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 <t...@linutronix.de>
---
kernel/time/timekeeping.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
Index: linux-3.6/kernel/time/timekeeping.c
===================================================================
--- linux-3.6.orig/kernel/time/timekeeping.c
+++ linux-3.6/kernel/time/timekeeping.c
@@ -1190,7 +1190,6 @@ 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))
@@ -1242,6 +1241,7 @@ 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;
/*
@@ -1256,9 +1256,8 @@ 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);
}
--
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