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| author |   Ahmed S. Darwish <a.darwish@linutronix.de> | 2020-07-16 13:11:25 +0800 |
|---|---|---|
| committer |   Will Deacon <will@kernel.org> | 2020-07-20 11:50:47 +0100 |
| commit | aadd6e5caaacd6feca9691ba30536e7de5a7d152 (patch) | |
| tree | f787a5427d498335af8c1abbb1b1ff3091f18624 /kernel/time | |
| parent | sched_clock: Expose struct clock_read_data (diff) | |
| download | linux-dev-aadd6e5caaacd6feca9691ba30536e7de5a7d152.tar.xz linux-dev-aadd6e5caaacd6feca9691ba30536e7de5a7d152.zip | |
time/sched_clock: Use raw_read_seqcount_latch()
sched_clock uses seqcount_t latching to switch between two storage
places protected by the sequence counter. This allows it to have
interruptible, NMI-safe, seqcount_t write side critical sections.
Since 7fc26327b756 ("seqlock: Introduce raw_read_seqcount_latch()"),
raw_read_seqcount_latch() became the standardized way for seqcount_t
latch read paths. Due to the dependent load, it also has one read
memory barrier less than the currently used raw_read_seqcount() API.
Use raw_read_seqcount_latch() for the seqcount_t latch read path.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lkml.kernel.org/r/20200625085745.GD117543@hirez.programming.kicks-ass.net
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
Link: https://lore.kernel.org/r/20200716051130.4359-3-leo.yan@linaro.org
References: 1809bfa44e10 ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/sched_clock.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index 0acaadc3156c..0deaf4b79fb4 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -70,7 +70,7 @@ static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift) struct clock_read_data *sched_clock_read_begin(unsigned int *seq) { - *seq = raw_read_seqcount(&cd.seq); + *seq = raw_read_seqcount_latch(&cd.seq); return cd.read_data + (*seq & 1); } |