
* - hardware state check, because above;
* - chain_key check, see lockdep_hardirqs_on_prepare().
*/
goto skip_checks;
}
if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))
return;
if (lockdep_hardirqs_enabled()) {
/*
* Neither irq nor preemption are disabled here
* so this is racy by nature but losing one hit
* in a stat is not a big deal.
*/
__debug_atomic_inc(redundant_hardirqs_on);
return;
}
/*
* We're enabling irqs and according to our state above irqs weren't
* already enabled, yet we find the hardware thinks they are in fact
* enabled.. someone messed up their IRQ state tracing.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
/*
* Ensure the lock stack remained unchanged between
* lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
*/
DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
current->curr_chain_key);
skip_checks:
/* we'll do an OFF -> ON transition: */
__this_cpu_write(hardirqs_enabled, 1);
trace->hardirq_enable_ip = ip;
trace->hardirq_enable_event = ++trace->irq_events;
debug_atomic_inc(hardirqs_on_events);
}
EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
/*
* Hardirqs were disabled:
*/
void noinstr lockdep_hardirqs_off(unsigned long ip)
{
if (unlikely(!debug_locks))
return;
/*
* Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
* they will restore the software state. This ensures the software
* state is consistent inside NMIs as well.
*/
if (in_nmi()) {
if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
return;
} else if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK)
return;
/*
* So we're supposed to get called after you mask local IRQs, but for
* some reason the hardware doesn't quite think you did a proper job.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (lockdep_hardirqs_enabled()) {
struct irqtrace_events *trace = &current->irqtrace;
/*
* We have done an ON -> OFF transition:
*/
__this_cpu_write(hardirqs_enabled, 0);
trace->hardirq_disable_ip = ip;
trace->hardirq_disable_event = ++trace->irq_events;
debug_atomic_inc(hardirqs_off_events);
} else {
debug_atomic_inc(redundant_hardirqs_off);
}
}
EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
/*
* Softirqs will be enabled:
*/
void lockdep_softirqs_on(unsigned long ip)
{
struct irqtrace_events *trace = &current->irqtrace;
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
/*
* We fancy IRQs being disabled here, see softirq.c, avoids
* funny state and nesting things.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (current->softirqs_enabled) {
debug_atomic_inc(redundant_softirqs_on);
return;
}
current->lockdep_recursion++;
/*
* We'll do an OFF -> ON transition:
*/
current->softirqs_enabled = 1;
trace->softirq_enable_ip = ip;
trace->softirq_enable_event = ++trace->irq_events;
debug_atomic_inc(softirqs_on_events);
/*
* We are going to turn softirqs on, so set the
* usage bit for all held locks, if hardirqs are
* enabled too:
*/
if (lockdep_hardirqs_enabled())
mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
lockdep_recursion_finish();
}
/*
* Softirqs were disabled:
*/
void lockdep_softirqs_off(unsigned long ip)
{
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
/*
* We fancy IRQs being disabled here, see softirq.c
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (current->softirqs_enabled) {
struct irqtrace_events *trace = &current->irqtrace;
/*
* We have done an ON -> OFF transition:
*/
current->softirqs_enabled = 0;
trace->softirq_disable_ip = ip;
trace->softirq_disable_event = ++trace->irq_events;
debug_atomic_inc(softirqs_off_events);
/*
* Whoops, we wanted softirqs off, so why aren't they?
*/
DEBUG_LOCKS_WARN_ON(!softirq_count());
} else
debug_atomic_inc(redundant_softirqs_off);
}
static int
mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
{
if (!check)
goto lock_used;
/*
* If non-trylock use in a hardirq or softirq context, then
* mark the lock as used in these contexts:
*/
if (!hlock->trylock) {
if (hlock->read) {
if (lockdep_hardirq_context())
if (!mark_lock(curr, hlock,
LOCK_USED_IN_HARDIRQ_READ))
return 0;
if (curr->softirq_context)
if (!mark_lock(curr, hlock,
LOCK_USED_IN_SOFTIRQ_READ))
return 0;
} else {
if (lockdep_hardirq_context())
if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
return 0;
if (curr->softirq_context)
if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
return 0;
}
}
if (!hlock->hardirqs_off) {
if (hlock->read) {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQ_READ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQ_READ))
return 0;
} else {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQ))
return 0;
}
}
lock_used:
/* mark it as used: */
if (!mark_lock(curr, hlock, LOCK_USED))
return 0;
return 1;
}
static inline unsigned int task_irq_context(struct task_struct *task)
{
return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
}
static int separate_irq_context(struct task_struct *curr,
struct held_lock *hlock)
{
unsigned int depth = curr->lockdep_depth;
/*
* Keep track of points where we cross into an interrupt context:
*/
if (depth) {
struct held_lock *prev_hlock;
prev_hlock = curr->held_locks + depth-1;
/*
* If we cross into another context, reset the
* hash key (this also prevents the checking and the
* adding of the dependency to 'prev'):
*/
if (prev_hlock->irq_context != hlock->irq_context)
return 1;
}
return 0;
}
/*
* Mark a lock with a usage bit, and validate the state transition:
*/
static int mark_lock(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
unsigned int new_mask = 1 << new_bit, ret = 1;
if (new_bit >= LOCK_USAGE_STATES) {
DEBUG_LOCKS_WARN_ON(1);
return 0;
}
/*
* If already set then do not dirty the cacheline,
* nor do any checks:
*/
if (likely(hlock_class(this)->usage_mask & new_mask))
return 1;
if (!graph_lock())
return 0;
/*
* Make sure we didn't race:
*/
if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
graph_unlock();
return 1;
}
hlock_class(this)->usage_mask |= new_mask;
if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
return 0;
switch (new_bit) {
case LOCK_USED:
debug_atomic_dec(nr_unused_locks);
break;
default:
ret = mark_lock_irq(curr, this, new_bit);
if (!ret)
return 0;
}
graph_unlock();
/*
* We must printk outside of the graph_lock:
*/
if (ret == 2) {
printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
print_lock(this);
print_irqtrace_events(curr);
dump_stack();
}
return ret;
}
static inline short task_wait_context(struct task_struct *curr)
{
/*
* Set appropriate wait type for the context; for IRQs we have to take
* into account force_irqthread as that is implied by PREEMPT_RT.
