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hrtimer: prevent migration of per CPU hrtimers

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Impact: per CPU hrtimers can be migrated from a dead CPU

The hrtimer code has no knowledge about per CPU timers, but we need to
prevent the migration of such timers and warn when such a timer is
active at migration time.

Explicitely mark the timers as per CPU and use a more understandable
mode descriptor for the interrupts safe unlocked callback mode, which
is used by hrtimer_sleeper and the scheduler code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2008-09-29 15:47:42 +02:00
parent b00c1a99e7
commit ccc7dadf73
5 changed files with 40 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

37
kernel/hrtimer.c
View file

@ -672,13 +672,14 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
*/
BUG_ON(timer->function(timer) != HRTIMER_NORESTART);
return 1;
case HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:
case HRTIMER_CB_IRQSAFE_PERCPU:
case HRTIMER_CB_IRQSAFE_UNLOCKED:
/*
* This is solely for the sched tick emulation with
* dynamic tick support to ensure that we do not
* restart the tick right on the edge and end up with
* the tick timer in the softirq ! The calling site
* takes care of this.
* takes care of this. Also used for hrtimer sleeper !
*/
debug_hrtimer_deactivate(timer);
return 1;
@ -1245,7 +1246,8 @@ static void __run_hrtimer(struct hrtimer *timer)
timer_stats_account_hrtimer(timer);
fn = timer->function;
if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {
if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU ||
timer->cb_mode == HRTIMER_CB_IRQSAFE_UNLOCKED) {
/*
* Used for scheduler timers, avoid lock inversion with
* rq->lock and tasklist_lock.
@ -1452,7 +1454,7 @@ void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
sl->timer.function = hrtimer_wakeup;
sl->task = task;
#ifdef CONFIG_HIGH_RES_TIMERS
sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_UNLOCKED;
#endif
}
@ -1592,7 +1594,7 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
#ifdef CONFIG_HOTPLUG_CPU
static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
struct hrtimer_clock_base *new_base)
struct hrtimer_clock_base *new_base, int dcpu)
{
struct hrtimer *timer;
struct rb_node *node;
@ -1603,6 +1605,18 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
BUG_ON(hrtimer_callback_running(timer));
debug_hrtimer_deactivate(timer);
/*
* Should not happen. Per CPU timers should be
* canceled _before_ the migration code is called
*/
if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU) {
__remove_hrtimer(timer, old_base,
HRTIMER_STATE_INACTIVE, 0);
WARN(1, "hrtimer (%p %p)active but cpu %d dead\n",
timer, timer->function, dcpu);
continue;
}
/*
* Mark it as STATE_MIGRATE not INACTIVE otherwise the
* timer could be seen as !active and just vanish away
@ -1619,12 +1633,11 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
/*
* Happens with high res enabled when the timer was
* already expired and the callback mode is
* HRTIMER_CB_IRQSAFE_NO_SOFTIRQ
* (hrtimer_sleeper). The enqueue code does not move
* them to the soft irq pending list for
* performance/latency reasons, but in the migration
* state, we need to do that otherwise we end up with
* a stale timer.
* HRTIMER_CB_IRQSAFE_UNLOCKED (hrtimer_sleeper). The
* enqueue code does not move them to the soft irq
* pending list for performance/latency reasons, but
* in the migration state, we need to do that
* otherwise we end up with a stale timer.
*/
if (timer->state == HRTIMER_STATE_MIGRATE) {
timer->state = HRTIMER_STATE_PENDING;
@ -1682,7 +1695,7 @@ static void migrate_hrtimers(int cpu)
for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
if (migrate_hrtimer_list(&old_base->clock_base[i],
&new_base->clock_base[i]))
&new_base->clock_base[i], cpu))
raise = 1;
}