Messages in this thread Patch in this message | | | From | Leo Yan <> | Subject | [PATCH v3 2/7] time/sched_clock: Use raw_read_seqcount_latch() | Date | Thu, 16 Jul 2020 13:11:25 +0800 |
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From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
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.
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 References: 1809bfa44e10 ("timers, sched/clock: Avoid deadlock during read from NMI") Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Leo Yan <leo.yan@linaro.org> --- kernel/time/sched_clock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
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); } -- 2.17.1
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