diff options
author | Ingo Molnar <mingo@elte.hu> | 2009-07-03 13:29:34 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2014-04-10 00:19:05 (GMT) |
commit | 5062db1dd6a5720edb3b310f6c89474b96853c6c (patch) | |
tree | e2a97746a7d3e995fb4d92d43e3b4222fd38dd04 | |
parent | 6ab20341d88df6610a0d2cb02cba3c8a7746d9b8 (diff) | |
download | linux-fsl-qoriq-5062db1dd6a5720edb3b310f6c89474b96853c6c.tar.xz |
timers: prepare for full preemption
When softirqs can be preempted we need to make sure that cancelling
the timer from the active thread can not deadlock vs. a running timer
callback. Add a waitqueue to resolve that.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r-- | include/linux/timer.h | 2 | ||||
-rw-r--r-- | kernel/timer.c | 36 |
2 files changed, 34 insertions, 4 deletions
diff --git a/include/linux/timer.h b/include/linux/timer.h index 8c5a197..5fcd72c 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -241,7 +241,7 @@ extern void add_timer(struct timer_list *timer); extern int try_to_del_timer_sync(struct timer_list *timer); -#ifdef CONFIG_SMP +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL) extern int del_timer_sync(struct timer_list *timer); #else # define del_timer_sync(t) del_timer(t) diff --git a/kernel/timer.c b/kernel/timer.c index 4296d13..cd92037 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -78,6 +78,7 @@ struct tvec_root { struct tvec_base { spinlock_t lock; struct timer_list *running_timer; + wait_queue_head_t wait_for_running_timer; unsigned long timer_jiffies; unsigned long next_timer; unsigned long active_timers; @@ -739,12 +740,15 @@ __mod_timer(struct timer_list *timer, unsigned long expires, debug_activate(timer, expires); + preempt_disable_rt(); cpu = smp_processor_id(); #if defined(CONFIG_NO_HZ_COMMON) && defined(CONFIG_SMP) if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) cpu = get_nohz_timer_target(); #endif + preempt_enable_rt(); + new_base = per_cpu(tvec_bases, cpu); if (base != new_base) { @@ -945,6 +949,29 @@ void add_timer_on(struct timer_list *timer, int cpu) } EXPORT_SYMBOL_GPL(add_timer_on); +#ifdef CONFIG_PREEMPT_RT_FULL +/* + * Wait for a running timer + */ +static void wait_for_running_timer(struct timer_list *timer) +{ + struct tvec_base *base = timer->base; + + if (base->running_timer == timer) + wait_event(base->wait_for_running_timer, + base->running_timer != timer); +} + +# define wakeup_timer_waiters(b) wake_up(&(b)->wait_for_tunning_timer) +#else +static inline void wait_for_running_timer(struct timer_list *timer) +{ + cpu_relax(); +} + +# define wakeup_timer_waiters(b) do { } while (0) +#endif + /** * del_timer - deactive a timer. * @timer: the timer to be deactivated @@ -1002,7 +1029,7 @@ int try_to_del_timer_sync(struct timer_list *timer) } EXPORT_SYMBOL(try_to_del_timer_sync); -#ifdef CONFIG_SMP +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL) /** * del_timer_sync - deactivate a timer and wait for the handler to finish. * @timer: the timer to be deactivated @@ -1062,7 +1089,7 @@ int del_timer_sync(struct timer_list *timer) int ret = try_to_del_timer_sync(timer); if (ret >= 0) return ret; - cpu_relax(); + wait_for_running_timer(timer); } } EXPORT_SYMBOL(del_timer_sync); @@ -1179,15 +1206,17 @@ static inline void __run_timers(struct tvec_base *base) if (irqsafe) { spin_unlock(&base->lock); call_timer_fn(timer, fn, data); + base->running_timer = NULL; spin_lock(&base->lock); } else { spin_unlock_irq(&base->lock); call_timer_fn(timer, fn, data); + base->running_timer = NULL; spin_lock_irq(&base->lock); } } } - base->running_timer = NULL; + wake_up(&base->wait_for_running_timer); spin_unlock_irq(&base->lock); } @@ -1547,6 +1576,7 @@ static int init_timers_cpu(int cpu) base = per_cpu(tvec_bases, cpu); } + init_waitqueue_head(&base->wait_for_running_timer); for (j = 0; j < TVN_SIZE; j++) { INIT_LIST_HEAD(base->tv5.vec + j); |