Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752549AbYKRLFw (ORCPT ); Tue, 18 Nov 2008 06:05:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751902AbYKRLFo (ORCPT ); Tue, 18 Nov 2008 06:05:44 -0500 Received: from styx.suse.cz ([82.119.242.94]:54232 "EHLO mail.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751879AbYKRLFn (ORCPT ); Tue, 18 Nov 2008 06:05:43 -0500 Date: Tue, 18 Nov 2008 12:05:42 +0100 From: Michal Hocko To: Ingo Molnar Cc: Luis Henriques , linux-kernel@vger.kernel.org Subject: Re: [BUG] using smp_processor_id() in preemptible Message-ID: <20081118110541.GA5336@dhcp35.suse.cz> References: <20081115233050.GA13439@hades> <20081116071059.GA19646@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081116071059.GA19646@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4441 Lines: 116 On Sun 16-11-08 08:10:59, Ingo Molnar wrote: > > * Luis Henriques wrote: > > > Hi Ingo, > > > > while running latencytop, got the following: > > > > [ 775.663239] BUG: using smp_processor_id() in preemptible [00000000] code: latencytop/6585 > > [ 775.663303] caller is native_sched_clock+0x3a/0x80 > > [ 775.663314] Pid: 6585, comm: latencytop Tainted: G W 2.6.28-rc4-00355-g9c7c354 #1 > > [ 775.663322] Call Trace: > > [ 775.663343] [] debug_smp_processor_id+0xe4/0xf0 > > [ 775.663356] [] native_sched_clock+0x3a/0x80 > > [ 775.663368] [] sched_clock+0x9/0x10 > > [ 775.663381] [] proc_sched_show_task+0x8bd/0x10e0 > > [ 775.663395] [] sched_show+0x3e/0x80 > > [ 775.663408] [] seq_read+0xdb/0x350 > > [ 775.663421] [] ? security_file_permission+0x16/0x20 > > [ 775.663435] [] vfs_read+0xc8/0x170 > > [ 775.663447] [] sys_read+0x55/0x90 > > [ 775.663460] [] system_call_fastpath+0x16/0x1b > > ... > > > > I am running 2.6.28-rc4-00355-g9c7c354 and, after taking a look at > > the code, it looks like the problem is in commit > > 7cbaef9c83e58bbd4bdd534b09052b6c5ec457d5, where native_sched_clock > > is modified to use __cycles_2_ns instead of cycles_2_ns. > > indeed. Does the fix below work for you? Yes, it fixes problem on my end... (reported at http://www.gossamer-threads.com/lists/linux/kernel/997205). > > Thanks, > > Ingo > > --------------> > From 29d7b90c15035741d15421b36000509212b3e135 Mon Sep 17 00:00:00 2001 > From: Ingo Molnar > Date: Sun, 16 Nov 2008 08:07:15 +0100 > Subject: [PATCH] sched: fix kernel warning on /proc/sched_debug access > > Luis Henriques reported that with CONFIG_PREEMPT=y + CONFIG_PREEMPT_DEBUG=y + > CONFIG_SCHED_DEBUG=y + CONFIG_LATENCYTOP=y enabled, the following warning > triggers when using latencytop: > > > [ 775.663239] BUG: using smp_processor_id() in preemptible [00000000] code: latencytop/6585 > > [ 775.663303] caller is native_sched_clock+0x3a/0x80 > > [ 775.663314] Pid: 6585, comm: latencytop Tainted: G W 2.6.28-rc4-00355-g9c7c354 #1 > > [ 775.663322] Call Trace: > > [ 775.663343] [] debug_smp_processor_id+0xe4/0xf0 > > [ 775.663356] [] native_sched_clock+0x3a/0x80 > > [ 775.663368] [] sched_clock+0x9/0x10 > > [ 775.663381] [] proc_sched_show_task+0x8bd/0x10e0 > > [ 775.663395] [] sched_show+0x3e/0x80 > > [ 775.663408] [] seq_read+0xdb/0x350 > > [ 775.663421] [] ? security_file_permission+0x16/0x20 > > [ 775.663435] [] vfs_read+0xc8/0x170 > > [ 775.663447] [] sys_read+0x55/0x90 > > [ 775.663460] [] system_call_fastpath+0x16/0x1b > > ... > > This breakage was caused by me via: > > 7cbaef9: sched: optimize sched_clock() a bit > > Change the calls to cpu_clock(). > > Reported-by: Luis Henriques Tested-by: Michal Hocko > --- > kernel/sched_debug.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c > index 48ecc51..26ed8e3 100644 > --- a/kernel/sched_debug.c > +++ b/kernel/sched_debug.c > @@ -423,10 +423,11 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) > #undef __P > > { > + unsigned int this_cpu = raw_smp_processor_id(); > u64 t0, t1; > > - t0 = sched_clock(); > - t1 = sched_clock(); > + t0 = cpu_clock(this_cpu); > + t1 = cpu_clock(this_cpu); > SEQ_printf(m, "%-35s:%21Ld\n", > "clock-delta", (long long)(t1-t0)); > } > > -- > 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/ -- Michal Hocko L3 team SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/