From: Peter Zijlstra <peterz@infradead.org>
To: John Stultz <john.stultz@linaro.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dave Jones <davej@codemonkey.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Richard Cochran <richardcochran@gmail.com>,
Prarit Bhargava <prarit@redhat.com>,
Stephen Boyd <sboyd@codeaurora.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 08/12] time: Add warnings when overflows or underflows are observed
Date: Fri, 23 Jan 2015 15:30:06 +0100 [thread overview]
Message-ID: <20150123143006.GC23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1421971767-17707-9-git-send-email-john.stultz@linaro.org>
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!
next prev parent reply other threads:[~2015-01-23 14:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 0:09 [PATCH 00/12][RFC] Increased clocksource validation and cleanups (v2) John Stultz
2015-01-23 0:09 ` [PATCH 01/12] clocksource: Simplify clocks_calc_max_nsecs logic John Stultz
2015-01-23 0:09 ` [PATCH 02/12] clocksource: Simplify logic around clocksource wrapping saftey margins John Stultz
2015-01-23 0:09 ` [PATCH 03/12] clocksource: Remove clocksource_max_deferment() John Stultz
2015-01-23 0:09 ` [PATCH 04/12] clocksource: Add max_cycles to clocksource structure John Stultz
2015-01-23 0:09 ` [PATCH 05/12] time: Add debugging checks to warn if we see delays John Stultz
2015-01-23 14:27 ` Peter Zijlstra
2015-01-23 0:09 ` [PATCH 06/12] time: Add infrastructure to cap clocksource reads to the max_cycles value John Stultz
2015-01-23 14:28 ` Peter Zijlstra
2015-01-24 17:35 ` Richard Cochran
2015-01-23 0:09 ` [PATCH 07/12] time: Try to catch clocksource delta underflows John Stultz
2015-01-23 0:09 ` [PATCH 08/12] time: Add warnings when overflows or underflows are observed John Stultz
2015-01-23 14:30 ` Peter Zijlstra [this message]
2015-01-23 0:09 ` [PATCH 09/12] clocksource: Improve clocksource watchdog reporting John Stultz
2015-01-23 0:09 ` [PATCH 10/12] clocksource: Mostly kill clocksource_register() John Stultz
2015-01-23 0:09 ` [PATCH 11/12] sparc: Convert to using clocksource_register_hz() John Stultz
2015-01-27 1:18 ` David Miller
2015-01-23 0:09 ` [PATCH 12/12] clocksource: Add some debug info about clocksources being registered John Stultz
2015-03-07 2:49 [PATCH 00/12] Increased clocksource validation and cleanups (v3) John Stultz
2015-03-07 2:49 ` [PATCH 08/12] time: Add warnings when overflows or underflows are observed John Stultz
2015-03-07 9:40 ` Ingo Molnar
2015-03-09 16:50 ` John Stultz
2015-03-10 5:05 ` Ingo Molnar
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