Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH] sched_clock: Disable seqlock lockdep usage in sched_clock | Date | Thu, 2 Jan 2014 13:54:46 -0800 |
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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 adds _no_lockdep() seqlock methods for the writer side, and changes all generic sched_clock usage to use the _no_lockdep methods.
This solves the issue I was able to reproduce, but it would be good to get Krzysztof to confirm it solves his problem.
Cc: Krzysztof Hałasa <khalasa@piap.pl> Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: Willy Tarreau <w@1wt.eu> Cc: Ingo Molnar <mingo@kernel.org>, Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Boyd <sboyd@codeaurora.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-arm-kernel@lists.infradead.org Reported-by: Krzysztof Hałasa <khalasa@piap.pl> Signed-off-by: John Stultz <john.stultz@linaro.org> --- include/linux/seqlock.h | 19 +++++++++++++++---- kernel/time/sched_clock.c | 6 +++--- 2 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index cf87a24..7664f68 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -206,14 +206,26 @@ static inline int read_seqcount_retry(const seqcount_t *s, unsigned start) } + +static inline void write_seqcount_begin_no_lockdep(seqcount_t *s) +{ + s->sequence++; + smp_wmb(); +} + +static inline void write_seqcount_end_no_lockdep(seqcount_t *s) +{ + smp_wmb(); + s->sequence++; +} + /* * Sequence counter only version assumes that callers are using their * own mutexing. */ static inline void write_seqcount_begin_nested(seqcount_t *s, int subclass) { - s->sequence++; - smp_wmb(); + write_seqcount_begin_no_lockdep(s); seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_); } @@ -225,8 +237,7 @@ static inline void write_seqcount_begin(seqcount_t *s) static inline void write_seqcount_end(seqcount_t *s) { seqcount_release(&s->dep_map, 1, _RET_IP_); - smp_wmb(); - s->sequence++; + write_seqcount_end_no_lockdep(s); } /** diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index 68b7993..13561a0 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 = read_seqcount_begin_no_lockdep(&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); + write_seqcount_begin_no_lockdep(&cd.seq); cd.epoch_ns = ns; cd.epoch_cyc = cyc; - write_seqcount_end(&cd.seq); + write_seqcount_end_no_lockdep(&cd.seq); raw_local_irq_restore(flags); } -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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