From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761279AbXGCT4k (ORCPT ); Tue, 3 Jul 2007 15:56:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757744AbXGCT4d (ORCPT ); Tue, 3 Jul 2007 15:56:33 -0400 Received: from www.osadl.org ([213.239.205.134]:52505 "EHLO mail.tglx.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757663AbXGCT4d (ORCPT ); Tue, 3 Jul 2007 15:56:33 -0400 Subject: Re: [PATCH] NTP: remove clock_was_set() call to prevent deadlock From: Thomas Gleixner To: Linus Torvalds Cc: LKML , Dave Jones , Andrew Morton , john stultz , Ingo Molnar , Stable Team , "Fortier,Vincent [Montreal]" In-Reply-To: <1183485920.3291.28.camel@chaos> References: <1183485920.3291.28.camel@chaos> Content-Type: text/plain Date: Tue, 03 Jul 2007 21:56:30 +0200 Message-Id: <1183492590.3291.39.camel@chaos> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 (2.10.1-4.fc7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2007-07-03 at 20:05 +0200, Thomas Gleixner wrote: > The clock_was_set() call in seconds_overflow() which happens only when > leap seconds are inserted / deleted is wrong in two aspects: > > 1. it results in a call to on_each_cpu() with interrupts disabled > 2. it is potential deadlock source vs. call_lock in smp_call_function() > > The only possible side effect of the removal might be, that an absolute > CLOCK_REALTIME timer fires 1 second too late, in the rare case of leap > second deletion and an absolute CLOCK_REALTIME timer which expires in > the affected time frame. It will never fire too early. > > This was probably observed by the reporter of a June 30th -> July 1st > hang: http://lkml.org/lkml/2007/7/3/ Ooops, missed the full reference: http://lkml.org/lkml/2007/7/3/103 tglx