From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754010Ab0JKK04 (ORCPT ); Mon, 11 Oct 2010 06:26:56 -0400 Received: from mail.windriver.com ([147.11.1.11]:44226 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750963Ab0JKK0z (ORCPT ); Mon, 11 Oct 2010 06:26:55 -0400 From: Dongdong Deng To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, dongdong.deng@windriver.com, bruce.ashfield@windriver.com Subject: [PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at the same time on SMP Date: Mon, 11 Oct 2010 18:31:51 +0800 Message-Id: <1286793111-27579-1-git-send-email-dongdong.deng@windriver.com> X-Mailer: git-send-email 1.6.0.4 X-OriginalArrivalTime: 11 Oct 2010 10:25:22.0381 (UTC) FILETIME=[9C6A37D0:01CB692E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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); } -- 1.6.0.4