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sched/clock, clocksource: Add optional cs::mark_unstable() method 

PeterZ reported that we'd fail to mark the TSC unstable when the
clocksource watchdog finds it unsuitable.

Allow a clocksource to run a custom action when its being marked
unstable and hook up the TSC unstable code.

Reported-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
zero-colors
Thomas Gleixner 2016-12-15 11:44:28 +01:00 committed by Ingo Molnar
parent cb42c9a3eb
commit 12907fbb1a
3 changed files with 18 additions and 0 deletions
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11
arch/x86/kernel/tsc.c
View File

@ -1106,6 +1106,16 @@ static u64 read_tsc(struct clocksource *cs)
return (u64)rdtsc_ordered();
}
static void tsc_cs_mark_unstable(struct clocksource *cs)
{
if (tsc_unstable)
return;
tsc_unstable = 1;
clear_sched_clock_stable();
disable_sched_clock_irqtime();
pr_info("Marking TSC unstable due to clocksource watchdog\n");
}
/*
* .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
*/
@ -1118,6 +1128,7 @@ static struct clocksource clocksource_tsc = {
CLOCK_SOURCE_MUST_VERIFY,
.archdata = { .vclock_mode = VCLOCK_TSC },
.resume = tsc_resume,
.mark_unstable = tsc_cs_mark_unstable,
};
void mark_tsc_unstable(char *reason)

3
include/linux/clocksource.h
View File

@ -62,6 +62,8 @@ struct module;
* @archdata: arch-specific data
* @suspend: suspend function for the clocksource, if necessary
* @resume: resume function for the clocksource, if necessary
* @mark_unstable: Optional function to inform the clocksource driver that
* the watchdog marked the clocksource unstable
* @owner: module reference, must be set by clocksource in modules
*
* Note: This struct is not used in hotpathes of the timekeeping code
@ -93,6 +95,7 @@ struct clocksource {
unsigned long flags;
void (*suspend)(struct clocksource *cs);
void (*resume)(struct clocksource *cs);
void (*mark_unstable)(struct clocksource *cs);
/* private: */
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG

4
kernel/time/clocksource.c
View File

@ -141,6 +141,10 @@ static void __clocksource_unstable(struct clocksource *cs)
{
cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
cs->flags |= CLOCK_SOURCE_UNSTABLE;
if (cs->mark_unstable)
cs->mark_unstable(cs);
if (finished_booting)
schedule_work(&watchdog_work);
}