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authorOleg Nesterov <oleg@tv-sign.ru>2005-06-23 00:08:59 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 09:45:16 -0700
commitfd450b7318b75343fd76b3d95416853e34e72c95 (patch)
treee747348f7d3c9f1615963dde4f2c8baaf842415f
parent55c888d6d09a0df236adfaf8ccf06ff5d0646775 (diff)
[PATCH] timers: introduce try_to_del_timer_sync()
This patch splits del_timer_sync() into 2 functions. The new one, try_to_del_timer_sync(), returns -1 when it hits executing timer. It can be used in interrupt context, or when the caller hold locks which can prevent completion of the timer's handler. NOTE. Currently it can't be used in interrupt context in UP case, because ->running_timer is used only with CONFIG_SMP. Should the need arise, it is possible to kill #ifdef CONFIG_SMP in set_running_timer(), it is cheap. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/linux/timer.h4
-rw-r--r--kernel/timer.c53
2 files changed, 36 insertions, 21 deletions
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 2e78fedfc06..221f81ac200 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -76,9 +76,11 @@ static inline void add_timer(struct timer_list * timer)
}
#ifdef CONFIG_SMP
+ extern int try_to_del_timer_sync(struct timer_list *timer);
extern int del_timer_sync(struct timer_list *timer);
#else
-# define del_timer_sync(t) del_timer(t)
+# define try_to_del_timer_sync(t) del_timer(t)
+# define del_timer_sync(t) del_timer(t)
#endif
#define del_singleshot_timer_sync(t) del_timer_sync(t)
diff --git a/kernel/timer.c b/kernel/timer.c
index 8aadc62efd6..1f986c16d89 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -365,6 +365,34 @@ int del_timer(struct timer_list *timer)
EXPORT_SYMBOL(del_timer);
#ifdef CONFIG_SMP
+/*
+ * This function tries to deactivate a timer. Upon successful (ret >= 0)
+ * exit the timer is not queued and the handler is not running on any CPU.
+ *
+ * It must not be called from interrupt contexts.
+ */
+int try_to_del_timer_sync(struct timer_list *timer)
+{
+ timer_base_t *base;
+ unsigned long flags;
+ int ret = -1;
+
+ base = lock_timer_base(timer, &flags);
+
+ if (base->running_timer == timer)
+ goto out;
+
+ ret = 0;
+ if (timer_pending(timer)) {
+ detach_timer(timer, 1);
+ ret = 1;
+ }
+out:
+ spin_unlock_irqrestore(&base->lock, flags);
+
+ return ret;
+}
+
/***
* del_timer_sync - deactivate a timer and wait for the handler to finish.
* @timer: the timer to be deactivated
@@ -384,28 +412,13 @@ EXPORT_SYMBOL(del_timer);
*/
int del_timer_sync(struct timer_list *timer)
{
- timer_base_t *base;
- unsigned long flags;
- int ret = -1;
-
check_timer(timer);
- do {
- base = lock_timer_base(timer, &flags);
-
- if (base->running_timer == timer)
- goto unlock;
-
- ret = 0;
- if (timer_pending(timer)) {
- detach_timer(timer, 1);
- ret = 1;
- }
-unlock:
- spin_unlock_irqrestore(&base->lock, flags);
- } while (ret < 0);
-
- return ret;
+ for (;;) {
+ int ret = try_to_del_timer_sync(timer);
+ if (ret >= 0)
+ return ret;
+ }
}
EXPORT_SYMBOL(del_timer_sync);