From 58faf20a086bd34f91983609e26eac3d5fe76be3 Mon Sep 17 00:00:00 2001 From: "Ahmed S. Darwish" Date: Thu, 27 Aug 2020 13:40:37 +0200 Subject: time/sched_clock: Use raw_read_seqcount_latch() during suspend 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 has one read memory barrier less than the currently used raw_read_seqcount() API. Use raw_read_seqcount_latch() for the suspend path. Commit aadd6e5caaac ("time/sched_clock: Use raw_read_seqcount_latch()") missed changing that instance of raw_read_seqcount(). References: 1809bfa44e10 ("timers, sched/clock: Avoid deadlock during read from NMI") Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de --- 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 1c03eec6ca9b..8c6b5febd7a0 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -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; } -- cgit v1.2.3