Commit a7d2c573 authored by Michel Lespinasse's avatar Michel Lespinasse Committed by Linus Torvalds

rwsem: avoid taking wait_lock in rwsem_down_write_failed

In rwsem_down_write_failed(), if there are active locks after we wake up
(i.e.  the lock got stolen from us), skip taking the wait_lock and go
back to sleep immediately.
Signed-off-by: default avatarMichel Lespinasse <walken@google.com>
Reviewed-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Acked-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5ede972d
...@@ -214,8 +214,8 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) ...@@ -214,8 +214,8 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED); sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
/* wait until we successfully acquire the lock */ /* wait until we successfully acquire the lock */
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
while (true) { while (true) {
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
/* Try acquiring the write lock. */ /* Try acquiring the write lock. */
count = RWSEM_ACTIVE_WRITE_BIAS; count = RWSEM_ACTIVE_WRITE_BIAS;
...@@ -226,7 +226,13 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) ...@@ -226,7 +226,13 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
break; break;
raw_spin_unlock_irq(&sem->wait_lock); raw_spin_unlock_irq(&sem->wait_lock);
schedule();
/* Block until there are no active lockers. */
do {
schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
} while (sem->count & RWSEM_ACTIVE_MASK);
raw_spin_lock_irq(&sem->wait_lock); raw_spin_lock_irq(&sem->wait_lock);
} }
......
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