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authorMichel Lespinasse <walken@google.com>2013-05-07 06:45:56 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-07 07:20:16 -0700
commita7d2c573ae7fad1b2c877d1a1342fa5bb0d6478c (patch)
tree1494f94f71a299d32a3584565a538e5ffdef1163 /lib
parent5ede972df1cd9294c82e9515949fd2103be81d7b (diff)
downloadlinux-linaro-stable-a7d2c573ae7fad1b2c877d1a1342fa5bb0d6478c.tar.gz
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: Michel Lespinasse <walken@google.com> Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/rwsem.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/lib/rwsem.c b/lib/rwsem.c
index 64c2dc007be2..edf3d9ca670e 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -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);
/* wait until we successfully acquire the lock */
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
while (true) {
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
/* Try acquiring the write lock. */
count = RWSEM_ACTIVE_WRITE_BIAS;
@@ -226,7 +226,13 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
break;
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);
}