This patch makes hrtimers initialized with hrtimer_init_sleeper
to use another mode and then not be stuck in waitqueues when
hrtimer_interrupt is very busy.
The new mode is HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFIRQ.
The above-mentionned timers have been moved from
HRTIMER_CB_IRQSAFE_NO_SOFTIRQ to
HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFIRQ.
HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFIRQ timers use a slightly different
state machine from HRTIMER_CB_IRQSAFE_NO_SOFTIRQ's as when removing the
timer, __run_hrtimer sets the status to INACTIVE _then_
wakes up the thread. This way, an awakened thread cannot enter
hrtimer_cancel before the timer's status has changed.
Signed-off-by: Gilles Carry <gilles.carry@xxxxxxxx>
---
include/linux/hrtimer.h | 4 ++++
kernel/hrtimer.c | 26 +++++++++++++++++++++-----
2 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index f3867fd..53f4d44 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -49,12 +49,16 @@ enum hrtimer_restart {
* does not restart the timer
* HRTIMER_CB_IRQSAFE_NO_SOFTIRQ: Callback must run in hardirq context
* Special mode for tick emultation
+ * HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFTIRQ:
+ * Callback must run in hardirq context and
+ * does not restart the timer
*/
enum hrtimer_cb_mode {
HRTIMER_CB_SOFTIRQ,
HRTIMER_CB_IRQSAFE,
HRTIMER_CB_IRQSAFE_NO_RESTART,
HRTIMER_CB_IRQSAFE_NO_SOFTIRQ,
+ HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFTIRQ,
};
/*
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index fa63a24..778eb7e 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -668,6 +668,7 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
/* Timer is expired, act upon the callback mode */
switch(timer->cb_mode) {
case HRTIMER_CB_IRQSAFE_NO_RESTART:
+ case HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFTIRQ:
debug_hrtimer_deactivate(timer);
/*
* We can call the callback from here. No restart
@@ -1089,6 +1090,8 @@ int hrtimer_cancel(struct hrtimer *timer)
if (ret >= 0)
return ret;
+ WARN_ON (timer->cb_mode ==
+ HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFTIRQ);
hrtimer_wait_for_timer(timer);
}
}
@@ -1298,11 +1301,18 @@ static void __run_hrtimer(struct hrtimer *timer)
int restart;
debug_hrtimer_deactivate(timer);
- __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
- timer_stats_account_hrtimer(timer);
fn = timer->function;
- if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {
+
+ switch (timer->cb_mode) {
+ case HRTIMER_CB_IRQSAFE_NO_RESTART_NO_SOFTIRQ:
+ __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
+ timer_stats_account_hrtimer(timer);
+ spin_unlock(&cpu_base->lock);
+ fn(timer);
+ spin_lock(&cpu_base->lock);
+ return;
+ case HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:
/*
* Used for scheduler timers, avoid lock inversion with
* rq->lock and tasklist_lock.
@@ -1310,11 +1320,17 @@ static void __run_hrtimer(struct hrtimer *timer)
* These timers are required to deal with enqueue expiry
* themselves and are not allowed to migrate.
*/
+ __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
+ timer_stats_account_hrtimer(timer);
spin_unlock(&cpu_base->lock);
restart = fn(timer);
spin_lock(&cpu_base->lock);
- } else
+ break;
+ default:
+ __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
+ timer_stats_account_hrtimer(timer);
restart = fn(timer);
+ }
/*
* Note: We clear the CALLBACK bit after enqueue_hrtimer to avoid
@@ -1516,7 +1532,7 @@ 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_NO_RESTART_NO_SOFTIRQ;
#endif
}
--
1.5.2.2
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