From a7d2c573ae7fad1b2c877d1a1342fa5bb0d6478c Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Tue, 7 May 2013 06:45:56 -0700 Subject: [PATCH] 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 Reviewed-by: Peter Hurley Acked-by: Davidlohr Bueso Acked-by: Rik van Riel Signed-off-by: Linus Torvalds --- lib/rwsem.c | 10 ++++++++-- 1 file 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); } -- 2.20.1