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[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 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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4
arch/i386/Kconfig
View File

@ -18,6 +18,10 @@ config GENERIC_TIME
bool
default y
config CLOCKSOURCE_WATCHDOG
bool
default y
config LOCKDEP_SUPPORT
bool
default y

49
arch/i386/kernel/tsc.c
View File

@ -344,49 +344,6 @@ static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
{}
};
#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
static struct timer_list verify_tsc_freq_timer;
/* XXX - Probably should add locking */
static void verify_tsc_freq(unsigned long unused)
{
static u64 last_tsc;
static unsigned long last_jiffies;
u64 now_tsc, interval_tsc;
unsigned long now_jiffies, interval_jiffies;
if (check_tsc_unstable())
return;
rdtscll(now_tsc);
now_jiffies = jiffies;
if (!last_jiffies) {
goto out;
}
interval_jiffies = now_jiffies - last_jiffies;
interval_tsc = now_tsc - last_tsc;
interval_tsc *= HZ;
do_div(interval_tsc, cpu_khz*1000);
if (interval_tsc < (interval_jiffies * 3 / 4)) {
printk("TSC appears to be running slowly. "
"Marking it as unstable\n");
mark_tsc_unstable();
return;
}
out:
last_tsc = now_tsc;
last_jiffies = now_jiffies;
/* set us up to go off on the next interval: */
mod_timer(&verify_tsc_freq_timer,
jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
}
/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.
@ -424,12 +381,6 @@ static int __init init_tsc_clocksource(void)
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
}
init_timer(&verify_tsc_freq_timer);
verify_tsc_freq_timer.function = verify_tsc_freq;
verify_tsc_freq_timer.expires =
jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
add_timer(&verify_tsc_freq_timer);
return clocksource_register(&clocksource_tsc);
}

15
include/linux/clocksource.h
View File

@ -12,11 +12,13 @@
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/list.h>
#include <linux/timer.h>
#include <asm/div64.h>
#include <asm/io.h>
/* clocksource cycle base type */
typedef u64 cycle_t;
struct clocksource;
/**
* struct clocksource - hardware abstraction for a free running counter
@ -62,13 +64,22 @@ struct clocksource {
cycle_t cycle_last, cycle_interval;
u64 xtime_nsec, xtime_interval;
s64 error;
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
/* Watchdog related data, used by the framework */
struct list_head wd_list;
cycle_t wd_last;
#endif
};
/*
* Clock source flags bits::
*/
#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
#define CLOCK_SOURCE_MUST_VERIFY 0x02
#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
#define CLOCK_SOURCE_MUST_VERIFY 0x02
#define CLOCK_SOURCE_WATCHDOG 0x10
#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
/* simplify initialization of mask field */
#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)

126
kernel/time/clocksource.c
View File

@ -63,9 +63,116 @@ static int __init clocksource_done_booting(void)
finished_booting = 1;
return 0;
}
late_initcall(clocksource_done_booting);
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
static LIST_HEAD(watchdog_list);
static struct clocksource *watchdog;
static struct timer_list watchdog_timer;
static DEFINE_SPINLOCK(watchdog_lock);
static cycle_t watchdog_last;
/*
* Interval: 0.5sec Treshold: 0.0625s
*/
#define WATCHDOG_INTERVAL (HZ >> 1)
#define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
{
if (delta > -WATCHDOG_TRESHOLD && delta < WATCHDOG_TRESHOLD)
return;
printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
cs->name, delta);
cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
clocksource_change_rating(cs, 0);
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
list_del(&cs->wd_list);
}
static void clocksource_watchdog(unsigned long data)
{
struct clocksource *cs, *tmp;
cycle_t csnow, wdnow;
int64_t wd_nsec, cs_nsec;
spin_lock(&watchdog_lock);
wdnow = watchdog->read();
wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
watchdog_last = wdnow;
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
csnow = cs->read();
/* Initialized ? */
if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
}
cs->flags |= CLOCK_SOURCE_WATCHDOG;
cs->wd_last = csnow;
} else {
cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
cs->wd_last = csnow;
/* Check the delta. Might remove from the list ! */
clocksource_ratewd(cs, cs_nsec - wd_nsec);
}
}
if (!list_empty(&watchdog_list)) {
__mod_timer(&watchdog_timer,
watchdog_timer.expires + WATCHDOG_INTERVAL);
}
spin_unlock(&watchdog_lock);
}
static void clocksource_check_watchdog(struct clocksource *cs)
{
struct clocksource *cse;
unsigned long flags;
spin_lock_irqsave(&watchdog_lock, flags);
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
int started = !list_empty(&watchdog_list);
list_add(&cs->wd_list, &watchdog_list);
if (!started && watchdog) {
watchdog_last = watchdog->read();
watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
add_timer(&watchdog_timer);
}
} else if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) {
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
if (!watchdog || cs->rating > watchdog->rating) {
if (watchdog)
del_timer(&watchdog_timer);
watchdog = cs;
init_timer(&watchdog_timer);
watchdog_timer.function = clocksource_watchdog;
/* Reset watchdog cycles */
list_for_each_entry(cse, &watchdog_list, wd_list)
cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
/* Start if list is not empty */
if (!list_empty(&watchdog_list)) {
watchdog_last = watchdog->read();
watchdog_timer.expires =
jiffies + WATCHDOG_INTERVAL;
add_timer(&watchdog_timer);
}
}
}
spin_unlock_irqrestore(&watchdog_lock, flags);
}
#else
static void clocksource_check_watchdog(struct clocksource *cs)
{
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
}
#endif
/**
* clocksource_get_next - Returns the selected clocksource
*
@ -94,13 +201,21 @@ struct clocksource *clocksource_get_next(void)
*/
static struct clocksource *select_clocksource(void)
{
struct clocksource *next;
if (list_empty(&clocksource_list))
return NULL;
if (clocksource_override)
return clocksource_override;
next = clocksource_override;
else
next = list_entry(clocksource_list.next, struct clocksource,
list);
return list_entry(clocksource_list.next, struct clocksource, list);
if (next == curr_clocksource)
return NULL;
return next;
}
/*
@ -138,13 +253,15 @@ static int clocksource_enqueue(struct clocksource *c)
int clocksource_register(struct clocksource *c)
{
unsigned long flags;
int ret = 0;
int ret;
spin_lock_irqsave(&clocksource_lock, flags);
ret = clocksource_enqueue(c);
if (!ret)
next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);
if (!ret)
clocksource_check_watchdog(c);
return ret;
}
EXPORT_SYMBOL(clocksource_register);
@ -159,6 +276,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
spin_lock_irqsave(&clocksource_lock, flags);
list_del(&cs->list);
cs->rating = rating;
clocksource_enqueue(cs);
next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);

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();
}
/*