From: john.stultz@linaro.org (John Stultz)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] sched_clock: Disable seqlock lockdep usage in sched_clock
Date: Thu, 2 Jan 2014 13:54:46 -0800 [thread overview]
Message-ID: <1388699686-4834-1-git-send-email-john.stultz@linaro.org> (raw)
In-Reply-To: <52C5DB5B.9050604@linaro.org>
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 Ha?asa <khalasa@piap.pl>
Cc: Uwe Kleine-K?nig <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 at lists.infradead.org
Reported-by: Krzysztof Ha?asa <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
next prev parent reply other threads:[~2014-01-02 21:54 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-31 10:37 v3.13-rc6+ regression (ARM board) Krzysztof Hałasa
2013-12-31 10:45 ` Willy Tarreau
2014-01-02 10:02 ` Krzysztof Hałasa
2014-01-02 10:14 ` Uwe Kleine-König
2014-01-02 12:07 ` Krzysztof Hałasa
2014-01-02 19:38 ` Linus Torvalds
2014-01-02 20:03 ` John Stultz
2014-01-02 20:30 ` John Stultz
2014-01-02 20:42 ` Stephen Boyd
2014-01-02 20:52 ` John Stultz
2014-01-02 20:43 ` Linus Torvalds
2014-01-02 21:34 ` John Stultz
2014-01-02 21:54 ` John Stultz [this message]
2014-01-02 22:15 ` [PATCH] sched_clock: Disable seqlock lockdep usage in sched_clock Linus Torvalds
2014-01-02 22:21 ` John Stultz
2014-01-02 23:11 ` [PATCH 1/2] seqlock: Use raw_ prefix instead of _no_lockdep John Stultz
2014-01-02 23:11 ` [PATCH 2/2] sched_clock: Disable seqlock lockdep usage in sched_clock John Stultz
2014-01-03 0:46 ` Stephen Boyd
2014-01-03 6:05 ` Krzysztof Hałasa
2014-01-03 0:46 ` [PATCH 1/2] seqlock: Use raw_ prefix instead of _no_lockdep Stephen Boyd
2014-01-03 0:50 ` Linus Torvalds
2014-01-04 0:28 ` John Stultz
2014-01-06 10:10 ` Peter Zijlstra
2014-01-03 6:01 ` v3.13-rc6+ regression (ARM board) Krzysztof Hałasa
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