*/
if (lockdep_hardirq_context()) {
/*
* Check if force_irqthreads will run us threaded.
*/
if (curr->hardirq_threaded || curr->irq_config)
return LD_WAIT_CONFIG;
return LD_WAIT_SPIN;
} else if (curr->softirq_context) {
/*
* Softirqs are always threaded.
*/
return LD_WAIT_CONFIG;
}
return LD_WAIT_MAX;
}
static int
print_lock_invalid_wait_context(struct task_struct *curr,
struct held_lock *hlock)
{
short curr_inner;
if (!debug_locks_off())
return 0;
if (debug_locks_silent)
return 0;
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("[ BUG: Invalid wait context ]\n");
print_kernel_ident();
pr_warn("-----------------------------\n");
pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
print_lock(hlock);
pr_warn("other info that might help us debug this:\n");
curr_inner = task_wait_context(curr);
pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
lockdep_print_held_locks(curr);
pr_warn("stack backtrace:\n");
dump_stack();
return 0;
}
/*
* Verify the wait_type context.
*
* This check validates we takes locks in the right wait-type order; that is it
* ensures that we do not take mutexes inside spinlocks and do not attempt to
* acquire spinlocks inside raw_spinlocks and the sort.
*
* The entire thing is slightly more complex because of RCU, RCU is a lock that
* can be taken from (pretty much) any context but also has constraints.
* However when taken in a stricter environment the RCU lock does not loosen
* the constraints.
*
* Therefore we must look for the strictest environment in the lock stack and
* compare that to the lock we're trying to acquire.
*/
static int check_wait_context(struct task_struct *curr, struct held_lock *next)
{
short next_inner = hlock_class(next)->wait_type_inner;
short next_outer = hlock_class(next)->wait_type_outer;
short curr_inner;
int depth;
if (!curr->lockdep_depth || !next_inner || next->trylock)
return 0;
if (!next_outer)
next_outer = next_inner;
/*
* Find start of current irq_context..
*/
for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
struct held_lock *prev = curr->held_locks + depth;
if (prev->irq_context != next->irq_context)
break;
}
depth++;
curr_inner = task_wait_context(curr);
for (; depth < curr->lockdep_depth; depth++) {
struct held_lock *prev = curr->held_locks + depth;
short prev_inner = hlock_class(prev)->wait_type_inner;
if (prev_inner) {
/*
* We can have a bigger inner than a previous one
* when outer is smaller than inner, as with RCU.
*
* Also due to trylocks.
*/
curr_inner = min(curr_inner, prev_inner);
}
}
if (next_outer > curr_inner)
return print_lock_invalid_wait_context(curr, next);
return 0;
}
#else /* CONFIG_PROVE_LOCKING */
static inline int
mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
{
return 1;
}
static inline unsigned int task_irq_context(struct task_struct *task)
{
return 0;
}
static inline int separate_irq_context(struct task_struct *curr,
struct held_lock *hlock)
{
return 0;
}
static inline int check_wait_context(struct task_struct *curr,
struct held_lock *next)
{
return 0;
}
#endif /* CONFIG_PROVE_LOCKING */
/*
* Initialize a lock instance's lock-class mapping info:
*/
void lockdep_init_map_waits(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, int subclass,
short inner, short outer)
{
int i;
for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
lock->class_cache[i] = NULL;
#ifdef CONFIG_LOCK_STAT
lock->cpu = raw_smp_processor_id();
#endif
/*
* Can't be having no nameless bastards around this place!
*/
if (DEBUG_LOCKS_WARN_ON(!name)) {
lock->name = "NULL";
return;
}
lock->name = name;
lock->wait_type_outer = outer;
lock->wait_type_inner = inner;
/*
* No key, no joy, we need to hash something.
*/
if (DEBUG_LOCKS_WARN_ON(!key))
return;
/*
* Sanity check, the lock-class key must either have been allocated
* statically or must have been registered as a dynamic key.
*/
if (!static_obj(key) && !is_dynamic_key(key)) {
if (debug_locks)
printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
DEBUG_LOCKS_WARN_ON(1);
return;
}
lock->key = key;
if (unlikely(!debug_locks))
return;
if (subclass) {
unsigned long flags;
if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
current->lockdep_recursion++;
register_lock_class(lock, subclass, 1);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
}
EXPORT_SYMBOL_GPL(lockdep_init_map_waits);
struct lock_class_key __lockdep_no_validate__;
EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
static void
print_lock_nested_lock_not_held(struct task_struct *curr,
struct held_lock *hlock,
unsigned long ip)
{
if (!debug_locks_off())
return;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("==================================\n");
pr_warn("WARNING: Nested lock was not taken\n");
print_kernel_ident();
pr_warn("----------------------------------\n");
pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
print_lock(hlock);
pr_warn("\nbut this task is not holding:\n");
pr_warn("%s\n", hlock->nest_lock->name);
pr_warn("\nstack backtrace:\n");
dump_stack();
pr_warn("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static int __lock_is_held(const struct lockdep_map *lock, int read);
/*
* This gets called for every mutex_lock*()/spin_lock*() operation.
* We maintain the dependency maps and validate the locking attempt:
*
* The callers must make sure that IRQs are disabled before calling it,
* otherwise we could get an interrupt which would want to take locks,
* which would end up in lockdep again.
