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Subject[PATCH 08/12] clocksource: Improve clocksource watchdog reporting
Date
The clocksource watchdog reporting has been less helpful
then desired, as it just printed the delta between
the two clocksources. This prevents any useful analysis
of why the skew occurred.

Thus this patch tries to improve the output when we
mark a clocksource as unstable, printing out the cycle
last and now values for both the current clocksource
and the watchdog clocksource. This will allow us to see
if the result was due to a false positive caused by
a problematic watchdog.

Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
kernel/time/clocksource.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index a491803..340461e 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -142,13 +142,6 @@ static void __clocksource_unstable(struct clocksource *cs)
schedule_work(&watchdog_work);
}

-static void clocksource_unstable(struct clocksource *cs, int64_t delta)
-{
- printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
- cs->name, delta);
- __clocksource_unstable(cs);
-}
-
/**
* clocksource_mark_unstable - mark clocksource unstable via watchdog
* @cs: clocksource to be marked unstable
@@ -174,7 +167,7 @@ void clocksource_mark_unstable(struct clocksource *cs)
static void clocksource_watchdog(unsigned long data)
{
struct clocksource *cs;
- cycle_t csnow, wdnow, delta;
+ cycle_t csnow, wdnow, cslast, wdlast, delta;
int64_t wd_nsec, cs_nsec;
int next_cpu, reset_pending;

@@ -213,6 +206,8 @@ static void clocksource_watchdog(unsigned long data)

delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
+ wdlast = cs->wd_last; /* save these in case we print them */
+ cslast = cs->cs_last;
cs->cs_last = csnow;
cs->wd_last = wdnow;

@@ -221,7 +216,12 @@ static void clocksource_watchdog(unsigned long data)

/* Check the deviation from the watchdog clocksource. */
if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
- clocksource_unstable(cs, cs_nsec - wd_nsec);
+ pr_warn("Watchdog: clocksource %s unstable\n", cs->name);
+ pr_warn(" %s wd_now: %llx wd_last: %llx mask: %llx\n",
+ watchdog->name, wdnow, wdlast, watchdog->mask);
+ pr_warn(" %s cs_now: %llx cs_last: %llx mask: %llx\n",
+ cs->name, csnow, cslast, cs->mask);
+ __clocksource_unstable(cs);
continue;
}

--
1.9.1


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