Commit-ID: 7b09cc5a9debc86c903c2eff8f8a1fdef773c649 Gitweb: http://git.kernel.org/tip/7b09cc5a9debc86c903c2eff8f8a1fdef773c649 Author: Pavel Tatashin <[email protected]> AuthorDate: Wed, 22 Mar 2017 16:24:17 -0400 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 27 Mar 2017 10:23:48 +0200
sched/clock: Fix broken stable to unstable transfer When it is determined that the clock is actually unstable, and we switch from stable to unstable, the __clear_sched_clock_stable() function is eventually called. In this function we set gtod_offset so the following holds true: sched_clock() + raw_offset == ktime_get_ns() + gtod_offset But instead of getting the latest timestamps, we use the last values from scd, so instead of sched_clock() we use scd->tick_raw, and instead of ktime_get_ns() we use scd->tick_gtod. However, later, when we use gtod_offset sched_clock_local() we do not add it to scd->tick_gtod to calculate the correct clock value when we determine the boundaries for min/max clocks. This can result in tick granularity sched_clock() values, so fix it. Signed-off-by: Pavel Tatashin <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Fixes: 5680d8094ffa ("sched/clock: Provide better clock continuity") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/sched/clock.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 24a3e01..00a45c4 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -221,7 +221,7 @@ static inline u64 wrap_max(u64 x, u64 y) */ static u64 sched_clock_local(struct sched_clock_data *scd) { - u64 now, clock, old_clock, min_clock, max_clock; + u64 now, clock, old_clock, min_clock, max_clock, gtod; s64 delta; again: @@ -238,9 +238,10 @@ again: * scd->tick_gtod + TICK_NSEC); */ - clock = scd->tick_gtod + __gtod_offset + delta; - min_clock = wrap_max(scd->tick_gtod, old_clock); - max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC); + gtod = scd->tick_gtod + __gtod_offset; + clock = gtod + delta; + min_clock = wrap_max(gtod, old_clock); + max_clock = wrap_max(old_clock, gtod + TICK_NSEC); clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock);
