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time/sched_clock: Use raw_read_seqcount_latch() during suspend

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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 7fc26327b7 ("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 has one read memory
barrier less than the currently used raw_read_seqcount() API.

Use raw_read_seqcount_latch() for the suspend path.

Commit aadd6e5caa ("time/sched_clock: Use raw_read_seqcount_latch()")
missed changing that instance of raw_read_seqcount().

References: 1809bfa44e ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
This commit is contained in:
Ahmed S. Darwish 2020-08-27 13:40:37 +02:00 committed by Peter Zijlstra
parent 96a16f45ae
commit 58faf20a08
1 changed files with 1 additions and 1 deletions
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2
kernel/time/sched_clock.c
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@ -258,7 +258,7 @@ void __init generic_sched_clock_init(void)
*/
static u64 notrace suspended_sched_clock_read(void)
{
unsigned int seq = raw_read_seqcount(&cd.seq);
unsigned int seq = raw_read_seqcount_latch(&cd.seq);
return cd.read_data[seq & 1].epoch_cyc;
}