From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755427Ab2IMJ2J (ORCPT ); Thu, 13 Sep 2012 05:28:09 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:56732 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753892Ab2IMJ2F (ORCPT ); Thu, 13 Sep 2012 05:28:05 -0400 Message-ID: <5051A71C.1070802@linux.vnet.ibm.com> Date: Thu, 13 Sep 2012 17:27:56 +0800 From: Michael Wang User-Agent: Mozilla/5.0 (X11; Linux i686; rv:15.0) Gecko/20120827 Thunderbird/15.0 MIME-Version: 1.0 To: LKML CC: mingo@redhat.com, Peter Zijlstra Subject: Re: [PATCH] sched: unify the check on atomic sleeping in __might_sleep() and schedule_bug() References: <503446AA.2020004@linux.vnet.ibm.com> <504412F7.1020200@linux.vnet.ibm.com> In-Reply-To: <504412F7.1020200@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12091309-9574-0000-0000-000004654360 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/2012 10:16 AM, Michael Wang wrote: > On 08/22/2012 10:40 AM, Michael Wang wrote: >> From: Michael Wang >> >> Fengguang Wu has reported the bug: >> >> [ 0.043953] BUG: scheduling while atomic: swapper/0/1/0x10000002 >> [ 0.044017] no locks held by swapper/0/1. >> [ 0.044692] Pid: 1, comm: swapper/0 Not tainted 3.6.0-rc1-00420-gb7aebb9 #34 >> [ 0.045861] Call Trace: >> [ 0.048071] [] __schedule_bug+0x5e/0x70 >> [ 0.048890] [] __schedule+0x91/0xb10 >> [ 0.049660] [] ? vsnprintf+0x33a/0x450 >> [ 0.050444] [] ? lg_local_lock+0x6/0x70 >> [ 0.051256] [] ? wait_for_xmitr+0x31/0x90 >> [ 0.052019] [] ? do_raw_spin_unlock+0xa5/0xf0 >> [ 0.052903] [] ? _raw_spin_unlock+0x22/0x30 >> [ 0.053759] [] ? up+0x1b/0x70 >> [ 0.054421] [] __cond_resched+0x1b/0x30 >> [ 0.055228] [] _cond_resched+0x45/0x50 >> [ 0.056020] [] mutex_lock_nested+0x28/0x370 >> [ 0.056884] [] ? console_unlock+0x3a2/0x4e0 >> [ 0.057741] [] __irq_alloc_descs+0x39/0x1c0 >> [ 0.058589] [] io_apic_setup_irq_pin+0x2c/0x310 >> [ 0.060042] [] setup_IO_APIC+0x101/0x744 >> [ 0.060878] [] ? clear_IO_APIC+0x31/0x50 >> [ 0.061695] [] native_smp_prepare_cpus+0x538/0x680 >> [ 0.062644] [] ? do_one_initcall+0x12c/0x12c >> [ 0.063517] [] ? do_one_initcall+0x12c/0x12c >> [ 0.064016] [] kernel_init+0x4b/0x17f >> [ 0.064790] [] ? do_one_initcall+0x12c/0x12c >> [ 0.065660] [] kernel_thread_helper+0x6/0x10 >> >> It was caused by that: >> >> native_smp_prepare_cpus() >> preempt_disable() //preempt_count++ >> mutex_lock() //in __irq_alloc_descs >> __might_sleep() //system is booting, avoid check >> might_resched() >> __schedule() >> preempt_disable() //preempt_count++ >> schedule_bug() //preempt_count > 1, report bug >> >> The __might_sleep() avoid check on atomic sleeping until the system booted >> while the schedule_bug() doesn't, it's the reason for the bug. >> >> This patch will add one additional check in schedule_bug() to avoid check >> until the system booted, so the check on atomic sleeping will be unified. > > Could I get some comments on this patch? Oh, I just realised I'm using the wrong address... So could I get some comments on the patch? Regards, Michael Wang > > Regards, > Michael Wang >> >> Signed-off-by: Michael Wang >> Tested-by: Fengguang Wu >> --- >> kernel/sched/core.c | 3 ++- >> 1 files changed, 2 insertions(+), 1 deletions(-) >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 4376c9f..3396c33 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -3321,7 +3321,8 @@ static inline void schedule_debug(struct task_struct *prev) >> * schedule() atomically, we ignore that path for now. >> * Otherwise, whine if we are scheduling when we should not be. >> */ >> - if (unlikely(in_atomic_preempt_off() && !prev->exit_state)) >> + if (unlikely(in_atomic_preempt_off() && !prev->exit_state >> + && system_state == SYSTEM_RUNNING)) >> __schedule_bug(prev); >> rcu_sleep_check(); >> >> >