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Commit bb29ab26 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: x86, track TSC-unstable events 



track TSC-unstable events and propagate it to the scheduler code.
Also allow sched_clock() to be used when the TSC is unstable,
the rq_clock() wrapper creates a reliable clock out of it.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent dd41f596

arch/i386/kernel/tsc.c

+8 −1
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
 * See comments there for proper credits.

 */



#include <linux/sched.h>

#include <linux/clocksource.h>

#include <linux/workqueue.h>

#include <linux/cpufreq.h>
@@ -106,8 +107,13 @@ unsigned long long sched_clock(void) 


	/*

	 * Fall back to jiffies if there's no TSC available:

	 * ( But note that we still use it if the TSC is marked

	 *   unstable. We do this because unlike Time Of Day,

	 *   the scheduler clock tolerates small errors and it's

	 *   very important for it to be as fast as the platform

	 *   can achive it. )

	 */

	if (unlikely(!tsc_enabled))

	if (unlikely(!tsc_enabled && !tsc_unstable))

		/* No locking but a rare wrong value is not a big deal: */

		return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
@@ -277,6 +283,7 @@ static struct clocksource clocksource_tsc = { 


void mark_tsc_unstable(char *reason)

{

	sched_clock_unstable_event();

	if (!tsc_unstable) {

		tsc_unstable = 1;

		tsc_enabled = 0;

include/linux/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -1321,6 +1321,8 @@ extern void sched_exec(void); 
#define sched_exec()   {}

#endif



extern void sched_clock_unstable_event(void);



#ifdef CONFIG_HOTPLUG_CPU

extern void idle_task_exit(void);

#else

kernel/sched.c

+7 −0
Original line number Diff line number Diff line
@@ -67,6 +67,13 @@ unsigned long long __attribute__((weak)) sched_clock(void) 
	return (unsigned long long)jiffies * (1000000000 / HZ);

}



/*

 * CPU frequency is/was unstable - start new by setting prev_clock_raw:

 */

void sched_clock_unstable_event(void)

{

}



/*

 * Convert user-nice values [ -20 ... 0 ... 19 ]

 * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],