*/
static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
int trylock, int read, int check, int hardirqs_off,
struct lockdep_map *nest_lock, unsigned long ip,
int references, int pin_count)
{
struct task_struct *curr = current;
struct lock_class *class = NULL;
struct held_lock *hlock;
unsigned int depth;
int chain_head = 0;
int class_idx;
u64 chain_key;
if (unlikely(!debug_locks))
return 0;
if (!prove_locking || lock->key == &__lockdep_no_validate__)
check = 0;
if (subclass < NR_LOCKDEP_CACHING_CLASSES)
class = lock->class_cache[subclass];
/*
* Not cached?
*/
if (unlikely(!class)) {
class = register_lock_class(lock, subclass, 0);
if (!class)
return 0;
}
debug_class_ops_inc(class);
if (very_verbose(class)) {
printk("\nacquire class [%px] %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
}
/*
* Add the lock to the list of currently held locks.
* (we dont increase the depth just yet, up until the
* dependency checks are done)
*/
depth = curr->lockdep_depth;
/*
* Ran out of static storage for our per-task lock stack again have we?
*/
if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
return 0;
class_idx = class - lock_classes;
if (depth) { /* we're holding locks */
hlock = curr->held_locks + depth - 1;
if (hlock->class_idx == class_idx && nest_lock) {
if (!references)
references++;
if (!hlock->references)
hlock->references++;
hlock->references += references;
/* Overflow */
if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
return 0;
return 2;
}
}
hlock = curr->held_locks + depth;
/*
* Plain impossible, we just registered it and checked it weren't no
* NULL like.. I bet this mushroom I ate was good!
*/
if (DEBUG_LOCKS_WARN_ON(!class))
return 0;
hlock->class_idx = class_idx;
hlock->acquire_ip = ip;
hlock->instance = lock;
hlock->nest_lock = nest_lock;
hlock->irq_context = task_irq_context(curr);
hlock->trylock = trylock;
hlock->read = read;
hlock->check = check;
hlock->hardirqs_off = !!hardirqs_off;
hlock->references = references;
#ifdef CONFIG_LOCK_STAT
hlock->waittime_stamp = 0;
hlock->holdtime_stamp = lockstat_clock();
#endif
hlock->pin_count = pin_count;
if (check_wait_context(curr, hlock))
return 0;
/* Initialize the lock usage bit */
if (!mark_usage(curr, hlock, check))
return 0;
/*
* Calculate the chain hash: it's the combined hash of all the
* lock keys along the dependency chain. We save the hash value
* at every step so that we can get the current hash easily
* after unlock. The chain hash is then used to cache dependency
* results.
*
* The 'key ID' is what is the most compact key value to drive
* the hash, not class->key.
*/
/*
* Whoops, we did it again.. class_idx is invalid.
*/
if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
return 0;
chain_key = curr->curr_chain_key;
if (!depth) {
/*
* How can we have a chain hash when we ain't got no keys?!
*/
if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
return 0;
chain_head = 1;
}
hlock->prev_chain_key = chain_key;
if (separate_irq_context(curr, hlock)) {
chain_key = INITIAL_CHAIN_KEY;
chain_head = 1;
}
chain_key = iterate_chain_key(chain_key, class_idx);
if (nest_lock && !__lock_is_held(nest_lock, -1)) {
print_lock_nested_lock_not_held(curr, hlock, ip);
return 0;
}
if (!debug_locks_silent) {
WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
WARN_ON_ONCE(!hlock_class(hlock)->key);
}
if (!validate_chain(curr, hlock, chain_head, chain_key))
return 0;
curr->curr_chain_key = chain_key;
curr->lockdep_depth++;
check_chain_key(curr);
#ifdef CONFIG_DEBUG_LOCKDEP
if (unlikely(!debug_locks))
return 0;
#endif
if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
debug_locks_off();
print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
printk(KERN_DEBUG "depth: %i max: %lu!\n",
curr->lockdep_depth, MAX_LOCK_DEPTH);
lockdep_print_held_locks(current);
debug_show_all_locks();
dump_stack();
return 0;
}
if (unlikely(curr->lockdep_depth > max_lockdep_depth))
max_lockdep_depth = curr->lockdep_depth;
return 1;
}
static void print_unlock_imbalance_bug(struct task_struct *curr,
struct lockdep_map *lock,
unsigned long ip)
{
if (!debug_locks_off())
return;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("=====================================\n");
pr_warn("WARNING: bad unlock balance detected!\n");
print_kernel_ident();
pr_warn("-------------------------------------\n");
pr_warn("%s/%d is trying to release lock (",
curr->comm, task_pid_nr(curr));
print_lockdep_cache(lock);
pr_cont(") at:\n");
print_ip_sym(KERN_WARNING, ip);
pr_warn("but there are no more locks to release!\n");
pr_warn("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static noinstr int match_held_lock(const struct held_lock *hlock,
const struct lockdep_map *lock)
{
if (hlock->instance == lock)
return 1;
if (hlock->references) {
const struct lock_class *class = lock->class_cache[0];
if (!class)
class = look_up_lock_class(lock, 0);
/*
* If look_up_lock_class() failed to find a class, we're trying
* to test if we hold a lock that has never yet been acquired.
* Clearly if the lock hasn't been acquired _ever_, we're not
* holding it either, so report failure.
*/
if (!class)
return 0;
/*
* References, but not a lock we're actually ref-counting?
* State got messed up, follow the sites that change ->references
* and try to make sense of it.
