Commit 7a06c41c authored Jan 02, 2014 by John Stultz Committed by Ingo Molnar Jan 12, 2014

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@linux-foundation.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Reported-by: Krzysztof Hałasa <khalasa@piap.pl>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1388704274-5278-2-git-send-email-john.stultz@linaro.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 0c3351d4

kernel/time/sched_clock.c

+3 −3

Original line number	Original line	Diff line number	Diff line
	@@ -74,7 +74,7 @@ unsigned long long notrace sched_clock(void)
	return cd.epoch_ns;		return cd.epoch_ns;

	do {		do {
	seq = read_seqcount_begin(&cd.seq);		seq = raw_read_seqcount_begin(&cd.seq);
	epoch_cyc = cd.epoch_cyc;		epoch_cyc = cd.epoch_cyc;
	epoch_ns = cd.epoch_ns;		epoch_ns = cd.epoch_ns;
	} while (read_seqcount_retry(&cd.seq, seq));		} while (read_seqcount_retry(&cd.seq, seq));
	@@ -99,10 +99,10 @@ static void notrace update_sched_clock(void)
	cd.mult, cd.shift);		cd.mult, cd.shift);

	raw_local_irq_save(flags);		raw_local_irq_save(flags);
	write_seqcount_begin(&cd.seq);		raw_write_seqcount_begin(&cd.seq);
	cd.epoch_ns = ns;		cd.epoch_ns = ns;
	cd.epoch_cyc = cyc;		cd.epoch_cyc = cyc;
	write_seqcount_end(&cd.seq);		raw_write_seqcount_end(&cd.seq);
	raw_local_irq_restore(flags);		raw_local_irq_restore(flags);
	}		}