From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754708Ab0KBSTm (ORCPT ); Tue, 2 Nov 2010 14:19:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65150 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753541Ab0KBSTi (ORCPT ); Tue, 2 Nov 2010 14:19:38 -0400 From: Don Zickus To: Ingo Molnar Cc: Peter Zijlstra , Dongdong Deng , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Don Zickus Subject: [PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at the same time on SMP Date: Tue, 2 Nov 2010 14:16:58 -0400 Message-Id: <1288721818-10851-1-git-send-email-dzickus@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dongdong Deng The spin_lock_debug/rcu_cpu_stall detector uses trigger_all_cpu_backtrace() to dump cpu backtrace. Therefore it is possible that trigger_all_cpu_backtrace() could be called at the same time on different CPUs, which triggers and 'unknown reason NMI' warning. The following case illustrates the problem: CPU1 CPU2 ... CPU N trigger_all_cpu_backtrace() set "backtrace_mask" to cpu mask | generate NMI interrupts generate NMI interrupts ... \ | / \ | / The "backtrace_mask" will be cleaned by the first NMI interrupt at nmi_watchdog_tick(), then the following NMI interrupts generated by other cpus's arch_trigger_all_cpu_backtrace() will be took as unknown reason NMI interrupts. This patch uses a lock to avoid the problem, and stop the arch_trigger_all_cpu_backtrace() calling to avoid dumping double cpu backtrace info when there is already a trigger_all_cpu_backtrace() in progress. Signed-off-by: Dongdong Deng Reviewed-by: Bruce Ashfield CC: Thomas Gleixner CC: Ingo Molnar CC: "H. Peter Anvin" CC: x86@kernel.org CC: linux-kernel@vger.kernel.org Signed-off-by: Don Zickus --- arch/x86/kernel/apic/hw_nmi.c | 14 ++++++++++++++ arch/x86/kernel/apic/nmi.c | 14 ++++++++++++++ 2 files changed, 28 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index cefd694..3aea0a5 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -29,6 +29,16 @@ u64 hw_nmi_get_sample_period(void) void arch_trigger_all_cpu_backtrace(void) { int i; + static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED; + unsigned long flags; + + local_irq_save(flags); + if (!arch_spin_trylock(&lock)) + /* + * If there is already a trigger_all_cpu_backtrace() + * in progress, don't output double cpu dump infos. + */ + goto out_restore_irq; cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); @@ -41,6 +51,10 @@ void arch_trigger_all_cpu_backtrace(void) break; mdelay(1); } + + arch_spin_unlock(&lock); +out_restore_irq: + local_irq_restore(flags); } static int __kprobes diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c index a43f71c..5fa8a13 100644 --- a/arch/x86/kernel/apic/nmi.c +++ b/arch/x86/kernel/apic/nmi.c @@ -552,6 +552,16 @@ int do_nmi_callback(struct pt_regs *regs, int cpu) void arch_trigger_all_cpu_backtrace(void) { int i; + static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED; + unsigned long flags; + + local_irq_save(flags); + if (!arch_spin_trylock(&lock)) + /* + * If there is already a trigger_all_cpu_backtrace() + * in progress, don't output double cpu dump infos. + */ + goto out_restore_irq; cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); @@ -564,4 +574,8 @@ void arch_trigger_all_cpu_backtrace(void) break; mdelay(1); } + + arch_spin_unlock(&lock); +out_restore_irq: + local_irq_restore(flags); } -- 1.7.2.3