Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932229Ab1FQN45 (ORCPT ); Fri, 17 Jun 2011 09:56:57 -0400 Received: from s15228384.onlinehome-server.info ([87.106.30.177]:51715 "EHLO mail.x86-64.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753834Ab1FQN44 (ORCPT ); Fri, 17 Jun 2011 09:56:56 -0400 Date: Fri, 17 Jun 2011 15:56:34 +0200 From: Borislav Petkov To: Hidetoshi Seto Cc: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "Luck, Tony" Subject: Re: [PATCH 1/8] x86, mce: stop calling del_timer_sync() from interrupt Message-ID: <20110617135634.GF18054@aftab> References: <4DFB1242.90404@jp.fujitsu.com> <4DFB1304.10604@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DFB1304.10604@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4162 Lines: 132 On Fri, Jun 17, 2011 at 04:40:36AM -0400, Hidetoshi Seto wrote: > Function del_timer_sync() has WARN_ON(in_irq()) in it because > calling it from interrupt context can cause deadlock if it > interrupts the target timer running. No need to explain the del_timer_sync() code here - just say that it's not allowed to call it from an IRQ context. > In MCE code, del_timer_sync() is used with on_each_cpu() in > some parts for sysfs files: ... for the following sysfs files: > bank*, check_interval, cmci_disabled and ignore_ce. > > However use of on_each_cpu() results in calling the function > passed as the argument in the interrupt context. It means you > can see a flood of warnings from del_timer_sync() by a simple > file access, for example: > > echo 300 > /sys/devices/system/machinecheck/machinecheck0/check_interval Good. > > Fortunately these MCE specific files are rare-used and AFAIK rarely used > only few MCE geeks experience this warning on write. MCE geeks ??? I wonder who those are :-) > To remove the warning (for my happy hacking), move timer deletion > outside of the interrupt context ;-) > > v2: update patch description > > Signed-off-by: Hidetoshi Seto > --- > arch/x86/kernel/cpu/mcheck/mce.c | 22 ++++++++++++++++------ > 1 files changed, 16 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c > index 08363b0..42fc8d2 100644 > --- a/arch/x86/kernel/cpu/mcheck/mce.c > +++ b/arch/x86/kernel/cpu/mcheck/mce.c > @@ -1140,6 +1140,17 @@ static void mce_start_timer(unsigned long data) > add_timer_on(t, smp_processor_id()); > } > > +/* Must not be called from interrupt where del_timer_sync() can deadlock */ > +static void mce_timer_delete_all(void) > +{ > + int cpu; > + > + for_each_online_cpu(cpu) { > + if (mce_available(&per_cpu(cpu_info, cpu))) > + del_timer_sync(&per_cpu(mce_timer, cpu)); > + } > +} You're adding the mce_available(..) check just to remove it in the next patch. Since all those sysfs nodes are behind such a check, there's no need for it here too. > static void mce_do_trigger(struct work_struct *work) > { > call_usermodehelper(mce_helper, mce_helper_argv, NULL, UMH_NO_WAIT); > @@ -1750,7 +1761,6 @@ static struct syscore_ops mce_syscore_ops = { > > static void mce_cpu_restart(void *data) > { > - del_timer_sync(&__get_cpu_var(mce_timer)); > if (!mce_available(__this_cpu_ptr(&cpu_info))) > return; > __mcheck_cpu_init_generic(); > @@ -1760,16 +1770,15 @@ static void mce_cpu_restart(void *data) > /* Reinit MCEs after user configuration changes */ > static void mce_restart(void) > { > + mce_timer_delete_all(); > on_each_cpu(mce_cpu_restart, NULL, 1); > } > > /* Toggle features for corrected errors */ > -static void mce_disable_ce(void *all) > +static void mce_disable_cmci(void *data) > { > if (!mce_available(__this_cpu_ptr(&cpu_info))) > return; > - if (all) > - del_timer_sync(&__get_cpu_var(mce_timer)); > cmci_clear(); > } > > @@ -1852,7 +1861,8 @@ static ssize_t set_ignore_ce(struct sys_device *s, > if (mce_ignore_ce ^ !!new) { > if (new) { > /* disable ce features */ > - on_each_cpu(mce_disable_ce, (void *)1, 1); > + mce_timer_delete_all(); > + on_each_cpu(mce_disable_cmci, NULL, 1); > mce_ignore_ce = 1; > } else { > /* enable ce features */ > @@ -1875,7 +1885,7 @@ static ssize_t set_cmci_disabled(struct sys_device *s, > if (mce_cmci_disabled ^ !!new) { > if (new) { > /* disable cmci */ > - on_each_cpu(mce_disable_ce, NULL, 1); > + on_each_cpu(mce_disable_cmci, NULL, 1); > mce_cmci_disabled = 1; > } else { > /* enable cmci */ > -- > 1.7.1 -- Regards/Gruss, Boris. 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