Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning

Peter Zijlstra
2009-01-09T18:16:48Z

On Fri, 2009-01-09 at 11:44 -0500, Steven Rostedt wrote:

> When we get to the schedule() it then needs to be a:
>
> preempt_enable_no_resched();
> schedule();

On that note:

Index: linux-2.6/kernel/mutex.c
===================================================================
--- linux-2.6.orig/kernel/mutex.c
+++ linux-2.6/kernel/mutex.c
@@ -220,7 +220,9 @@ __mutex_lock_common(struct mutex *lock,
__set_task_state(task, state);

/* didnt get the lock, go to sleep: */
+ preempt_disable();
spin_unlock_mutex(&lock->wait_lock, flags);
+ preempt_enable_no_resched();
schedule();
spin_lock_mutex(&lock->wait_lock, flags);
}

actually improves mutex performance on PREEMPT=y