timers: Consider slack value in mod_timer() (1c3cc116) · Commits · 戴 / test

There is an optimization which does not update the timer if the timer was pending and the expiration time was unchanged. Since commit ("timers: Introduce the concept of timer slack for legacy timers") this optimization is no longer applied for timers where the expiration time got extended due to the slack value. So we need to check again after the expiration time might have been updated. [ tglx: Made it a single check by applying slack first and sorting out the slack = 0 value (all timeouts < 256 jiffies) early ] Signed-off-by:

Sebastian Andrzej Siewior <sebastian@breakpoint.cc> Link: http://lkml.kernel.org/r/20110521105828.GA29442@Chamillionaire.breakpoint.cc Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

kernel/timer.c

+7 −8

Original line number	Diff line number	Diff line
		@@ -749,16 +749,15 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
		unsigned long expires_limit, mask;
		int bit;

		expires_limit = expires;

		if (timer->slack >= 0) {
		expires_limit = expires + timer->slack;
		} else {
		unsigned long now = jiffies;
		long delta = expires - jiffies;

		if (delta < 256)
		return expires;

		/* No slack, if already expired else auto slack 0.4% */
		if (time_after(expires, now))
		expires_limit = expires + (expires - now)/256;
		expires_limit = expires + delta / 256;
		}
		mask = expires ^ expires_limit;
		if (mask == 0)
		@@ -795,6 +794,8 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
		*/
		int mod_timer(struct timer_list *timer, unsigned long expires)
		{
		expires = apply_slack(timer, expires);

		/*
		* This is a common optimization triggered by the
		* networking code - if the timer is re-modified
		@@ -803,8 +804,6 @@ int mod_timer(struct timer_list *timer, unsigned long expires)
		if (timer_pending(timer) && timer->expires == expires)
		return 1;

		expires = apply_slack(timer, expires);

		return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
		}
		EXPORT_SYMBOL(mod_timer);

Admin message