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authorThomas Gleixner <tglx@linutronix.de>2008-09-29 15:47:42 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-09-29 17:09:14 +0200
commitccc7dadf736639da86f3e0c86832c11a66fc8221 (patch)
tree3f1c0df0a291fec4a10d72cc1ab278ad81e697c5 /kernel/hrtimer.c
parentb00c1a99e7758f794923c61e5cd55268d61c9469 (diff)
hrtimer: prevent migration of per CPU hrtimers
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>
Diffstat (limited to 'kernel/hrtimer.c')
-rw-r--r--kernel/hrtimer.c37
1 files changed, 25 insertions, 12 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ace723dd1e52..cdec83e722fa 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -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;
@@ -1604,6 +1606,18 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
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
* under us on another CPU
@@ -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;
}