From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756443AbZBIXv3 (ORCPT ); Mon, 9 Feb 2009 18:51:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752500AbZBIXvT (ORCPT ); Mon, 9 Feb 2009 18:51:19 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:57370 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753215AbZBIXvS (ORCPT ); Mon, 9 Feb 2009 18:51:18 -0500 Date: Tue, 10 Feb 2009 00:50:58 +0100 From: Ingo Molnar To: Hugh Dickins Cc: Lennert Buytenhek , Rusty Russell , Rafael Wysocki , linux-kernel@vger.kernel.org Subject: Re: /proc/profile broken on UP machines in 2.6.29-rc3 Message-ID: <20090209235058.GC862@elte.hu> References: <20090209145058.GY13433@xi.wantstofly.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Hugh Dickins wrote: > On Mon, 9 Feb 2009, Lennert Buytenhek wrote: > > > I'm about 130k emails behind on my linux-kernel@ subscription, so I'm > > not entirely sure whether this has been reported, but it seems that > > profiling is broken on !CONFIG_SMP builds in 2.6.29-rc3. > > Yes, and CONFIG_SMP builds, and 2.6.29-rc4. > > > It appears that since this commit: > > > > commit c309b917cab55799ea489d7b5f1b77025d9f8462 > > Author: Rusty Russell > > Date: Thu Jan 1 10:12:27 2009 +1030 > > > > cpumask: convert kernel/profile.c > > > > there's no longer anything that sets any bits in prof_cpu_mask on > > UP systems at all (the default was to assign CPU_MASK_ALL, and > > profile_cpu_callback() which clears/sets bits at run time is only > > built and registered on SMP builds), so the cpumask_test_cpu() > > test in profile_tick() always fails, and no samples are ever counted. > > I guess if you cpu down and up, or suspend and resume, that will get > aux cpus profiling in the SMP case, but basically SMP is as broken as > UP. I noticed yesterday, took a look earlier today, here's the patch > which gets it working for me: > > > [PATCH] fix broken profiling regression > > Commit c309b917cab55799ea489d7b5f1b77025d9f8462 "cpumask: convert > kernel/profile.c" broke profiling. prof_cpu_mask was previously > initialized to CPU_MASK_ALL, but left uninitialized in that commit. > We need to copy cpu_possible_mask (cpu_online_mask is not enough). > > Signed-off-by: Hugh Dickins > --- > > kernel/profile.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- 2.6.29-rc4/kernel/profile.c 2009-01-11 01:33:38.000000000 +0000 > +++ linux/kernel/profile.c 2009-02-09 15:23:34.000000000 +0000 > @@ -114,12 +114,15 @@ int __ref profile_init(void) > if (!slab_is_available()) { > prof_buffer = alloc_bootmem(buffer_bytes); > alloc_bootmem_cpumask_var(&prof_cpu_mask); > + cpumask_copy(prof_cpu_mask, cpu_possible_mask); > return 0; > } > > if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL)) > return -ENOMEM; > > + cpumask_copy(prof_cpu_mask, cpu_possible_mask); > + > prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL); > if (prof_buffer) > return 0; indeed. Applied to tip/tracing/urgent, thanks Hugh! Ingo