linux-kernel - [tip:core/urgent] sched_clock: Disable seqlock lockdep usage in sched

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Date:	Sun, 12 Jan 2014 10:42:38 -0800
From:	tip-bot for John Stultz <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	sboyd@...eaurora.org, john.stultz@...aro.org, w@....eu,
	khalasa@...p.pl, tglx@...utronix.de, u.kleine-koenig@...gutronix.de
Subject: [tip:core/urgent] sched_clock:
  Disable seqlock lockdep usage in sched_clock()

Commit-ID:  7a06c41cbec33c6dbe7eec575c61986122617408
Gitweb:     http://git.kernel.org/tip/7a06c41cbec33c6dbe7eec575c61986122617408
Author:     John Stultz <john.stultz@...aro.org>
AuthorDate: Thu, 2 Jan 2014 15:11:14 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 12 Jan 2014 10:14:00 +0100

sched_clock: Disable seqlock lockdep usage in sched_clock()

Unfortunately the seqlock lockdep enablement can't be used
in sched_clock(), since the lockdep infrastructure eventually
calls into sched_clock(), which causes a deadlock.

Thus, this patch changes all generic sched_clock() usage
to use the raw_* methods.

Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>
Reported-by: Krzysztof Hałasa <khalasa@...p.pl>
Signed-off-by: John Stultz <john.stultz@...aro.org>
Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Willy Tarreau <w@....eu>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1388704274-5278-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/time/sched_clock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index 68b7993..0abb364 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -74,7 +74,7 @@ unsigned long long notrace sched_clock(void)
 		return cd.epoch_ns;
 
 	do {
-		seq = read_seqcount_begin(&cd.seq);
+		seq = raw_read_seqcount_begin(&cd.seq);
 		epoch_cyc = cd.epoch_cyc;
 		epoch_ns = cd.epoch_ns;
 	} while (read_seqcount_retry(&cd.seq, seq));
@@ -99,10 +99,10 @@ static void notrace update_sched_clock(void)
 			  cd.mult, cd.shift);
 
 	raw_local_irq_save(flags);
-	write_seqcount_begin(&cd.seq);
+	raw_write_seqcount_begin(&cd.seq);
 	cd.epoch_ns = ns;
 	cd.epoch_cyc = cyc;
-	write_seqcount_end(&cd.seq);
+	raw_write_seqcount_end(&cd.seq);
 	raw_local_irq_restore(flags);
 }
 
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