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jump_label: Reorder hotplug lock and jump_label_lock

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The conversion of the hotplug locking to a percpu rwsem unearthed lock
ordering issues all over the place.

The jump_label code has two issues:

 1) Nested get_online_cpus() invocations

 2) Ordering problems vs. the cpus rwsem and the jump_label_mutex

To cure these, the following lock order has been established;

   cpus_rwsem -> jump_label_lock -> text_mutex

Even if not all architectures need protection against CPU hotplug, taking
cpus_rwsem before jump_label_lock is now mandatory in code pathes which
actually modify code and therefor need text_mutex protection.

Move the get_online_cpus() invocations into the core jump label code and
establish the proper lock order where required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "David S. Miller" <davem@davemloft.net>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Link: http://lkml.kernel.org/r/20170524081549.025830817@linutronix.de
This commit is contained in:
Thomas Gleixner 2017-05-24 10:15:35 +02:00
parent a63fbed776
commit f2545b2d4c
5 changed files with 14 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/mips/kernel/jump_label.c
View File

@ -58,7 +58,6 @@ void arch_jump_label_transform(struct jump_entry *e,
insn.word = 0; /* nop */
}
get_online_cpus();
mutex_lock(&text_mutex);
if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
insn_p->halfword[0] = insn.word >> 16;
@ -70,7 +69,6 @@ void arch_jump_label_transform(struct jump_entry *e,
(unsigned long)insn_p + sizeof(*insn_p));
mutex_unlock(&text_mutex);
put_online_cpus();
}
#endif /* HAVE_JUMP_LABEL */

2
arch/sparc/kernel/jump_label.c
View File

@ -41,12 +41,10 @@ void arch_jump_label_transform(struct jump_entry *entry,
val = 0x01000000;
}
get_online_cpus();
mutex_lock(&text_mutex);
*insn = val;
flushi(insn);
mutex_unlock(&text_mutex);
put_online_cpus();
}
#endif

2
arch/tile/kernel/jump_label.c
View File

@ -45,14 +45,12 @@ static void __jump_label_transform(struct jump_entry *e,
void arch_jump_label_transform(struct jump_entry *e,
enum jump_label_type type)
{
get_online_cpus();
mutex_lock(&text_mutex);
__jump_label_transform(e, type);
flush_icache_range(e->code, e->code + sizeof(tilegx_bundle_bits));
mutex_unlock(&text_mutex);
put_online_cpus();
}
__init_or_module void arch_jump_label_transform_static(struct jump_entry *e,

2
arch/x86/kernel/jump_label.c
View File

@ -105,11 +105,9 @@ static void __jump_label_transform(struct jump_entry *entry,
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
get_online_cpus();
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, NULL, 0);
mutex_unlock(&text_mutex);
put_online_cpus();
}
static enum {

20
kernel/jump_label.c
View File

@ -15,6 +15,7 @@
#include <linux/static_key.h>
#include <linux/jump_label_ratelimit.h>
#include <linux/bug.h>
#include <linux/cpu.h>
#ifdef HAVE_JUMP_LABEL
@ -124,6 +125,7 @@ void static_key_slow_inc(struct static_key *key)
return;
}
cpus_read_lock();
jump_label_lock();
if (atomic_read(&key->enabled) == 0) {
atomic_set(&key->enabled, -1);
@ -133,12 +135,14 @@ void static_key_slow_inc(struct static_key *key)
atomic_inc(&key->enabled);
}
jump_label_unlock();
cpus_read_unlock();
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);
static void __static_key_slow_dec(struct static_key *key,
unsigned long rate_limit, struct delayed_work *work)
{
cpus_read_lock();
/*
* The negative count check is valid even when a negative
* key->enabled is in use by static_key_slow_inc(); a
@ -149,6 +153,7 @@ static void __static_key_slow_dec(struct static_key *key,
if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
WARN(atomic_read(&key->enabled) < 0,
"jump label: negative count!\n");
cpus_read_unlock();
return;
}
@ -159,6 +164,7 @@ static void __static_key_slow_dec(struct static_key *key,
jump_label_update(key);
}
jump_label_unlock();
cpus_read_unlock();
}
static void jump_label_update_timeout(struct work_struct *work)
@ -334,6 +340,7 @@ void __init jump_label_init(void)
if (static_key_initialized)
return;
cpus_read_lock();
jump_label_lock();
jump_label_sort_entries(iter_start, iter_stop);
@ -353,6 +360,7 @@ void __init jump_label_init(void)
}
static_key_initialized = true;
jump_label_unlock();
cpus_read_unlock();
}
#ifdef CONFIG_MODULES
@ -590,28 +598,28 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,
struct module *mod = data;
int ret = 0;
cpus_read_lock();
jump_label_lock();
switch (val) {
case MODULE_STATE_COMING:
jump_label_lock();
ret = jump_label_add_module(mod);
if (ret) {
WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
jump_label_del_module(mod);
}
jump_label_unlock();
break;
case MODULE_STATE_GOING:
jump_label_lock();
jump_label_del_module(mod);
jump_label_unlock();
break;
case MODULE_STATE_LIVE:
jump_label_lock();
jump_label_invalidate_module_init(mod);
jump_label_unlock();
break;
}
jump_label_unlock();
cpus_read_unlock();
return notifier_from_errno(ret);
}