Messages in this thread | | | Date | Tue, 6 Apr 2010 19:31:15 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [watchdog] combine nmi_watchdog and softlockup |
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On Tue, Apr 06, 2010 at 04:13:30PM +0200, Frederic Weisbecker wrote: [...] > > +static int watchdog_enable(int cpu) > > +{ > > + struct perf_event_attr *wd_attr; > > + struct perf_event *event = per_cpu(watchdog_ev, cpu); > > + struct task_struct *p = per_cpu(softlockup_watchdog, cpu); > > + > > + /* is it already setup and enabled? */ > > + if (event && event->state > PERF_EVENT_STATE_OFF) > > + goto out; > > + > > + /* it is setup but not enabled */ > > + if (event != NULL) > > + goto out_enable; > > + > > + /* Try to register using hardware perf events first */ > > + wd_attr = &wd_hw_attr; > > + wd_attr->sample_period = hw_nmi_get_sample_period(); > > + event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback); > > + if (!IS_ERR(event)) { > > + printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n"); > > + goto out_save; > > + } > > + > > + /* hardware doesn't exist or not supported, fallback to software events */ > > + printk(KERN_INFO "NMI watchdog: hardware not available, trying software events\n"); > > + wd_attr = &wd_sw_attr; > > + wd_attr->sample_period = softlockup_thresh * NSEC_PER_SEC; > > + event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback); > > I fear the cpu clock is not going to help you detecting any hard lockups. > If you're stuck in an interrupt or an irq disabled loop, your cpu clock is > not going to fire. >
I guess it's not supposed to. For such cases only nmi irqs may help for which the perf events are there (/me need to check if we program apic timer for anything like that). But it should help for other deadlocks. Or I miss something?
-- Cyrill
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