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

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

[Ingo Molnar]

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

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

[Ingo Molnar]

[-- Attachment #1: Type: text/plain, Size: 513 bytes --]


(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 --]
[-- Type: text/plain, Size: 516 bytes --]

--- 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();