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Commit 12907fbb authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent cb42c9a3

arch/x86/kernel/tsc.c

+11 −0
Original line number Diff line number Diff line
@@ -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)

include/linux/clocksource.h

+3 −0
Original line number Diff line number Diff line
@@ -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

kernel/time/clocksource.c

+4 −0
Original line number Diff line number Diff line
@@ -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);

}