diff options
| -rw-r--r-- | kernel/locking/lock_events_list.h | 1 | ||||
| -rw-r--r-- | kernel/locking/rwsem.c | 28 |
2 files changed, 29 insertions, 0 deletions
diff --git a/kernel/locking/lock_events_list.h b/kernel/locking/lock_events_list.h index 239039d0ce21..270a0d351932 100644 --- a/kernel/locking/lock_events_list.h +++ b/kernel/locking/lock_events_list.h @@ -63,6 +63,7 @@ LOCK_EVENT(rwsem_opt_nospin) /* # of disabled optspins */ LOCK_EVENT(rwsem_opt_norspin) /* # of disabled reader-only optspins */ LOCK_EVENT(rwsem_opt_rlock2) /* # of opt-acquired 2ndary read locks */ LOCK_EVENT(rwsem_rlock) /* # of read locks acquired */ +LOCK_EVENT(rwsem_rlock_steal) /* # of read locks by lock stealing */ LOCK_EVENT(rwsem_rlock_fast) /* # of fast read locks acquired */ LOCK_EVENT(rwsem_rlock_fail) /* # of failed read lock acquisitions */ LOCK_EVENT(rwsem_rlock_handoff) /* # of read lock handoffs */ diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index c055f4b28b23..ba5e239d08e7 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -976,6 +976,12 @@ static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem, } return false; } + +static inline bool rwsem_no_spinners(struct rw_semaphore *sem) +{ + return !osq_is_locked(&sem->osq); +} + #else static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable) @@ -996,6 +1002,11 @@ static inline bool rwsem_reader_phase_trylock(struct rw_semaphore *sem, return false; } +static inline bool rwsem_no_spinners(sem) +{ + return false; +} + static inline int rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable) { @@ -1027,6 +1038,22 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state) goto queue; /* + * Reader optimistic lock stealing + * + * We can take the read lock directly without doing + * rwsem_optimistic_spin() if the conditions are right. + * Also wake up other readers if it is the first reader. + */ + if (!(count & (RWSEM_WRITER_LOCKED | RWSEM_FLAG_HANDOFF)) && + rwsem_no_spinners(sem)) { + rwsem_set_reader_owned(sem); + lockevent_inc(rwsem_rlock_steal); + if (rcnt == 1) + goto wake_readers; + return sem; + } + + /* * Save the current read-owner of rwsem, if available, and the * reader nonspinnable bit. */ @@ -1048,6 +1075,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state) * Wake up other readers in the wait list if the front * waiter is a reader. */ +wake_readers: if ((atomic_long_read(&sem->count) & RWSEM_FLAG_WAITERS)) { raw_spin_lock_irq(&sem->wait_lock); if (!list_empty(&sem->wait_list)) |