[PATCH, RFC] protect call to set_tsk_need_resched() by the rq-lock

[Michael Buesch <mbuesch@freenet.de>]

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Hi,

The two attached patches (one against vanilla kernel and one
against ck patchset) moves the rq-lock a few lines up in
scheduler_tick() to also protect set_tsk_need_resched().

Is that neccessary?
If yes, please apply.

-- 
Regards Michael Buesch  [ http://www.tuxsoft.de.vu ]



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Index: linux-2.5/kernel/sched.c
===================================================================
RCS file: /home/mb/develop/linux/rsync/linux-2.5/kernel/sched.c,v
retrieving revision 1.382
diff -u -p -r1.382 sched.c
--- linux-2.5/kernel/sched.c	19 Nov 2004 22:51:35 -0000	1.382
+++ linux-2.5/kernel/sched.c	6 Dec 2004 22:32:09 -0000
@@ -2318,12 +2318,12 @@ void scheduler_tick(int user_ticks, int 
 		cpustat->user += user_ticks;
 	cpustat->system += sys_ticks;
 
+	spin_lock(&rq->lock);
 	/* Task might have expired already, but not scheduled off yet */
 	if (p->array != rq->active) {
 		set_tsk_need_resched(p);
-		goto out;
+		goto out_unlock;
 	}
-	spin_lock(&rq->lock);
 	/*
 	 * The task was running during this tick - update the
 	 * time slice counter. Note: we do not update a thread's

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--- linux-2.6.10-rc3-ck1-nozeroram/kernel/sched.c.orig	2004-12-05 01:55:08.000000000 +0100
+++ linux-2.6.10-rc3-ck1-nozeroram/kernel/sched.c	2004-12-06 23:27:41.000000000 +0100
@@ -2147,18 +2147,18 @@
 		cpustat->user += user_ticks;
 	cpustat->system += sys_ticks;
 
+	spin_lock(&rq->lock);
 	/* Task might have expired already, but not scheduled off yet */
 	if (unlikely(!task_queued(p))) {
 		set_tsk_need_resched(p);
-		goto out;
+		goto out_unlock;
 	}
 	/*
 	 * SCHED_FIFO tasks never run out of timeslice.
 	 */
 	if (unlikely(p->policy == SCHED_FIFO))
-		goto out;
+		goto out_unlock;
 
-	spin_lock(&rq->lock);
 	debit = ns_diff(rq->timestamp_last_tick, p->timestamp);
 	p->ns_debit += debit;
 	if (p->ns_debit < NSJIFFY)

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