*/
if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
return 0;
if (hlock->class_idx == class - lock_classes)
return 1;
}
return 0;
}
/* @depth must not be zero */
static struct held_lock *find_held_lock(struct task_struct *curr,
struct lockdep_map *lock,
unsigned int depth, int *idx)
{
struct held_lock *ret, *hlock, *prev_hlock;
int i;
i = depth - 1;
hlock = curr->held_locks + i;
ret = hlock;
if (match_held_lock(hlock, lock))
goto out;
ret = NULL;
for (i--, prev_hlock = hlock--;
i >= 0;
i--, prev_hlock = hlock--) {
/*
* We must not cross into another context:
*/
if (prev_hlock->irq_context != hlock->irq_context) {
ret = NULL;
break;
}
if (match_held_lock(hlock, lock)) {
ret = hlock;
break;
}
}
out:
*idx = i;
return ret;
}
static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
int idx, unsigned int *merged)
{
struct held_lock *hlock;
int first_idx = idx;
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
switch (__lock_acquire(hlock->instance,
hlock_class(hlock)->subclass,
hlock->trylock,
hlock->read, hlock->check,
hlock->hardirqs_off,
hlock->nest_lock, hlock->acquire_ip,
hlock->references, hlock->pin_count)) {
case 0:
return 1;
case 1:
break;
case 2:
*merged += (idx == first_idx);
break;
default:
WARN_ON(1);
return 0;
}
}
return 0;
}
static int
__lock_set_class(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, unsigned int subclass,
unsigned long ip)
{
struct task_struct *curr = current;
unsigned int depth, merged = 0;
struct held_lock *hlock;
struct lock_class *class;
int i;
if (unlikely(!debug_locks))
return 0;
depth = curr->lockdep_depth;
/*
* This function is about (re)setting the class of a held lock,
* yet we're not actually holding any locks. Naughty user!
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return 0;
hlock = find_held_lock(curr, lock, depth, &i);
if (!hlock) {
print_unlock_imbalance_bug(curr, lock, ip);
return 0;
}
lockdep_init_map_waits(lock, name, key, 0,
lock->wait_type_inner,
lock->wait_type_outer);
class = register_lock_class(lock, subclass, 0);
hlock->class_idx = class - lock_classes;
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
if (reacquire_held_locks(curr, depth, i, &merged))
return 0;
/*
* I took it apart and put it back together again, except now I have
* these 'spare' parts.. where shall I put them.
*/
if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
return 0;
return 1;
}
static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
{
struct task_struct *curr = current;
unsigned int depth, merged = 0;
struct held_lock *hlock;
int i;
if (unlikely(!debug_locks))
return 0;
depth = curr->lockdep_depth;
/*
* This function is about (re)setting the class of a held lock,
* yet we're not actually holding any locks. Naughty user!
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return 0;
hlock = find_held_lock(curr, lock, depth, &i);
if (!hlock) {
print_unlock_imbalance_bug(curr, lock, ip);
return 0;
}
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
WARN(hlock->read, "downgrading a read lock");
hlock->read = 1;
hlock->acquire_ip = ip;
if (reacquire_held_locks(curr, depth, i, &merged))
return 0;
/* Merging can't happen with unchanged classes.. */
if (DEBUG_LOCKS_WARN_ON(merged))
return 0;
/*
* I took it apart and put it back together again, except now I have
* these 'spare' parts.. where shall I put them.
*/
if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
return 0;
return 1;
}
/*
* Remove the lock from the list of currently held locks - this gets
* called on mutex_unlock()/spin_unlock*() (or on a failed
* mutex_lock_interruptible()).
*/
static int
__lock_release(struct lockdep_map *lock, unsigned long ip)
{
struct task_struct *curr = current;
unsigned int depth, merged = 1;
struct held_lock *hlock;
int i;
if (unlikely(!debug_locks))
return 0;
depth = curr->lockdep_depth;
/*
* So we're all set to release this lock.. wait what lock? We don't
* own any locks, you've been drinking again?
*/
if (depth <= 0) {
print_unlock_imbalance_bug(curr, lock, ip);
return 0;
}
/*
* Check whether the lock exists in the current stack
* of held locks:
*/
hlock = find_held_lock(curr, lock, depth, &i);
if (!hlock) {
print_unlock_imbalance_bug(curr, lock, ip);
return 0;
}
if (hlock->instance == lock)
lock_release_holdtime(hlock);
WARN(hlock->pin_count, "releasing a pinned lock\n");
if (hlock->references) {
hlock->references--;
if (hlock->references) {
/*
* We had, and after removing one, still have
* references, the current lock stack is still
* valid. We're done!
*/
return 1;
}
}
/*
* We have the right lock to unlock, 'hlock' points to it.
* Now we remove it from the stack, and add back the other
* entries (if any), recalculating the hash along the way:
*/
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
/*
* The most likely case is when the unlock is on the innermost
* lock. In this case, we are done!
*/
if (i == depth-1)
return 1;
if (reacquire_held_locks(curr, depth, i + 1, &merged))
return 0;
/*
* We had N bottles of beer on the wall, we drank one, but now
* there's not N-1 bottles of beer left on the wall...
* Pouring two of the bottles together is acceptable.
*/
DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
/*
* Since reacquire_held_locks() would have called check_chain_key()
* indirectly via __lock_acquire(), we don't need to do it again
* on return.
*/
return 0;
}
static __always_inline
int __lock_is_held(const struct lockdep_map *lock, int read)
{
struct task_struct *curr = current;
int i;
for (i = 0; i < curr->lockdep_depth; i++) {
struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) {
if (read == -1 || hlock->read == read)
return 1;
return 0;
}
}
return 0;
}
static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
{
struct pin_cookie cookie = NIL_COOKIE;
struct task_struct *curr = current;
int i;
if (unlikely(!debug_locks))
return cookie;
for (i = 0; i < curr->lockdep_depth; i++) {
struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) {
/*
* Grab 16bits of randomness; this is sufficient to not
* be guessable and still allows some pin nesting in
* our u32 pin_count.
*/
cookie.val = 1 + (prandom_u32() >> 16);
hlock->pin_count += cookie.val;
return cookie;
}
}
WARN(1, "pinning an unheld lock\n");
return cookie;
}
static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
struct task_struct *curr = current;
int i;
if (unlikely(!debug_locks))
return;
for (i = 0; i < curr->lockdep_depth; i++) {
struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) {
hlock->pin_count += cookie.val;
return;
}
}
WARN(1, "pinning an unheld lock\n");
}
static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
struct task_struct *curr = current;
int i;
if (unlikely(!debug_locks))
return;
for (i = 0; i < curr->lockdep_depth; i++) {
struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) {
if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
return;
hlock->pin_count -= cookie.val;
if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
hlock->pin_count = 0;
return;
}
}
WARN(1, "unpinning an unheld lock\n");
}
/*
* Check whether we follow the irq-flags state precisely:
*/
static void check_flags(unsigned long flags)
{
#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
if (!debug_locks)
return;
if (irqs_disabled_flags(flags)) {
if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
printk("possible reason: unannotated irqs-off.\n");
}
} else {
if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
printk("possible reason: unannotated irqs-on.\n");
}
}
/*
* We dont accurately track softirq state in e.g.
