[PATCH] clocksource: Add verification (watchdog) helper
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
Linus Torvalds
parent
7e69f2b1ea
commit
5d8b34fdcb
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@ -18,6 +18,10 @@ config GENERIC_TIME
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bool
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default y
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config CLOCKSOURCE_WATCHDOG
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bool
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default y
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config LOCKDEP_SUPPORT
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bool
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default y
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@ -344,49 +344,6 @@ static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
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{}
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};
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#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
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static struct timer_list verify_tsc_freq_timer;
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/* XXX - Probably should add locking */
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static void verify_tsc_freq(unsigned long unused)
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{
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static u64 last_tsc;
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static unsigned long last_jiffies;
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u64 now_tsc, interval_tsc;
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unsigned long now_jiffies, interval_jiffies;
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if (check_tsc_unstable())
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return;
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rdtscll(now_tsc);
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now_jiffies = jiffies;
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if (!last_jiffies) {
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goto out;
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}
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interval_jiffies = now_jiffies - last_jiffies;
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interval_tsc = now_tsc - last_tsc;
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interval_tsc *= HZ;
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do_div(interval_tsc, cpu_khz*1000);
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if (interval_tsc < (interval_jiffies * 3 / 4)) {
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printk("TSC appears to be running slowly. "
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"Marking it as unstable\n");
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mark_tsc_unstable();
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return;
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}
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out:
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last_tsc = now_tsc;
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last_jiffies = now_jiffies;
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/* set us up to go off on the next interval: */
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mod_timer(&verify_tsc_freq_timer,
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jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
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}
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/*
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* Make an educated guess if the TSC is trustworthy and synchronized
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* over all CPUs.
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@ -424,12 +381,6 @@ static int __init init_tsc_clocksource(void)
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clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
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}
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init_timer(&verify_tsc_freq_timer);
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verify_tsc_freq_timer.function = verify_tsc_freq;
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verify_tsc_freq_timer.expires =
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jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
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add_timer(&verify_tsc_freq_timer);
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return clocksource_register(&clocksource_tsc);
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}
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@ -12,11 +12,13 @@
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#include <linux/timex.h>
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#include <linux/time.h>
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#include <linux/list.h>
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#include <linux/timer.h>
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#include <asm/div64.h>
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#include <asm/io.h>
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/* clocksource cycle base type */
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typedef u64 cycle_t;
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struct clocksource;
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/**
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* struct clocksource - hardware abstraction for a free running counter
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@ -62,13 +64,22 @@ struct clocksource {
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cycle_t cycle_last, cycle_interval;
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u64 xtime_nsec, xtime_interval;
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s64 error;
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#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
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/* Watchdog related data, used by the framework */
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struct list_head wd_list;
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cycle_t wd_last;
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#endif
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};
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/*
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* Clock source flags bits::
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*/
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#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
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#define CLOCK_SOURCE_MUST_VERIFY 0x02
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#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
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#define CLOCK_SOURCE_MUST_VERIFY 0x02
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#define CLOCK_SOURCE_WATCHDOG 0x10
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#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
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/* simplify initialization of mask field */
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#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
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@ -63,9 +63,116 @@ static int __init clocksource_done_booting(void)
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finished_booting = 1;
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return 0;
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}
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late_initcall(clocksource_done_booting);
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#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
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static LIST_HEAD(watchdog_list);
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static struct clocksource *watchdog;
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static struct timer_list watchdog_timer;
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static DEFINE_SPINLOCK(watchdog_lock);
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static cycle_t watchdog_last;
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/*
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* Interval: 0.5sec Treshold: 0.0625s
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*/
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#define WATCHDOG_INTERVAL (HZ >> 1)
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#define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
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static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
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{
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if (delta > -WATCHDOG_TRESHOLD && delta < WATCHDOG_TRESHOLD)
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return;
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printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
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cs->name, delta);
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cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
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clocksource_change_rating(cs, 0);
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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list_del(&cs->wd_list);
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}
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static void clocksource_watchdog(unsigned long data)
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{
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struct clocksource *cs, *tmp;
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cycle_t csnow, wdnow;
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int64_t wd_nsec, cs_nsec;
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spin_lock(&watchdog_lock);
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wdnow = watchdog->read();
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wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
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watchdog_last = wdnow;
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list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
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csnow = cs->read();
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/* Initialized ? */
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if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
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if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
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(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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}
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cs->flags |= CLOCK_SOURCE_WATCHDOG;
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cs->wd_last = csnow;
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} else {
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cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
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cs->wd_last = csnow;
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/* Check the delta. Might remove from the list ! */
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clocksource_ratewd(cs, cs_nsec - wd_nsec);
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}
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}
