lkml.org 
[lkml]   [2010]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[V3 PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at the same time on SMP
    Date
    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 <dongdong.deng@windriver.com>
    Reviewed-by: Bruce Ashfield <bruce.ashfield@windriver.com>
    CC: Thomas Gleixner <tglx@linutronix.de>
    CC: Ingo Molnar <mingo@redhat.com>
    CC: "H. Peter Anvin" <hpa@zytor.com>
    CC: x86@kernel.org
    CC: linux-kernel@vger.kernel.org
    Signed-off-by: Don Zickus <dzickus@redhat.com>
    ---
    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..bfdab3b 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 unsigned long 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 (test_and_set_bit(0, &backtrace_flag))
    + /*
    + * 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);
    }
    +
    + clear_bit(0, &backtrace_flag);
    +
    +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..bd9cb79 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 unsigned long 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 (test_and_set_bit(0, &backtrace_flag))
    + /*
    + * 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);
    }
    +
    + clear_bit(0, &backtrace_flag);
    +
    +out_restore_irq:
    + local_irq_restore(flags);
    }
    --
    1.6.0.4


    \
     
     \ /
      Last update: 2010-11-11 12:03    [W:0.025 / U:0.172 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site