* hardirq contexts (such as on 4KSTACKS), so only
* check if not in hardirq contexts:
*/
if (!hardirq_count()) {
if (softirq_count()) {
/* like the above, but with softirqs */
DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
} else {
/* lick the above, does it taste good? */
DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
}
}
if (!debug_locks)
print_irqtrace_events(current);
#endif
}
void lock_set_class(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, unsigned int subclass,
unsigned long ip)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
current->lockdep_recursion++;
check_flags(flags);
if (__lock_set_class(lock, name, key, subclass, ip))
check_chain_key(current);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_set_class);
void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
current->lockdep_recursion++;
check_flags(flags);
if (__lock_downgrade(lock, ip))
check_chain_key(current);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_downgrade);
/* NMI context !!! */
static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
{
#ifdef CONFIG_PROVE_LOCKING
struct lock_class *class = look_up_lock_class(lock, subclass);
/* if it doesn't have a class (yet), it certainly hasn't been used yet */
if (!class)
return;
if (!(class->usage_mask & LOCK_USED))
return;
hlock->class_idx = class - lock_classes;
print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
#endif
}
static bool lockdep_nmi(void)
{
if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK)
return false;
if (!in_nmi())
return false;
return true;
}
/*
* read_lock() is recursive if:
* 1. We force lockdep think this way in selftests or
* 2. The implementation is not queued read/write lock or
* 3. The locker is at an in_interrupt() context.
*/
bool read_lock_is_recursive(void)
{
return force_read_lock_recursive ||
!IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
in_interrupt();
}
EXPORT_SYMBOL_GPL(read_lock_is_recursive);
/*
* We are not always called with irqs disabled - do that here,
* and also avoid lockdep recursion:
*/
void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
int trylock, int read, int check,
struct lockdep_map *nest_lock, unsigned long ip)
{
unsigned long flags;
trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
if (unlikely(current->lockdep_recursion)) {
/* XXX allow trylock from NMI ?!? */
if (lockdep_nmi() && !trylock) {
struct held_lock hlock;
hlock.acquire_ip = ip;
hlock.instance = lock;
hlock.nest_lock = nest_lock;
hlock.irq_context = 2; // XXX
hlock.trylock = trylock;
hlock.read = read;
hlock.check = check;
hlock.hardirqs_off = true;
hlock.references = 0;
verify_lock_unused(lock, &hlock, subclass);
}
return;
}
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
__lock_acquire(lock, subclass, trylock, read, check,
irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_acquire);
void lock_release(struct lockdep_map *lock, unsigned long ip)
{
unsigned long flags;
trace_lock_release(lock, ip);
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
if (__lock_release(lock, ip))
check_chain_key(current);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_release);
noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
{
unsigned long flags;
int ret = 0;
if (unlikely(current->lockdep_recursion))
return 1; /* avoid false negative lockdep_assert_held() */
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
ret = __lock_is_held(lock, read);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
return ret;
}
EXPORT_SYMBOL_GPL(lock_is_held_type);
NOKPROBE_SYMBOL(lock_is_held_type);
struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
{
struct pin_cookie cookie = NIL_COOKIE;
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return cookie;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
cookie = __lock_pin_lock(lock);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
return cookie;
}
EXPORT_SYMBOL_GPL(lock_pin_lock);
void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
__lock_repin_lock(lock, cookie);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_repin_lock);
void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
__lock_unpin_lock(lock, cookie);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_unpin_lock);
#ifdef CONFIG_LOCK_STAT
static void print_lock_contention_bug(struct task_struct *curr,
struct lockdep_map *lock,
unsigned long ip)
{
if (!debug_locks_off())
return;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("=================================\n");
pr_warn("WARNING: bad contention detected!\n");
print_kernel_ident();
pr_warn("---------------------------------\n");
pr_warn("%s/%d is trying to contend lock (",
curr->comm, task_pid_nr(curr));
print_lockdep_cache(lock);
pr_cont(") at:\n");
print_ip_sym(KERN_WARNING, ip);
pr_warn("but there are no locks held!\n");
pr_warn("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static void
__lock_contended(struct lockdep_map *lock, unsigned long ip)
{
struct task_struct *curr = current;
struct held_lock *hlock;
struct lock_class_stats *stats;
unsigned int depth;
int i, contention_point, contending_point;
depth = curr->lockdep_depth;
/*
* Whee, we contended on this lock, except it seems we're not
* actually trying to acquire anything much at all..
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return;
hlock = find_held_lock(curr, lock, depth, &i);
if (!hlock) {
print_lock_contention_bug(curr, lock, ip);
return;
}
if (hlock->instance != lock)
return;
hlock->waittime_stamp = lockstat_clock();
contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
contending_point = lock_point(hlock_class(hlock)->contending_point,
lock->ip);
stats = get_lock_stats(hlock_class(hlock));
if (contention_point < LOCKSTAT_POINTS)
stats->contention_point[contention_point]++;
if (contending_point < LOCKSTAT_POINTS)
stats->contending_point[contending_point]++;
if (lock->cpu != smp_processor_id())
stats->bounces[bounce_contended + !!hlock->read]++;
}
static void
__lock_acquired(struct lockdep_map *lock, unsigned long ip)
{
struct task_struct *curr = current;
struct held_lock *hlock;
struct lock_class_stats *stats;
unsigned int depth;
u64 now, waittime = 0;
int i, cpu;
depth = curr->lockdep_depth;
/*
* Yay, we acquired ownership of this lock we didn't try to
* acquire, how the heck did that happen?
