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-rw-r--r--include/linux/timer.h1
-rw-r--r--kernel/time/timer.c45
2 files changed, 39 insertions, 7 deletions
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 9f8895decb82..37b5e2f74d21 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -203,6 +203,7 @@ extern void add_timer_on(struct timer_list *timer, int cpu);
extern int del_timer(struct timer_list * timer);
extern int mod_timer(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
+extern int timer_reduce(struct timer_list *timer, unsigned long expires);
/*
* The jiffies value which is added to now, when there is no timer
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index fbb1f85327bf..af0b8bae4502 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -929,8 +929,11 @@ static struct timer_base *lock_timer_base(struct timer_list *timer,
}
}
+#define MOD_TIMER_PENDING_ONLY 0x01
+#define MOD_TIMER_REDUCE 0x02
+
static inline int
-__mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
+__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
{
struct timer_base *base, *new_base;
unsigned int idx = UINT_MAX;
@@ -950,7 +953,11 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
* larger granularity than you would get from adding a new
* timer with this expiry.
*/
- if (timer->expires == expires)
+ long diff = timer->expires - expires;
+
+ if (!diff)
+ return 1;
+ if (options & MOD_TIMER_REDUCE && diff <= 0)
return 1;
/*
@@ -962,6 +969,12 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
base = lock_timer_base(timer, &flags);
forward_timer_base(base);
+ if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
+ time_before_eq(timer->expires, expires)) {
+ ret = 1;
+ goto out_unlock;
+ }
+
clk = base->clk;
idx = calc_wheel_index(expires, clk);
@@ -971,7 +984,10 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
* subsequent call will exit in the expires check above.
*/
if (idx == timer_get_idx(timer)) {
- timer->expires = expires;
+ if (!(options & MOD_TIMER_REDUCE))
+ timer->expires = expires;
+ else if (time_after(timer->expires, expires))
+ timer->expires = expires;
ret = 1;
goto out_unlock;
}
@@ -981,7 +997,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
}
ret = detach_if_pending(timer, base, false);
- if (!ret && pending_only)
+ if (!ret && (options & MOD_TIMER_PENDING_ONLY))
goto out_unlock;
debug_activate(timer, expires);
@@ -1042,7 +1058,7 @@ out_unlock:
*/
int mod_timer_pending(struct timer_list *timer, unsigned long expires)
{
- return __mod_timer(timer, expires, true);
+ return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
}
EXPORT_SYMBOL(mod_timer_pending);
@@ -1068,11 +1084,26 @@ EXPORT_SYMBOL(mod_timer_pending);
*/
int mod_timer(struct timer_list *timer, unsigned long expires)
{
- return __mod_timer(timer, expires, false);
+ return __mod_timer(timer, expires, 0);
}
EXPORT_SYMBOL(mod_timer);
/**
+ * timer_reduce - Modify a timer's timeout if it would reduce the timeout
+ * @timer: The timer to be modified
+ * @expires: New timeout in jiffies
+ *
+ * timer_reduce() is very similar to mod_timer(), except that it will only
+ * modify a running timer if that would reduce the expiration time (it will
+ * start a timer that isn't running).
+ */
+int timer_reduce(struct timer_list *timer, unsigned long expires)
+{
+ return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
+}
+EXPORT_SYMBOL(timer_reduce);
+
+/**
* add_timer - start a timer
* @timer: the timer to be added
*
@@ -1754,7 +1785,7 @@ signed long __sched schedule_timeout(signed long timeout)
timer.task = current;
timer_setup_on_stack(&timer.timer, process_timeout, 0);
- __mod_timer(&timer.timer, expire, false);
+ __mod_timer(&timer.timer, expire, 0);
schedule();
del_singleshot_timer_sync(&timer.timer);

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