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locking/rwsem: Check for operations on an uninitialized rwsem

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Currently rwsems is the only locking primitive that lacks this
debug feature. Add it under CONFIG_DEBUG_RWSEMS and do the magic
checking in the locking fastpath (trylock) operation such that
we cover all cases. The unlocking part is pretty straightforward.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: mingo@kernel.org
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lkml.kernel.org/r/20190729044735.9632-1-dave@stgolabs.net
This commit is contained in:
Davidlohr Bueso 2019-07-28 21:47:35 -07:00 committed by Peter Zijlstra
parent 91d2a812df
commit fce45cd411
2 changed files with 28 additions and 4 deletions
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10
include/linux/rwsem.h
View File

@ -45,6 +45,9 @@ struct rw_semaphore {
#endif
raw_spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_RWSEMS
void *magic;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
@ -73,6 +76,12 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
#ifdef CONFIG_DEBUG_RWSEMS
# define __DEBUG_RWSEM_INITIALIZER(lockname) , .magic = &lockname
#else
# define __DEBUG_RWSEM_INITIALIZER(lockname)
#endif
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED
#else
@ -85,6 +94,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
.wait_list = LIST_HEAD_INIT((name).wait_list), \
.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
__RWSEM_OPT_INIT(name) \
__DEBUG_RWSEM_INITIALIZER(name) \
__RWSEM_DEP_MAP_INIT(name) }
#define DECLARE_RWSEM(name) \

22
kernel/locking/rwsem.c
View File

@ -105,8 +105,9 @@
#ifdef CONFIG_DEBUG_RWSEMS
# define DEBUG_RWSEMS_WARN_ON(c, sem) do { \
if (!debug_locks_silent && \
WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\
WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, magic = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\
#c, atomic_long_read(&(sem)->count), \
(unsigned long) sem->magic, \
atomic_long_read(&(sem)->owner), (long)current, \
list_empty(&(sem)->wait_list) ? "" : "not ")) \
debug_locks_off(); \
@ -329,6 +330,9 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
*/
debug_check_no_locks_freed((void *)sem, sizeof(*sem));
lockdep_init_map(&sem->dep_map, name, key, 0);
#endif
#ifdef CONFIG_DEBUG_RWSEMS
sem->magic = sem;
#endif
atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
raw_spin_lock_init(&sem->wait_lock);
@ -1358,11 +1362,14 @@ static inline int __down_read_killable(struct rw_semaphore *sem)
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
long tmp;
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
/*
* Optimize for the case when the rwsem is not locked at all.
*/
long tmp = RWSEM_UNLOCKED_VALUE;
tmp = RWSEM_UNLOCKED_VALUE;
do {
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
tmp + RWSEM_READER_BIAS)) {
@ -1403,8 +1410,11 @@ static inline int __down_write_killable(struct rw_semaphore *sem)
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
long tmp = RWSEM_UNLOCKED_VALUE;
long tmp;
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
tmp = RWSEM_UNLOCKED_VALUE;
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
@ -1420,7 +1430,9 @@ inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
rwsem_clear_reader_owned(sem);
tmp = atomic_long_add_return_release(-RWSEM_READER_BIAS, &sem->count);
DEBUG_RWSEMS_WARN_ON(tmp < 0, sem);
@ -1438,12 +1450,14 @@ static inline void __up_write(struct rw_semaphore *sem)
{
long tmp;
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
/*
* sem->owner may differ from current if the ownership is transferred
* to an anonymous writer by setting the RWSEM_NONSPINNABLE bits.
*/
DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) &&
!rwsem_test_oflags(sem, RWSEM_NONSPINNABLE), sem);
rwsem_clear_owner(sem);
tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count);
if (unlikely(tmp & RWSEM_FLAG_WAITERS))