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return;
hlock = find_held_lock(curr, lock, depth, &i);
if (!hlock) {
print_lock_contention_bug(curr, lock, _RET_IP_);
return;
}
if (hlock->instance != lock)
return;
cpu = smp_processor_id();
if (hlock->waittime_stamp) {
now = lockstat_clock();
waittime = now - hlock->waittime_stamp;
hlock->holdtime_stamp = now;
}
stats = get_lock_stats(hlock_class(hlock));
if (waittime) {
if (hlock->read)
lock_time_inc(&stats->read_waittime, waittime);
else
lock_time_inc(&stats->write_waittime, waittime);
}
if (lock->cpu != cpu)
stats->bounces[bounce_acquired + !!hlock->read]++;
lock->cpu = cpu;
lock->ip = ip;
}
void lock_contended(struct lockdep_map *lock, unsigned long ip)
{
unsigned long flags;
trace_lock_acquired(lock, ip);
if (unlikely(!lock_stat || !debug_locks))
return;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
__lock_contended(lock, ip);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_contended);
void lock_acquired(struct lockdep_map *lock, unsigned long ip)
{
unsigned long flags;
trace_lock_contended(lock, ip);
if (unlikely(!lock_stat || !debug_locks))
return;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
__lock_acquired(lock, ip);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_acquired);
#endif
/*
* Used by the testsuite, sanitize the validator state
* after a simulated failure:
*/
void lockdep_reset(void)
{
unsigned long flags;
int i;
raw_local_irq_save(flags);
lockdep_init_task(current);
memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
nr_hardirq_chains = 0;
nr_softirq_chains = 0;
nr_process_chains = 0;
debug_locks = 1;
for (i = 0; i < CHAINHASH_SIZE; i++)
INIT_HLIST_HEAD(chainhash_table + i);
raw_local_irq_restore(flags);
}
/* Remove a class from a lock chain. Must be called with the graph lock held. */
static void remove_class_from_lock_chain(struct pending_free *pf,
struct lock_chain *chain,
struct lock_class *class)
{
#ifdef CONFIG_PROVE_LOCKING
int i;
for (i = chain->base; i < chain->base + chain->depth; i++) {
if (chain_hlocks[i] != class - lock_classes)
continue;
/*
* Each lock class occurs at most once in a lock chain so once
* we found a match we can break out of this loop.
*/
goto free_lock_chain;
}
/* Since the chain has not been modified, return. */
return;
free_lock_chain:
free_chain_hlocks(chain->base, chain->depth);
/* Overwrite the chain key for concurrent RCU readers. */
WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
dec_chains(chain->irq_context);
/*
* Note: calling hlist_del_rcu() from inside a
* hlist_for_each_entry_rcu() loop is safe.
*/
hlist_del_rcu(&chain->entry);
__set_bit(chain - lock_chains, pf->lock_chains_being_freed);
nr_zapped_lock_chains++;
#endif
}
/* Must be called with the graph lock held. */
static void remove_class_from_lock_chains(struct pending_free *pf,
struct lock_class *class)
{
struct lock_chain *chain;
struct hlist_head *head;
int i;
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
head = chainhash_table + i;
hlist_for_each_entry_rcu(chain, head, entry) {
remove_class_from_lock_chain(pf, chain, class);
}
}
}
/*
* Remove all references to a lock class. The caller must hold the graph lock.
*/
static void zap_class(struct pending_free *pf, struct lock_class *class)
{
struct lock_list *entry;
int i;
WARN_ON_ONCE(!class->key);
/*
* Remove all dependencies this lock is
* involved in:
*/
for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
entry = list_entries + i;
if (entry->class != class && entry->links_to != class)
continue;
__clear_bit(i, list_entries_in_use);
nr_list_entries--;
list_del_rcu(&entry->entry);
}
if (list_empty(&class->locks_after) &&
list_empty(&class->locks_before)) {
list_move_tail(&class->lock_entry, &pf->zapped);
hlist_del_rcu(&class->hash_entry);
WRITE_ONCE(class->key, NULL);
WRITE_ONCE(class->name, NULL);
nr_lock_classes--;
__clear_bit(class - lock_classes, lock_classes_in_use);
} else {
WARN_ONCE(true, "%s() failed for class %s\n", __func__,
class->name);
}
remove_class_from_lock_chains(pf, class);
nr_zapped_classes++;
}
static void reinit_class(struct lock_class *class)
{
void *const p = class;
const unsigned int offset = offsetof(struct lock_class, key);
WARN_ON_ONCE(!class->lock_entry.next);
WARN_ON_ONCE(!list_empty(&class->locks_after));
WARN_ON_ONCE(!list_empty(&class->locks_before));
memset(p + offset, 0, sizeof(*class) - offset);
WARN_ON_ONCE(!class->lock_entry.next);
WARN_ON_ONCE(!list_empty(&class->locks_after));
WARN_ON_ONCE(!list_empty(&class->locks_before));
}
static inline int within(const void *addr, void *start, unsigned long size)
{
return addr >= start && addr < start + size;
}
static bool inside_selftest(void)
{
return current == lockdep_selftest_task_struct;
}
/* The caller must hold the graph lock. */
static struct pending_free *get_pending_free(void)
{
return delayed_free.pf + delayed_free.index;
}
static void free_zapped_rcu(struct rcu_head *cb);
/*
* Schedule an RCU callback if no RCU callback is pending. Must be called with
* the graph lock held.
