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charset="UTF-8" On-demand memory shrinking (perf_session__shrink(), dsos__shrink(), symbols__shrink()) can be triggered from OOM recovery inside allocation wrappers while the current thread already holds a rw_semaphore (such as symbols->lock, dsos->lock, or machines->lock). Non-blocking trylock primitives are needed so shrinking paths can safely skip any locked container without deadlocking. Add non-blocking down_read_trylock() and down_write_trylock() wrappers around pthread_rwlock_tryrdlock() / pthread_rwlock_trywrlock() and pthread_mutex_trylock() along with SHARED_TRYLOCK_FUNCTION and EXCLUSIVE_TRYLOCK_FUNCTION thread-safety annotations. Signed-off-by: Ian Rogers --- tools/perf/util/mutex.h | 3 +++ tools/perf/util/rwsem.c | 20 ++++++++++++++++++++ tools/perf/util/rwsem.h | 11 +++++++++++ 3 files changed, 34 insertions(+) diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h index 5de1065ea2b9..de7dd6d8326c 100644 --- a/tools/perf/util/mutex.h +++ b/tools/perf/util/mutex.h @@ -57,6 +57,8 @@ /* Documents functions that try to acquire a lock, and return success or failure. */ #define EXCLUSIVE_TRYLOCK_FUNCTION(...) \ __attribute__((exclusive_trylock_function(__VA_ARGS__))) +#define SHARED_TRYLOCK_FUNCTION(...) \ + __attribute__((shared_trylock_function(__VA_ARGS__))) /* Documents a function that expects a mutex to be held prior to entry. */ #define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__))) @@ -78,6 +80,7 @@ #define SHARED_LOCK_FUNCTION(...) #define UNLOCK_FUNCTION(...) #define EXCLUSIVE_TRYLOCK_FUNCTION(...) +#define SHARED_TRYLOCK_FUNCTION(...) #define EXCLUSIVE_LOCKS_REQUIRED(...) #define SHARED_LOCKS_REQUIRED(...) #define NO_THREAD_SAFETY_ANALYSIS diff --git a/tools/perf/util/rwsem.c b/tools/perf/util/rwsem.c index 1d15c0e3732b..9548a3b44f16 100644 --- a/tools/perf/util/rwsem.c +++ b/tools/perf/util/rwsem.c @@ -36,6 +36,16 @@ int down_read(struct rw_semaphore *sem) #endif } +bool down_read_trylock(struct rw_semaphore *sem) + NO_THREAD_SAFETY_ANALYSIS +{ +#if RWS_ERRORCHECK + return mutex_trylock(&sem->mtx); +#else + return pthread_rwlock_tryrdlock(&sem->lock) == 0; +#endif +} + int up_read(struct rw_semaphore *sem) NO_THREAD_SAFETY_ANALYSIS { @@ -58,6 +68,16 @@ int down_write(struct rw_semaphore *sem) #endif } +bool down_write_trylock(struct rw_semaphore *sem) + NO_THREAD_SAFETY_ANALYSIS +{ +#if RWS_ERRORCHECK + return mutex_trylock(&sem->mtx); +#else + return pthread_rwlock_trywrlock(&sem->lock) == 0; +#endif +} + int up_write(struct rw_semaphore *sem) NO_THREAD_SAFETY_ANALYSIS { diff --git a/tools/perf/util/rwsem.h b/tools/perf/util/rwsem.h index b102d8143181..53c45990d9c9 100644 --- a/tools/perf/util/rwsem.h +++ b/tools/perf/util/rwsem.h @@ -22,9 +22,20 @@ int init_rwsem(struct rw_semaphore *sem); int exit_rwsem(struct rw_semaphore *sem); int down_read(struct rw_semaphore *sem) SHARED_LOCK_FUNCTION(sem); +/* + * Tries to acquire a shared read lock without blocking. Per POSIX + * pthread_rwlock_tryrdlock(), succeeds when no writer holds or blocks on @sem + * (including when the calling thread already holds a read lock on @sem). + */ +bool down_read_trylock(struct rw_semaphore *sem) SHARED_TRYLOCK_FUNCTION(true, sem); int up_read(struct rw_semaphore *sem) UNLOCK_FUNCTION(sem); int down_write(struct rw_semaphore *sem) EXCLUSIVE_LOCK_FUNCTION(sem); +/* + * Tries to acquire an exclusive write lock without blocking. Returns false if + * any thread (including the calling thread) holds a read or write lock on @sem. + */ +bool down_write_trylock(struct rw_semaphore *sem) EXCLUSIVE_TRYLOCK_FUNCTION(true, sem); int up_write(struct rw_semaphore *sem) UNLOCK_FUNCTION(sem); #endif /* _PERF_RWSEM_H */ -- 2.56.1.703.gf848ed807c-goog