Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932799AbXBVH4f (ORCPT ); Thu, 22 Feb 2007 02:56:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932803AbXBVH4e (ORCPT ); Thu, 22 Feb 2007 02:56:34 -0500 Received: from www.osadl.org ([213.239.205.134]:50531 "EHLO mail.tglx.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932799AbXBVH4e (ORCPT ); Thu, 22 Feb 2007 02:56:34 -0500 Subject: Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Ingo Molnar Cc: Andrew Morton , john stultz , Roman Zippel , Mike Galbraith , balducci@units.it, LKML , Greg KH In-Reply-To: <20070222074624.GA9800@elte.hu> References: <20070221104747.3cb0da32.akpm@linux-foundation.org> <1172104409.25076.165.camel@localhost.localdomain> <20070222074624.GA9800@elte.hu> Content-Type: text/plain Date: Thu, 22 Feb 2007 09:01:39 +0100 Message-Id: <1172131299.25076.168.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 979 Lines: 28 On Thu, 2007-02-22 at 08:46 +0100, Ingo Molnar wrote: > * Thomas Gleixner wrote: > > > The problem is that the p->last_ran value is not updated after a > > context switch. So a subsequent call to current_sched_time() > > calculates with a stale p->last_ran value, i.e. accounts the full > > time, which the task was scheduled away. > > > > Signed-off-by: Thomas Gleixner > > > sched_info_switch(prev, next); > > if (likely(prev != next)) { > > - next->timestamp = now; > > + next->timestamp = next->last_ran = now; > > ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be > unaffected. Yes, was introduced in 2.6.20 and definitely should hit the stable tree. tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/