Re: [sched patch] more sync wakeups, 2.6.5-rc3-mm1

[Ingo Molnar <mingo@elte.hu>]

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(patch attached now.)

* Ingo Molnar <mingo@elte.hu> wrote:

> the attached patch extends sync wakeups to the process sys_exit() path
> too: the chldwait wakeup can be done sync, since we know that the
> process is going to exit (and thus deschedule).
> 
> the most visible effect of this change is strace's behavior on SMP
> systems: it now stays on a single CPU, together with the traced child. 
> (previously it would run in parallel to the child, bouncing around
> madly.)
> 
> compiled & tested.
> 
> 	Ingo

[-- Attachment #2: sched-more-sync-wakeups.patch --]
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--- linux/kernel/signal.c.orig	
+++ linux/kernel/signal.c	
@@ -1386,12 +1386,12 @@ static inline void __wake_up_parent(stru
 	 * Fortunately this is not necessary for thread groups:
 	 */
 	if (p->tgid == tsk->tgid) {
-		wake_up_interruptible(&tsk->wait_chldexit);
+		wake_up_interruptible_sync(&tsk->wait_chldexit);
 		return;
 	}
 
 	do {
-		wake_up_interruptible(&tsk->wait_chldexit);
+		wake_up_interruptible_sync(&tsk->wait_chldexit);
 		tsk = next_thread(tsk);
 		if (tsk->signal != parent->signal)
 			BUG();