Commit 9b498932 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Greg Kroah-Hartman

clockevents: prevent endless loop lockup

commit 1fb9b7d2 upstream

The C1E/HPET bug reports on AMDX2/RS690 systems where tracked down to a
too small value of the HPET minumum delta for programming an event.

The clockevents code needs to enforce an interrupt event on the clock event
device in some cases. The enforcement code was stupid and naive, as it just
added the minimum delta to the current time and tried to reprogram the device.
When the minimum delta is too small, then this loops forever.

Add a sanity check. Allow reprogramming to fail 3 times, then print a warning
and double the minimum delta value to make sure, that this does not happen again.
Use the same function for both tick-oneshot and tick-broadcast code.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 7f0a673a
...@@ -370,16 +370,8 @@ cpumask_t *tick_get_broadcast_oneshot_mask(void) ...@@ -370,16 +370,8 @@ cpumask_t *tick_get_broadcast_oneshot_mask(void)
static int tick_broadcast_set_event(ktime_t expires, int force) static int tick_broadcast_set_event(ktime_t expires, int force)
{ {
struct clock_event_device *bc = tick_broadcast_device.evtdev; struct clock_event_device *bc = tick_broadcast_device.evtdev;
ktime_t now = ktime_get();
int res;
for(;;) { return tick_dev_program_event(bc, expires, force);
res = clockevents_program_event(bc, expires, now);
if (!res || !force)
return res;
now = ktime_get();
expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
}
} }
int tick_resume_broadcast_oneshot(struct clock_event_device *bc) int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
......
...@@ -17,6 +17,8 @@ extern void tick_handle_periodic(struct clock_event_device *dev); ...@@ -17,6 +17,8 @@ extern void tick_handle_periodic(struct clock_event_device *dev);
extern void tick_setup_oneshot(struct clock_event_device *newdev, extern void tick_setup_oneshot(struct clock_event_device *newdev,
void (*handler)(struct clock_event_device *), void (*handler)(struct clock_event_device *),
ktime_t nextevt); ktime_t nextevt);
extern int tick_dev_program_event(struct clock_event_device *dev,
ktime_t expires, int force);
extern int tick_program_event(ktime_t expires, int force); extern int tick_program_event(ktime_t expires, int force);
extern void tick_oneshot_notify(void); extern void tick_oneshot_notify(void);
extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)); extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *));
......
...@@ -25,18 +25,42 @@ ...@@ -25,18 +25,42 @@
/** /**
* tick_program_event internal worker function * tick_program_event internal worker function
*/ */
static int __tick_program_event(struct clock_event_device *dev, int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
ktime_t expires, int force) int force)
{ {
ktime_t now = ktime_get(); ktime_t now = ktime_get();
int i;
while (1) { for (i = 0;;) {
int ret = clockevents_program_event(dev, expires, now); int ret = clockevents_program_event(dev, expires, now);
if (!ret || !force) if (!ret || !force)
return ret; return ret;
/*
* We tried 2 times to program the device with the given
* min_delta_ns. If that's not working then we double it
* and emit a warning.
*/
if (++i > 2) {
printk(KERN_WARNING "CE: __tick_program_event of %s is "
"stuck %llx %llx\n", dev->name ? dev->name : "?",
now.tv64, expires.tv64);
printk(KERN_WARNING
"CE: increasing min_delta_ns %ld to %ld nsec\n",
dev->min_delta_ns, dev->min_delta_ns << 1);
WARN_ON(1);
/* Double the min. delta and try again */
if (!dev->min_delta_ns)
dev->min_delta_ns = 5000;
else
dev->min_delta_ns <<= 1;
i = 0;
}
now = ktime_get(); now = ktime_get();
expires = ktime_add(now, ktime_set(0, dev->min_delta_ns)); expires = ktime_add_ns(now, dev->min_delta_ns);
} }
} }
...@@ -47,7 +71,7 @@ int tick_program_event(ktime_t expires, int force) ...@@ -47,7 +71,7 @@ int tick_program_event(ktime_t expires, int force)
{ {
struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
return __tick_program_event(dev, expires, force); return tick_dev_program_event(dev, expires, force);
} }
/** /**
...@@ -71,7 +95,7 @@ void tick_setup_oneshot(struct clock_event_device *newdev, ...@@ -71,7 +95,7 @@ void tick_setup_oneshot(struct clock_event_device *newdev,
{ {
newdev->event_handler = handler; newdev->event_handler = handler;
clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
__tick_program_event(newdev, next_event, 1); tick_dev_program_event(newdev, next_event, 1);
} }
/** /**
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment