linux-kernel - [PATCH 6/9] time: Reduce timekeeper read lock hold time

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Message-Id: <1330672368-32290-7-git-send-email-john.stultz@linaro.org>
Date:	Thu,  1 Mar 2012 23:12:45 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Richard Cochran <richardcochran@...il.com>
Subject: [PATCH 6/9] time: Reduce timekeeper read lock hold time

Now that timekeeper updates are done with a shadow copy,
we can reduce the readlock hold time to only the update.

CC: Ingo Molnar <mingo@...e.hu>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Eric Dumazet <eric.dumazet@...il.com>
CC: Richard Cochran <richardcochran@...il.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 kernel/time/timekeeping.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ed8cb51..97982b1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1071,7 +1071,6 @@ static void update_wall_time(void)
 	s64 remainder;
 
 	spin_lock_irqsave(&timekeeper_wlock, flags);
-	write_seqcount_begin(&timekeeper_rlock);
 
 	/* Make sure we're fully resumed: */
 	if (unlikely(timekeeping_suspended))
@@ -1155,13 +1154,13 @@ static void update_wall_time(void)
 		second_overflow();
 	}
 
-
+	write_seqcount_begin(&timekeeper_rlock);
 	timekeeper = shadow_tk;
 	timekeeper.clock->cycle_last = timekeeper.cycle_last;
 	timekeeping_update(&timekeeper, false);
+	write_seqcount_end(&timekeeper_rlock);
 
 out:
-	write_seqcount_end(&timekeeper_rlock);
 	spin_unlock_irqrestore(&timekeeper_wlock, flags);
 
 }
-- 
1.7.3.2.146.gca209

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