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>
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@ -1341,7 +1341,6 @@ static void update_wall_time(void)
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unsigned long flags;
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raw_spin_lock_irqsave(&timekeeper_lock, flags);
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write_seqcount_begin(&timekeeper_seq);
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/* Make sure we're fully resumed: */
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if (unlikely(timekeeping_suspended))
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@ -1393,6 +1392,7 @@ static void update_wall_time(void)
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*/
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accumulate_nsecs_to_secs(tk);
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write_seqcount_begin(&timekeeper_seq);
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/* Update clock->cycle_last with the new value */
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clock->cycle_last = tk->cycle_last;
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/*
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@ -1407,9 +1407,8 @@ static void update_wall_time(void)
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*/
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memcpy(real_tk, tk, sizeof(*tk));
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timekeeping_update(real_tk, false, false);
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out:
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write_seqcount_end(&timekeeper_seq);
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out:
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raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
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}
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