*/
static void call_rcu_zapped(struct pending_free *pf)
{
WARN_ON_ONCE(inside_selftest());
if (list_empty(&pf->zapped))
return;
if (delayed_free.scheduled)
return;
delayed_free.scheduled = true;
WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
delayed_free.index ^= 1;
call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
}
/* The caller must hold the graph lock. May be called from RCU context. */
static void __free_zapped_classes(struct pending_free *pf)
{
struct lock_class *class;
check_data_structures();
list_for_each_entry(class, &pf->zapped, lock_entry)
reinit_class(class);
list_splice_init(&pf->zapped, &free_lock_classes);
#ifdef CONFIG_PROVE_LOCKING
bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
#endif
}
static void free_zapped_rcu(struct rcu_head *ch)
{
struct pending_free *pf;
unsigned long flags;
if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
return;
raw_local_irq_save(flags);
lockdep_lock();
/* closed head */
pf = delayed_free.pf + (delayed_free.index ^ 1);
__free_zapped_classes(pf);
delayed_free.scheduled = false;
/*
* If there's anything on the open list, close and start a new callback.
*/
call_rcu_zapped(delayed_free.pf + delayed_free.index);
lockdep_unlock();
raw_local_irq_restore(flags);
}
/*
* Remove all lock classes from the class hash table and from the
* all_lock_classes list whose key or name is in the address range [start,
* start + size). Move these lock classes to the zapped_classes list. Must
* be called with the graph lock held.
*/
static void __lockdep_free_key_range(struct pending_free *pf, void *start,
unsigned long size)
{
struct lock_class *class;
struct hlist_head *head;
int i;
/* Unhash all classes that were created by a module. */
for (i = 0; i < CLASSHASH_SIZE; i++) {
head = classhash_table + i;
hlist_for_each_entry_rcu(class, head, hash_entry) {
if (!within(class->key, start, size) &&
!within(class->name, start, size))
continue;
zap_class(pf, class);
}
}
}
/*
* Used in module.c to remove lock classes from memory that is going to be
* freed; and possibly re-used by other modules.
*
* We will have had one synchronize_rcu() before getting here, so we're
* guaranteed nobody will look up these exact classes -- they're properly dead
* but still allocated.
*/
static void lockdep_free_key_range_reg(void *start, unsigned long size)
{
struct pending_free *pf;
unsigned long flags;
init_data_structures_once();
raw_local_irq_save(flags);
lockdep_lock();
pf = get_pending_free();
__lockdep_free_key_range(pf, start, size);
call_rcu_zapped(pf);
lockdep_unlock();
raw_local_irq_restore(flags);
/*
* Wait for any possible iterators from look_up_lock_class() to pass
* before continuing to free the memory they refer to.
*/
synchronize_rcu();
}
/*
* Free all lockdep keys in the range [start, start+size). Does not sleep.
* Ignores debug_locks. Must only be used by the lockdep selftests.
*/
static void lockdep_free_key_range_imm(void *start, unsigned long size)
{
struct pending_free *pf = delayed_free.pf;
unsigned long flags;
init_data_structures_once();
raw_local_irq_save(flags);
lockdep_lock();
__lockdep_free_key_range(pf, start, size);
__free_zapped_classes(pf);
lockdep_unlock();
raw_local_irq_restore(flags);
}
void lockdep_free_key_range(void *start, unsigned long size)
{
init_data_structures_once();
if (inside_selftest())
lockdep_free_key_range_imm(start, size);
else
lockdep_free_key_range_reg(start, size);
}
/*
* Check whether any element of the @lock->class_cache[] array refers to a
* registered lock class. The caller must hold either the graph lock or the
* RCU read lock.
*/
static bool lock_class_cache_is_registered(struct lockdep_map *lock)
{
struct lock_class *class;
struct hlist_head *head;
int i, j;
for (i = 0; i < CLASSHASH_SIZE; i++) {
head = classhash_table + i;
hlist_for_each_entry_rcu(class, head, hash_entry) {
for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
if (lock->class_cache[j] == class)
return true;
}
}
return false;
}
/* The caller must hold the graph lock. Does not sleep. */
static void __lockdep_reset_lock(struct pending_free *pf,
struct lockdep_map *lock)
{
struct lock_class *class;
int j;
/*
* Remove all classes this lock might have:
*/
for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
/*
* If the class exists we look it up and zap it:
*/
class = look_up_lock_class(lock, j);
if (class)
zap_class(pf, class);
}
/*
* Debug check: in the end all mapped classes should
* be gone.
*/
if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
debug_locks_off();
}
/*
* Remove all information lockdep has about a lock if debug_locks == 1. Free
* released data structures from RCU context.
*/
static void lockdep_reset_lock_reg(struct lockdep_map *lock)
{
struct pending_free *pf;
unsigned long flags;
int locked;
raw_local_irq_save(flags);
locked = graph_lock();
if (!locked)
goto out_irq;
pf = get_pending_free();
__lockdep_reset_lock(pf, lock);
call_rcu_zapped(pf);
graph_unlock();
out_irq:
raw_local_irq_restore(flags);
}
/*
* Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
* lockdep selftests.
