diff options
author | Ingo Molnar <mingo@elte.hu> | 2009-07-03 08:29:34 -0500 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2012-07-17 21:15:11 -0400 |
commit | d9934e41c0fb51d0afbfff386b18f9ed48af9123 (patch) | |
tree | f70a4b7e90465db2980c7dc729d5620193e11cef /kernel | |
parent | 4611f846bce43364ec89f9aad4ff2415b82c7caf (diff) |
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/timer.c | 35 |
1 files changed, 32 insertions, 3 deletions
diff --git a/kernel/timer.c b/kernel/timer.c index 9c3c62b0c4bc..e4b237370b93 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -75,6 +75,7 @@ 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; struct tvec_root tv1; @@ -679,12 +680,15 @@ __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) && 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) { @@ -885,6 +889,29 @@ 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 @@ -953,7 +980,7 @@ out: } 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 @@ -1013,7 +1040,7 @@ 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); @@ -1124,10 +1151,11 @@ static inline void __run_timers(struct tvec_base *base) 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); } @@ -1634,6 +1662,7 @@ static int __cpuinit init_timers_cpu(int cpu) } spin_lock_init(&base->lock); + init_waitqueue_head(&base->wait_for_running_timer); for (j = 0; j < TVN_SIZE; j++) { INIT_LIST_HEAD(base->tv5.vec + j); |