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From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: <linux-kernel@vger.kernel.org>
Subject: bug in sched.c:activate_task()
Date: Mon, 4 Oct 2004 19:16:39 -0700	[thread overview]
Message-ID: <200410050216.i952Gb620657@unix-os.sc.intel.com> (raw)

Update p->timestamp to "now" in activate_task() doesn't look right
to me at all.  p->timestamp records last time it was running on a
cpu.  activate_task shouldn't update that variable when it queues
a task on the runqueue.

This bug (and combined with others) triggers improper load balancing.

Patch against linux-2.6.9-rc3.  Didn't diff it against 2.6.9-rc3-mm2
because mm tree has so many change in sched.c.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>


--- linux-2.6.9-rc3/kernel/sched.c.orig	2004-10-04 19:11:21.000000000 -0700
+++ linux-2.6.9-rc3/kernel/sched.c	2004-10-04 19:11:35.000000000 -0700
@@ -888,7 +888,6 @@ static void activate_task(task_t *p, run
 			p->activated = 1;
 		}
 	}
-	p->timestamp = now;

 	__activate_task(p, rq);
 }



             reply	other threads:[~2004-10-05  2:16 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-10-05  2:16 Chen, Kenneth W [this message]
2004-10-05  2:34 ` bug in sched.c:activate_task() Con Kolivas
2004-10-05  3:14   ` Nick Piggin
2004-10-05  4:45     ` Con Kolivas
2004-10-05  5:05   ` Peter Williams
2004-10-05  6:10 ` Nick Piggin
2004-10-05  6:31 ` Ingo Molnar
2004-10-05  6:36   ` Con Kolivas
2004-10-05  6:54     ` Ingo Molnar
2004-10-05  6:59       ` Con Kolivas
2004-10-05  7:08         ` Nick Piggin
2004-10-05  7:09         ` Ingo Molnar
2004-10-05 17:30           ` Chen, Kenneth W
2004-10-05 17:25       ` Chen, Kenneth W
2004-10-05  6:57     ` Nick Piggin
2004-10-05  8:19 ` Ingo Molnar
2004-10-05 17:44   ` Chen, Kenneth W
  -- strict thread matches above, loose matches on Subject: below --
2004-10-05 22:46 Chen, Kenneth W

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