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hrtimer: mark migration state 

Impact: during migration active hrtimers can be seen as inactive

The migration code removes the hrtimers from the queues of the dead
CPU and sets the state temporary to INACTIVE. The enqueue code sets it
to ACTIVE/PENDING again.

Prevent that the wrong state can be seen by using a separate migration
state bit.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2008-09-29 15:44:46 +02:00
parent 41e1022eae
commit b00c1a99e7
2 changed files with 13 additions and 3 deletions
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4
include/linux/hrtimer.h
View File

@ -67,9 +67,10 @@ enum hrtimer_cb_mode {
* 0x02 callback function running
* 0x04 callback pending (high resolution mode)
*
* Special case:
* Special cases:
* 0x03 callback function running and enqueued
* (was requeued on another CPU)
* 0x09 timer was migrated on CPU hotunplug
* The "callback function running and enqueued" status is only possible on
* SMP. It happens for example when a posix timer expired and the callback
* queued a signal. Between dropping the lock which protects the posix timer
@ -87,6 +88,7 @@ enum hrtimer_cb_mode {
#define HRTIMER_STATE_ENQUEUED 0x01
#define HRTIMER_STATE_CALLBACK 0x02
#define HRTIMER_STATE_PENDING 0x04
#define HRTIMER_STATE_MIGRATE 0x08
/**
* struct hrtimer - the basic hrtimer structure

12
kernel/hrtimer.c
View File

@ -1602,7 +1602,13 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
timer = rb_entry(node, struct hrtimer, node);
BUG_ON(hrtimer_callback_running(timer));
debug_hrtimer_deactivate(timer);
__remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE, 0);
/*
* Mark it as STATE_MIGRATE not INACTIVE otherwise the
* timer could be seen as !active and just vanish away
* under us on another CPU
*/
__remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
timer->base = new_base;
/*
* Enqueue the timer. Allow reprogramming of the event device
@ -1620,13 +1626,15 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
* state, we need to do that otherwise we end up with
* a stale timer.
*/
if (timer->state == HRTIMER_STATE_INACTIVE) {
if (timer->state == HRTIMER_STATE_MIGRATE) {
timer->state = HRTIMER_STATE_PENDING;
list_add_tail(&timer->cb_entry,
&new_base->cpu_base->cb_pending);
raise = 1;
}
#endif
/* Clear the migration state bit */
timer->state &= ~HRTIMER_STATE_MIGRATE;
}
return raise;
}