*/
static void lockdep_reset_lock_imm(struct lockdep_map *lock)
{
struct pending_free *pf = delayed_free.pf;
unsigned long flags;
raw_local_irq_save(flags);
lockdep_lock();
__lockdep_reset_lock(pf, lock);
__free_zapped_classes(pf);
lockdep_unlock();
raw_local_irq_restore(flags);
}
void lockdep_reset_lock(struct lockdep_map *lock)
{
init_data_structures_once();
if (inside_selftest())
lockdep_reset_lock_imm(lock);
else
lockdep_reset_lock_reg(lock);
}
/* Unregister a dynamically allocated key. */
void lockdep_unregister_key(struct lock_class_key *key)
{
struct hlist_head *hash_head = keyhashentry(key);
struct lock_class_key *k;
struct pending_free *pf;
unsigned long flags;
bool found = false;
might_sleep();
if (WARN_ON_ONCE(static_obj(key)))
return;
raw_local_irq_save(flags);
if (!graph_lock())
goto out_irq;
pf = get_pending_free();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (k == key) {
hlist_del_rcu(&k->hash_entry);
found = true;
break;
}
}
WARN_ON_ONCE(!found);
__lockdep_free_key_range(pf, key, 1);
call_rcu_zapped(pf);
graph_unlock();
out_irq:
raw_local_irq_restore(flags);
/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
synchronize_rcu();
}
EXPORT_SYMBOL_GPL(lockdep_unregister_key);
void __init lockdep_init(void)
{
printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
printk(" memory used by lock dependency info: %zu kB\n",
(sizeof(lock_classes) +
sizeof(lock_classes_in_use) +
sizeof(classhash_table) +
sizeof(list_entries) +
sizeof(list_entries_in_use) +
sizeof(chainhash_table) +
sizeof(delayed_free)
#ifdef CONFIG_PROVE_LOCKING
+ sizeof(lock_cq)
+ sizeof(lock_chains)
+ sizeof(lock_chains_in_use)
+ sizeof(chain_hlocks)
#endif
) / 1024
);
#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
printk(" memory used for stack traces: %zu kB\n",
(sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
);
#endif
printk(" per task-struct memory footprint: %zu bytes\n",
sizeof(((struct task_struct *)NULL)->held_locks));
}
static void
print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
const void *mem_to, struct held_lock *hlock)
{
if (!debug_locks_off())
return;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("=========================\n");
pr_warn("WARNING: held lock freed!\n");
print_kernel_ident();
pr_warn("-------------------------\n");
pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
print_lock(hlock);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
static inline int not_in_range(const void* mem_from, unsigned long mem_len,
const void* lock_from, unsigned long lock_len)
{
return lock_from + lock_len <= mem_from ||
mem_from + mem_len <= lock_from;
}
/*
* Called when kernel memory is freed (or unmapped), or if a lock
* is destroyed or reinitialized - this code checks whether there is
* any held lock in the memory range of <from> to <to>:
*/
void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
{
struct task_struct *curr = current;
struct held_lock *hlock;
unsigned long flags;
int i;
if (unlikely(!debug_locks))
return;
raw_local_irq_save(flags);
for (i = 0; i < curr->lockdep_depth; i++) {
hlock = curr->held_locks + i;
if (not_in_range(mem_from, mem_len, hlock->instance,
sizeof(*hlock->instance)))
continue;
print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
break;
}
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
static void print_held_locks_bug(void)
{
if (!debug_locks_off())
return;
if (debug_locks_silent)
return;
pr_warn("\n");
pr_warn("====================================\n");
pr_warn("WARNING: %s/%d still has locks held!\n",
current->comm, task_pid_nr(current));
print_kernel_ident();
pr_warn("------------------------------------\n");
lockdep_print_held_locks(current);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
void debug_check_no_locks_held(void)
{
if (unlikely(current->lockdep_depth > 0))
print_held_locks_bug();
}
EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
#ifdef __KERNEL__
void debug_show_all_locks(void)
{
struct task_struct *g, *p;
if (unlikely(!debug_locks)) {
pr_warn("INFO: lockdep is turned off.\n");
return;
}
pr_warn("\nShowing all locks held in the system:\n");
rcu_read_lock();
for_each_process_thread(g, p) {
if (!p->lockdep_depth)
continue;
lockdep_print_held_locks(p);
touch_nmi_watchdog();
touch_all_softlockup_watchdogs();
}
rcu_read_unlock();
pr_warn("\n");
pr_warn("=============================================\n\n");
}
EXPORT_SYMBOL_GPL(debug_show_all_locks);
#endif
/*
* Careful: only use this function if you are sure that
* the task cannot run in parallel!
*/
void debug_show_held_locks(struct task_struct *task)
{
if (unlikely(!debug_locks)) {
printk("INFO: lockdep is turned off.\n");
return;
}
lockdep_print_held_locks(task);
}
EXPORT_SYMBOL_GPL(debug_show_held_locks);
asmlinkage __visible void lockdep_sys_exit(void)
{
struct task_struct *curr = current;
if (unlikely(curr->lockdep_depth)) {
if (!debug_locks_off())
return;
pr_warn("\n");
pr_warn("================================================\n");
pr_warn("WARNING: lock held when returning to user space!\n");
print_kernel_ident();
pr_warn("------------------------------------------------\n");
pr_warn("%s/%d is leaving the kernel with locks still held!\n",
curr->comm, curr->pid);
lockdep_print_held_locks(curr);
}
/*
* The lock history for each syscall should be independent. So wipe the
* slate clean on return to userspace.
*/
lockdep_invariant_state(false);
}
void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
{
struct task_struct *curr = current;
/* Note: the following can be executed concurrently, so be careful. */
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("WARNING: suspicious RCU usage\n");
print_kernel_ident();
pr_warn("-----------------------------\n");
pr_warn("%s:%d %s!\n", file, line, s);
pr_warn("\nother info that might help us debug this:\n\n");
pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
!rcu_lockdep_current_cpu_online()
? "RCU used illegally from offline CPU!\n"
: "",
rcu_scheduler_active, debug_locks);
/*
* If a CPU is in the RCU-free window in idle (ie: in the section
* between rcu_idle_enter() and rcu_idle_exit(), then RCU
* considers that CPU to be in an "extended quiescent state",
* which means that RCU will be completely ignoring that CPU.
* Therefore, rcu_read_lock() and friends have absolutely no
* effect on a CPU running in that state. In other words, even if
* such an RCU-idle CPU has called rcu_read_lock(), RCU might well
* delete data structures out from under it. RCU really has no
* choice here: we need to keep an RCU-free window in idle where
* the CPU may possibly enter into low power mode. This way we can
* notice an extended quiescent state to other CPUs that started a grace
* period. Otherwise we would delay any grace period as long as we run
* in the idle task.
*
* So complain bitterly if someone does call rcu_read_lock(),
* rcu_read_lock_bh() and so on from extended quiescent states.
*/
if (!rcu_is_watching())
pr_warn("RCU used illegally from extended quiescent state!\n");
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
}
EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
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