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Diffstat (limited to 'kernel/timer.c')
-rw-r--r--kernel/timer.c116
1 files changed, 98 insertions, 18 deletions
diff --git a/kernel/timer.c b/kernel/timer.c
index 9c3c62b0c4bc..a791a43799b0 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;
@@ -653,6 +654,36 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer,
}
}
+#ifndef CONFIG_PREEMPT_RT_FULL
+static inline struct tvec_base *switch_timer_base(struct timer_list *timer,
+ struct tvec_base *old,
+ struct tvec_base *new)
+{
+ /* See the comment in lock_timer_base() */
+ timer_set_base(timer, NULL);
+ spin_unlock(&old->lock);
+ spin_lock(&new->lock);
+ timer_set_base(timer, new);
+ return new;
+}
+#else
+static inline struct tvec_base *switch_timer_base(struct timer_list *timer,
+ struct tvec_base *old,
+ struct tvec_base *new)
+{
+ /*
+ * We cannot do the above because we might be preempted and
+ * then the preempter would see NULL and loop forever.
+ */
+ if (spin_trylock(&new->lock)) {
+ timer_set_base(timer, new);
+ spin_unlock(&old->lock);
+ return new;
+ }
+ return old;
+}
+#endif
+
static inline int
__mod_timer(struct timer_list *timer, unsigned long expires,
bool pending_only, int pinned)
@@ -679,12 +710,15 @@ __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) {
@@ -695,14 +729,8 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
* handler yet has not finished. This also guarantees that
* the timer is serialized wrt itself.
*/
- if (likely(base->running_timer != timer)) {
- /* See the comment in lock_timer_base() */
- timer_set_base(timer, NULL);
- spin_unlock(&base->lock);
- base = new_base;
- spin_lock(&base->lock);
- timer_set_base(timer, base);
- }
+ if (likely(base->running_timer != timer))
+ base = switch_timer_base(timer, base, new_base);
}
timer->expires = expires;
@@ -885,6 +913,29 @@ 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 +1004,7 @@ 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 +1064,7 @@ 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 +1175,11 @@ 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);
}
@@ -1266,6 +1318,23 @@ unsigned long get_next_timer_interrupt(unsigned long now)
*/
if (cpu_is_offline(smp_processor_id()))
return now + NEXT_TIMER_MAX_DELTA;
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+ /*
+ * On PREEMPT_RT we cannot sleep here. If the trylock does not
+ * succeed then we return the worst-case 'expires in 1 tick'
+ * value. We use the rt functions here directly to avoid a
+ * migrate_disable() call.
+ */
+ if (spin_do_trylock(&base->lock)) {
+ if (time_before_eq(base->next_timer, base->timer_jiffies))
+ base->next_timer = __next_timer_interrupt(base);
+ expires = base->next_timer;
+ rt_spin_unlock(&base->lock);
+ } else {
+ expires = now + 1;
+ }
+#else
spin_lock(&base->lock);
if (time_before_eq(base->next_timer, base->timer_jiffies))
base->next_timer = __next_timer_interrupt(base);
@@ -1274,7 +1343,7 @@ unsigned long get_next_timer_interrupt(unsigned long now)
if (time_before_eq(expires, now))
return now;
-
+#endif
return cmp_next_hrtimer_event(now, expires);
}
#endif
@@ -1290,14 +1359,13 @@ void update_process_times(int user_tick)
/* Note: this timer irq context must be accounted for as well. */
account_process_tick(p, user_tick);
+ scheduler_tick();
run_local_timers();
rcu_check_callbacks(cpu, user_tick);
- printk_tick();
-#ifdef CONFIG_IRQ_WORK
+#if defined(CONFIG_IRQ_WORK) && !defined(CONFIG_PREEMPT_RT_FULL)
if (in_irq())
irq_work_run();
#endif
- scheduler_tick();
run_posix_cpu_timers(p);
}
@@ -1308,6 +1376,11 @@ static void run_timer_softirq(struct softirq_action *h)
{
struct tvec_base *base = __this_cpu_read(tvec_bases);
+#if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
+ irq_work_run();
+#endif
+
+ printk_tick();
hrtimer_run_pending();
if (time_after_eq(jiffies, base->timer_jiffies))
@@ -1634,6 +1707,7 @@ 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);
@@ -1669,6 +1743,7 @@ static void __cpuinit migrate_timers(int cpu)
{
struct tvec_base *old_base;
struct tvec_base *new_base;
+ unsigned long flags;
int i;
BUG_ON(cpu_online(cpu));
@@ -1678,8 +1753,11 @@ static void __cpuinit migrate_timers(int cpu)
* The caller is globally serialized and nobody else
* takes two locks at once, deadlock is not possible.
*/
- spin_lock_irq(&new_base->lock);
- spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+ local_irq_save(flags);
+ while (!spin_trylock(&new_base->lock))
+ cpu_relax();
+ while (!spin_trylock(&old_base->lock))
+ cpu_relax();
BUG_ON(old_base->running_timer);
@@ -1693,7 +1771,9 @@ static void __cpuinit migrate_timers(int cpu)
}
spin_unlock(&old_base->lock);
- spin_unlock_irq(&new_base->lock);
+ spin_unlock(&new_base->lock);
+ local_irq_restore(flags);
+
put_cpu_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
generated by cgit v1.2.3 (git 2.0.4) at 2024-12-25 18:25:33 +0000