linux-kernel - [PATCH 2/2] sched_clock: Disable seqlock lockdep usage in sched

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Message-Id: <1388704274-5278-2-git-send-email-john.stultz@linaro.org>
Date:	Thu,  2 Jan 2014 15:11:14 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Krzysztof Hałasa <khalasa@...p.pl>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Willy Tarreau <w@....eu>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 2/2] sched_clock: Disable seqlock lockdep usage in sched_clock

Unforunately the seqlock lockdep enablmenet 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.

Cc: Krzysztof Hałasa <khalasa@...p.pl>
Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Willy Tarreau <w@....eu>
Cc: Ingo Molnar <mingo@...nel.org>,
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephen Boyd <sboyd@...eaurora.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-arm-kernel@...ts.infradead.org
Reported-by: Krzysztof Hałasa <khalasa@...p.pl>
Signed-off-by: John Stultz <john.stultz@...aro.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);
 }
 
-- 
1.8.3.2

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