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if (!list_empty(&watchdog_list)) {
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__mod_timer(&watchdog_timer,
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watchdog_timer.expires + WATCHDOG_INTERVAL);
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}
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spin_unlock(&watchdog_lock);
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}
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static void clocksource_check_watchdog(struct clocksource *cs)
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{
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struct clocksource *cse;
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
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int started = !list_empty(&watchdog_list);
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list_add(&cs->wd_list, &watchdog_list);
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if (!started && watchdog) {
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watchdog_last = watchdog->read();
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watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
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add_timer(&watchdog_timer);
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}
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} else if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) {
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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if (!watchdog || cs->rating > watchdog->rating) {
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if (watchdog)
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del_timer(&watchdog_timer);
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watchdog = cs;
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init_timer(&watchdog_timer);
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watchdog_timer.function = clocksource_watchdog;
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/* Reset watchdog cycles */
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list_for_each_entry(cse, &watchdog_list, wd_list)
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cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
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/* Start if list is not empty */
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if (!list_empty(&watchdog_list)) {
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watchdog_last = watchdog->read();
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watchdog_timer.expires =
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jiffies + WATCHDOG_INTERVAL;
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add_timer(&watchdog_timer);
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}
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}
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}
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spin_unlock_irqrestore(&watchdog_lock, flags);
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}
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#else
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static void clocksource_check_watchdog(struct clocksource *cs)
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{
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if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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}
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#endif
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/**
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* clocksource_get_next - Returns the selected clocksource
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*
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@ -94,13 +201,21 @@ struct clocksource *clocksource_get_next(void)
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*/
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static struct clocksource *select_clocksource(void)
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{
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struct clocksource *next;
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if (list_empty(&clocksource_list))
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return NULL;
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if (clocksource_override)
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return clocksource_override;
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next = clocksource_override;
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else
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next = list_entry(clocksource_list.next, struct clocksource,
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list);
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return list_entry(clocksource_list.next, struct clocksource, list);
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if (next == curr_clocksource)
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return NULL;
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return next;
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}
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/*
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@ -138,13 +253,15 @@ static int clocksource_enqueue(struct clocksource *c)
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int clocksource_register(struct clocksource *c)
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{
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unsigned long flags;
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int ret = 0;
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int ret;
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spin_lock_irqsave(&clocksource_lock, flags);
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ret = clocksource_enqueue(c);
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if (!ret)
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next_clocksource = select_clocksource();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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if (!ret)
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clocksource_check_watchdog(c);
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return ret;
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}
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EXPORT_SYMBOL(clocksource_register);
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@ -159,6 +276,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
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spin_lock_irqsave(&clocksource_lock, flags);
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list_del(&cs->list);
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cs->rating = rating;
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clocksource_enqueue(cs);
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next_clocksource = select_clocksource();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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@ -832,30 +832,33 @@ EXPORT_SYMBOL(do_settimeofday);
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*
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* Accumulates current time interval and initializes new clocksource
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*/
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static int change_clocksource(void)
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static void change_clocksource(void)
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{
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struct clocksource *new;
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cycle_t now;
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u64 nsec;
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new = clocksource_get_next();
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if (clock != new) {
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now = clocksource_read(new);
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nsec = __get_nsec_offset();
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timespec_add_ns(&xtime, nsec);
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clock = new;
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clock->cycle_last = now;
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printk(KERN_INFO "Time: %s clocksource has been installed.\n",
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clock->name);
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return 1;
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}
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return 0;
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new = clocksource_get_next();
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if (clock == new)
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return;
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now = clocksource_read(new);
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nsec = __get_nsec_offset();
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timespec_add_ns(&xtime, nsec);
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clock = new;
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clock->cycle_last = now;
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clock->error = 0;
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clock->xtime_nsec = 0;
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clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
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printk(KERN_INFO "Time: %s clocksource has been installed.\n",
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clock->name);
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}
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#else
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static inline int change_clocksource(void)
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{
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return 0;
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}
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static inline void change_clocksource(void) { }
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#endif
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/**
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@ -869,7 +872,7 @@ int timekeeping_is_continuous(void)
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do {
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seq = read_seqbegin(&xtime_lock);
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ret = clock->flags & CLOCK_SOURCE_IS_CONTINUOUS;
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ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
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} while (read_seqretry(&xtime_lock, seq));
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@ -1124,11 +1127,7 @@ static void update_wall_time(void)
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clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
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/* check to see if there is a new clocksource to use */
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if (change_clocksource()) {
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clock->error = 0;
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clock->xtime_nsec = 0;
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clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
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}
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change_clocksource();
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}
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/*
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