[PATCH 2/2] sched_clock: Disable seqlock lockdep usage in sched_clock

From: John Stultz
Date: Thu Jan 02 2014 - 18:11:41 EST

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 HaÅasa <khalasa@xxxxxxx>
Cc: Uwe Kleine-KÃnig <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>,
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Reported-by: Krzysztof HaÅasa <khalasa@xxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
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);

- 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);


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