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| author | Pavel Tatashin <pasha.tatashin@oracle.com> | 2017-03-22 23:24:17 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-03-27 11:23:48 +0300 |
| commit | 7b09cc5a9debc86c903c2eff8f8a1fdef773c649 (patch) | |
| tree | 6e35ca2c34f1ab45e176da65cad9b1e14079ff4d /kernel/sched | |
| parent | 698eff6355f735d46d1b7113df8b422874cd7988 (diff) | |
| download | linux-7b09cc5a9debc86c903c2eff8f8a1fdef773c649.tar.xz | |
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 <pasha.tatashin@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Fixes: 5680d8094ffa ("sched/clock: Provide better clock continuity")
Link: http://lkml.kernel.org/r/1490214265-899964-2-git-send-email-pasha.tatashin@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/clock.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 24a3e01bf8cb..00a45c45beca 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); |