From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761483AbYEOQtQ (ORCPT ); Thu, 15 May 2008 12:49:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753871AbYEOQtB (ORCPT ); Thu, 15 May 2008 12:49:01 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:40303 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753657AbYEOQtB (ORCPT ); Thu, 15 May 2008 12:49:01 -0400 Subject: Re: [Bug 10648] CONFIG_PRINTK_TIME broken on git HEAD ? From: Peter Zijlstra To: bugme-daemon@bugzilla.kernel.org Cc: Ingo Molnar , linux-kernel In-Reply-To: <20080515162703.D4970108060@picon.linux-foundation.org> References: <20080515162703.D4970108060@picon.linux-foundation.org> Content-Type: text/plain Date: Thu, 15 May 2008 18:48:46 +0200 Message-Id: <1210870126.6524.16.camel@lappy.programming.kicks-ass.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Subject: sched: fix sched_clock_cpu() From: Peter Zijlstra Make sched_clock_cpu() return 0 before it has been initialised and avoid corrupting its state due to doing so. Signed-off-by: Peter Zijlstra --- kernel/sched_clock.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) Index: linux-2.6/kernel/sched_clock.c =================================================================== --- linux-2.6.orig/kernel/sched_clock.c 2008-05-13 18:40:35.000000000 +0200 +++ linux-2.6/kernel/sched_clock.c 2008-05-13 18:42:05.000000000 +0200 @@ -60,22 +60,26 @@ return &per_cpu(sched_clock_data, cpu); } +static __read_mostly int sched_clock_running; + void sched_clock_init(void) { u64 ktime_now = ktime_to_ns(ktime_get()); - u64 now = 0; + unsigned long now_jiffies = jiffies; int cpu; for_each_possible_cpu(cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; - scd->prev_jiffies = jiffies; - scd->prev_raw = now; - scd->tick_raw = now; + scd->prev_jiffies = now_jiffies; + scd->prev_raw = 0; + scd->tick_raw = 0; scd->tick_gtod = ktime_now; scd->clock = ktime_now; } + + sched_clock_running = 1; } /* @@ -137,6 +141,9 @@ struct sched_clock_data *scd = cpu_sdc(cpu); u64 now, clock; + if (unlikely(!sched_clock_running)) + return 0ull; + /* * Normally this is not called in NMI context - but if it is, * trying to do any locking here is totally lethal. @@ -182,6 +189,9 @@ struct sched_clock_data *scd = this_scd(); u64 now, now_gtod; + if (unlikely(!sched_clock_running)) + return; + WARN_ON_ONCE(!irqs_disabled()); now = sched_clock();