Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932256Ab0KKCUv (ORCPT ); Wed, 10 Nov 2010 21:20:51 -0500 Received: from mail.windriver.com ([147.11.1.11]:62315 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932117Ab0KKCUu (ORCPT ); Wed, 10 Nov 2010 21:20:50 -0500 From: Dongdong Deng To: mingo@elte.hu, dzickus@redhat.com Cc: peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, dongdong.deng@windriver.com Subject: [PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at the same time on SMP Date: Thu, 11 Nov 2010 10:20:42 +0800 Message-Id: <1289442042-2515-1-git-send-email-dongdong.deng@windriver.com> X-Mailer: git-send-email 1.6.0.4 X-OriginalArrivalTime: 11 Nov 2010 02:20:10.0066 (UTC) FILETIME=[F6EDBB20:01CB8146] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4043 Lines: 131 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 | 23 +++++++++++++++++++++++ arch/x86/kernel/apic/nmi.c | 23 +++++++++++++++++++++++ 2 files changed, 46 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index cefd694..6084c3b 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -26,9 +26,27 @@ u64 hw_nmi_get_sample_period(void) } #ifdef ARCH_HAS_NMI_WATCHDOG +/* "in progress" flag of arch_trigger_all_cpu_backtrace */ +static int backtrace_flag; + void arch_trigger_all_cpu_backtrace(void) { int i; + unsigned long flags; + + /* + * Have to disable irq here, as the + * arch_trigger_all_cpu_backtrace() could be + * triggered by "spin_lock()" with irqs on. + */ + local_irq_save(flags); + + if (cmpxchg(&backtrace_flag, 0, 1) != 0) + /* + * If there is already a trigger_all_cpu_backtrace() in progress + * (backtrace_flag == 1), don't output double cpu dump infos. + */ + goto out_restore_irq; cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); @@ -41,6 +59,11 @@ void arch_trigger_all_cpu_backtrace(void) break; mdelay(1); } + + cmpxchg(&backtrace_flag, 1, 0); + +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 c90041c..2d4b3a1 100644 --- a/arch/x86/kernel/apic/nmi.c +++ b/arch/x86/kernel/apic/nmi.c @@ -549,9 +549,27 @@ int do_nmi_callback(struct pt_regs *regs, int cpu) return 0; } +/* "in progress" flag of arch_trigger_all_cpu_backtrace */ +static int backtrace_flag; + void arch_trigger_all_cpu_backtrace(void) { int i; + unsigned long flags; + + /* + * Have to disable irq here, as the + * arch_trigger_all_cpu_backtrace() could be + * triggered by "spin_lock()" with irqs on. + */ + local_irq_save(flags); + + if (cmpxchg(&backtrace_flag, 0, 1) != 0) + /* + * If there is already a trigger_all_cpu_backtrace() in progress + * (backtrace_flag == 1), don't output double cpu dump infos. + */ + goto out_restore_irq; cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); @@ -564,4 +582,9 @@ void arch_trigger_all_cpu_backtrace(void) break; mdelay(1); } + + cmpxchg(&backtrace_flag, 1, 0); + +out_restore_irq: + local_irq_restore(flags); } -- 1.6.0.4 -- 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/