From ca4523cda429712fc135c5db50920d90eb776a6c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner <tglx@linutronix.de> Date: Thu, 21 Feb 2013 22:51:40 +0000 Subject: [PATCH] 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: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: John Stultz <john.stultz@linaro.org> --- kernel/time/timekeeping.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index d20ffdad62e8..c4d2a8751f3e 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -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); }