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locking: Add rwsem_assert_held() and rwsem_assert_held_write() 

Modelled after lockdep_assert_held() and lockdep_assert_held_write(),
but are always active, even when lockdep is disabled.  Of course, they
don't test that _this_ thread is the owner, but it's sufficient to catch
many bugs and doesn't incur the same performance penalty as lockdep.

Acked-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-02-19 15:41:11 +00:00 committed by Chandan Babu R
parent 49c379d3a7
commit f70405afc9
2 changed files with 48 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/rwbase_rt.h
View File

@ -26,12 +26,17 @@ struct rwbase_rt {
} while (0)
static __always_inline bool rw_base_is_locked(struct rwbase_rt *rwb)
static __always_inline bool rw_base_is_locked(const struct rwbase_rt *rwb)
{
return atomic_read(&rwb->readers) != READER_BIAS;
}
static __always_inline bool rw_base_is_contended(struct rwbase_rt *rwb)
static inline void rw_base_assert_held_write(const struct rwbase_rt *rwb)
{
WARN_ON(atomic_read(&rwb->readers) != WRITER_BIAS);
}
static __always_inline bool rw_base_is_contended(const struct rwbase_rt *rwb)
{
return atomic_read(&rwb->readers) > 0;
}

46
include/linux/rwsem.h
View File

@ -66,14 +66,24 @@ struct rw_semaphore {
#endif
};
/* In all implementations count != 0 means locked */
#define RWSEM_UNLOCKED_VALUE 0UL
#define RWSEM_WRITER_LOCKED (1UL << 0)
#define __RWSEM_COUNT_INIT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
return atomic_long_read(&sem->count) != 0;
return atomic_long_read(&sem->count) != RWSEM_UNLOCKED_VALUE;
}
#define RWSEM_UNLOCKED_VALUE 0L
#define __RWSEM_COUNT_INIT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem)
{
WARN_ON(atomic_long_read(&sem->count) == RWSEM_UNLOCKED_VALUE);
}
static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
{
WARN_ON(!(atomic_long_read(&sem->count) & RWSEM_WRITER_LOCKED));
}
/* Common initializer macros and functions */
@ -152,11 +162,21 @@ do { \
__init_rwsem((sem), #sem, &__key); \
} while (0)
static __always_inline int rwsem_is_locked(struct rw_semaphore *sem)
static __always_inline int rwsem_is_locked(const struct rw_semaphore *sem)
{
return rw_base_is_locked(&sem->rwbase);
}
static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem)
{
WARN_ON(!rwsem_is_locked(sem));
}
static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
{
rw_base_assert_held_write(sem);
}
static __always_inline int rwsem_is_contended(struct rw_semaphore *sem)
{
return rw_base_is_contended(&sem->rwbase);
@ -169,6 +189,22 @@ static __always_inline int rwsem_is_contended(struct rw_semaphore *sem)
* the RT specific variant.
*/
static inline void rwsem_assert_held(const struct rw_semaphore *sem)
{
if (IS_ENABLED(CONFIG_LOCKDEP))
lockdep_assert_held(sem);
else
rwsem_assert_held_nolockdep(sem);
}
static inline void rwsem_assert_held_write(const struct rw_semaphore *sem)
{
if (IS_ENABLED(CONFIG_LOCKDEP))
lockdep_assert_held_write(sem);
else
rwsem_assert_held_write_nolockdep(sem);
}
/*
* lock for reading
*/