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Commit ca4523cd authored by Thomas Gleixner's avatar Thomas Gleixner Committed by John Stultz
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timekeeping: Shorten seq_count region 



Shorten the seqcount write hold region to the actual update of the
timekeeper and the related data (e.g vsyscall).

On a contemporary x86 system this reduces the maximum latencies on
Preempt-RT from 8us to 4us on the non-timekeeping cores.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 48cdc135

kernel/time/timekeeping.c

+2 −3
Original line number Diff line number Diff line
@@ -1341,7 +1341,6 @@ static void update_wall_time(void) 
	unsigned long flags;



	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	/* Make sure we're fully resumed: */

	if (unlikely(timekeeping_suspended))
@@ -1393,6 +1392,7 @@ static void update_wall_time(void) 
	 */

	accumulate_nsecs_to_secs(tk);



	write_seqcount_begin(&timekeeper_seq);

	/* Update clock->cycle_last with the new value */

	clock->cycle_last = tk->cycle_last;

	/*
@@ -1407,9 +1407,8 @@ static void update_wall_time(void) 
	 */

	memcpy(real_tk, tk, sizeof(*tk));

	timekeeping_update(real_tk, false, false);



out:

	write_seqcount_end(&timekeeper_seq);

out:

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

}