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

[Peter Zijlstra]

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
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