diff options
| -rw-r--r-- | kernel/locking/rwsem.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h index 8f43ba234787..a699f4048ba1 100644 --- a/kernel/locking/rwsem.h +++ b/kernel/locking/rwsem.h @@ -16,14 +16,21 @@ #define RWSEM_READER_OWNED ((struct task_struct *)1UL) #ifdef CONFIG_RWSEM_SPIN_ON_OWNER +/* + * All writes to owner are protected by WRITE_ONCE() to make sure that + * store tearing can't happen as optimistic spinners may read and use + * the owner value concurrently without lock. Read from owner, however, + * may not need READ_ONCE() as long as the pointer value is only used + * for comparison and isn't being dereferenced. + */ static inline void rwsem_set_owner(struct rw_semaphore *sem) { - sem->owner = current; + WRITE_ONCE(sem->owner, current); } static inline void rwsem_clear_owner(struct rw_semaphore *sem) { - sem->owner = NULL; + WRITE_ONCE(sem->owner, NULL); } static inline void rwsem_set_reader_owned(struct rw_semaphore *sem) @@ -34,7 +41,7 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem) * to minimize cacheline contention. */ if (sem->owner != RWSEM_READER_OWNED) - sem->owner = RWSEM_READER_OWNED; + WRITE_ONCE(sem->owner, RWSEM_READER_OWNED); } static inline bool rwsem_owner_is_writer(struct task_struct *owner) |