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[PATCH] clocksource: Add verification (watchdog) helper

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The TSC needs to be verified against another clocksource.  Instead of using
hardwired assumptions of available hardware, provide a generic verification
mechanism.  The verification uses the best available clocksource and handles
the usability for high resolution timers / dynticks of the clocksource which
needs to be verified.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Thomas Gleixner 2007-02-16 01:27:43 -08:00 • committed by Linus Torvalds
parent 7e69f2b1ea
commit 5d8b34fdcb
5 changed files with 161 additions and 78 deletions
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45
kernel/timer.c
View file

@ -832,30 +832,33 @@ EXPORT_SYMBOL(do_settimeofday);
*
* Accumulates current time interval and initializes new clocksource
*/
static int change_clocksource(void)
static void change_clocksource(void)
{
struct clocksource *new;
cycle_t now;
u64 nsec;
new = clocksource_get_next();
if (clock != new) {
now = clocksource_read(new);
nsec = __get_nsec_offset();
timespec_add_ns(&xtime, nsec);
clock = new;
clock->cycle_last = now;
printk(KERN_INFO "Time: %s clocksource has been installed.\n",
clock->name);
return 1;
}
return 0;
new = clocksource_get_next();
if (clock == new)
return;
now = clocksource_read(new);
nsec = __get_nsec_offset();
timespec_add_ns(&xtime, nsec);
clock = new;
clock->cycle_last = now;
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
printk(KERN_INFO "Time: %s clocksource has been installed.\n",
clock->name);
}
#else
static inline int change_clocksource(void)
{
return 0;
}
static inline void change_clocksource(void) { }
#endif
/**
@ -869,7 +872,7 @@ int timekeeping_is_continuous(void)
do {
seq = read_seqbegin(&xtime_lock);
ret = clock->flags & CLOCK_SOURCE_IS_CONTINUOUS;
ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
} while (read_seqretry(&xtime_lock, seq));
@ -1124,11 +1127,7 @@ static void update_wall_time(void)
clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
/* check to see if there is a new clocksource to use */
if (change_clocksource()) {
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
}
change_clocksource();
}
/*