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| author | Dongdong Deng <dongdong.deng@windriver.com> | 2011-01-04 22:38:08 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-01-05 14:22:57 +0100 |
| commit | 554ec063982752e9a569ab9189eeffa3d96731b2 (patch) | |
| tree | 1f27aba0e34881c1d8b428d18e1c1fbaa866c612 | |
| parent | 9ab181fa9ff73a38fccd0a4f1c40a38dfe62b535 (diff) | |
| download | linux-554ec063982752e9a569ab9189eeffa3d96731b2.tar.bz2 | |
x86: Avoid calling arch_trigger_all_cpu_backtrace() at the same time
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 taken as unknown reason NMI interrupts.
This patch uses a test_and_set to avoid the problem, and stop
the arch_trigger_all_cpu_backtrace() from calling to avoid
dumping a 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: fweisbec@gmail.com
LKML-Reference: <1294198689-15447-2-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Don Zickus <dzickus@redhat.com>
| -rw-r--r-- | arch/x86/kernel/apic/hw_nmi.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index 2b40a6045da2..72ec29e1ae06 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -28,10 +28,20 @@ u64 hw_nmi_get_sample_period(void) /* For reliability, we're prepared to waste bits here. */ static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; +/* "in progress" flag of arch_trigger_all_cpu_backtrace */ +static unsigned long backtrace_flag; + void arch_trigger_all_cpu_backtrace(void) { int i; + 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. + */ + return; + cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); printk(KERN_INFO "sending NMI to all CPUs:\n"); @@ -43,6 +53,9 @@ void arch_trigger_all_cpu_backtrace(void) break; mdelay(1); } + + clear_bit(0, &backtrace_flag); + smp_mb__after_clear_bit(); } static int __kprobes |