Messages in this thread | | | Subject | A question of perf NMI handler | From | Lin Ming <> | Date | Wed, 04 Aug 2010 17:21:10 +0800 |
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With nmi_watchdog enabled, perf_event_nmi_handler always return NOTIFY_STOP(active_events > 0), and the notifier call chain will not call further.
If it was not perf NMI, does the perf nmi handler may stop the real NMI handler get called because NOTIFY_STOP is returned??
static int __kprobes perf_event_nmi_handler(struct notifier_block *self, unsigned long cmd, void *__args) { struct die_args *args = __args; struct pt_regs *regs;
if (!atomic_read(&active_events)) ===> With nmi_watchdog enabled, active_events > 0 return NOTIFY_DONE;
switch (cmd) { case DIE_NMI: case DIE_NMI_IPI: break;
default: return NOTIFY_DONE; }
regs = args->regs;
apic_write(APIC_LVTPC, APIC_DM_NMI); /* * Can't rely on the handled return value to say it was our NMI, two * events could trigger 'simultaneously' raising two back-to-back NMIs. * * If the first NMI handles both, the latter will be empty and daze * the CPU. */ x86_pmu.handle_irq(regs);
return NOTIFY_STOP; }
Thanks, Lin Ming
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