timer: Make try_to_del_timer_sync() the same on SMP and UP

On UP try_to_del_timer_sync() is mapped to del_timer() which does not
take the running timer callback into account, so it has different
semantics.

Remove the SMP dependency of try_to_del_timer_sync() by using
base->running_timer in the UP case as well.

[ tglx: Removed set_running_timer() inline and tweaked the changelog ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 5 insertions, 16 deletions

diff --git a/include/linux/timer.h b/include/linux/timer.h
index cbfb7a355d30..6abd9138beda 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -274,11 +274,11 @@ static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
 
 extern void add_timer(struct timer_list *timer);
 
+extern int try_to_del_timer_sync(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 try_to_del_timer_sync(t)       del_timer(t)
 # define del_timer_sync(t)              del_timer(t)
 #endif
 
diff --git a/kernel/timer.c b/kernel/timer.c
index 72853b256ff2..47b86c1e3226 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -330,15 +330,6 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
 }
 EXPORT_SYMBOL_GPL(set_timer_slack);
 
-
-static inline void set_running_timer(struct tvec_base *base,
-                                        struct timer_list *timer)
-{
-#ifdef CONFIG_SMP
-        base->running_timer = timer;
-#endif
-}
-
 static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
         unsigned long expires = timer->expires;
@@ -923,15 +914,12 @@ int del_timer(struct timer_list *timer)
 }
 EXPORT_SYMBOL(del_timer);
 
-#ifdef CONFIG_SMP
 /**
  * try_to_del_timer_sync - Try to deactivate a timer
  * @timer: timer do del
  *
  * 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)
 {
@@ -960,6 +948,7 @@ out:
 }
 EXPORT_SYMBOL(try_to_del_timer_sync);
 
+#ifdef CONFIG_SMP
 /**
  * del_timer_sync - deactivate a timer and wait for the handler to finish.
  * @timer: the timer to be deactivated
@@ -1098,7 +1087,7 @@ static inline void __run_timers(struct tvec_base *base)
 
                         timer_stats_account_timer(timer);
 
-                        set_running_timer(base, timer);
+                        base->running_timer = timer;
                         detach_timer(timer, 1);
 
                         spin_unlock_irq(&base->lock);
@@ -1106,7 +1095,7 @@ static inline void __run_timers(struct tvec_base *base)
                         spin_lock_irq(&base->lock);
                 }
         }
-        set_running_timer(base, NULL);
+        base->running_timer = NULL;
         spin_unlock_irq(&base->lock);
 }