Messages in this thread | | | Date | Fri, 23 Jan 2015 15:30:06 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 08/12] time: Add warnings when overflows or underflows are observed |
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On Thu, Jan 22, 2015 at 04:09:23PM -0800, John Stultz wrote: > #ifdef CONFIG_DEBUG_TIMEKEEPING > +#define WARNINGFREQ (HZ*300) /* 5 minute rate-limiting */ > +/* > + * These simple flag variables are managed > + * without locks, which is racy, but ok since > + * we don't really care about being super > + * precise about how many events were seen, > + * just that a problem was observed. > + */ > +static int timekeeping_underflow_seen; > +static int timekeeping_overflow_seen; > + > static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset) > { > > cycle_t max_cycles = tk->tkr.clock->max_cycles; > const char *name = tk->tkr.clock->name; > + static long last_warning; /* we always hold write on timekeeper lock */ > > if (offset > max_cycles) > printk_deferred("ERROR: cycle offset (%lld) is larger then" > @@ -133,28 +145,60 @@ static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset) > printk_deferred("WARNING: cycle offset (%lld) is past" > " the %s 50%% safety margin (%lld)\n", > offset, name, max_cycles>>1); > + > + if (timekeeping_underflow_seen) { > + if (jiffies - last_warning > WARNINGFREQ) { > + printk_deferred("WARNING: Clocksource underflow observed\n"); > + last_warning = jiffies; > + } > + timekeeping_underflow_seen = 0; > + } > + if (timekeeping_overflow_seen) { > + if (jiffies - last_warning > WARNINGFREQ) { > + printk_deferred("WARNING: Clocksource overflow observed\n"); > + last_warning = jiffies; > + } > + timekeeping_overflow_seen = 0; > + } > + > }
Ah, ignore my last comment. Excellent!
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