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| author | Aaron Thompson <dev@aaront.org> | 2023-04-13 19:50:12 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-04-21 13:24:21 +0200 |
| commit | f31dcb152a3d0816e2f1deab4e64572336da197d (patch) | |
| tree | b4342c5eb0b490cdb33b75e73a213d5087c1ed17 /kernel/sched/clock.c | |
| parent | sched/rt: Fix bad task migration for rt tasks (diff) | |
| download | linux-f31dcb152a3d0816e2f1deab4e64572336da197d.tar.xz linux-f31dcb152a3d0816e2f1deab4e64572336da197d.zip | |
sched/clock: Fix local_clock() before sched_clock_init()
Have local_clock() return sched_clock() if sched_clock_init() has not
yet run. sched_clock_cpu() has this check but it was not included in the
new noinstr implementation of local_clock().
The effect can be seen on x86 with CONFIG_PRINTK_TIME enabled, for
instance. scd->clock quickly reaches the value of TICK_NSEC and that
value is returned until sched_clock_init() runs.
dmesg without this patch:
[ 0.000000] kvm-clock: ...
[ 0.000002] kvm-clock: ...
[ 0.000672] clocksource: ...
[ 0.001000] tsc: ...
[ 0.001000] e820: ...
[ 0.001000] e820: ...
...
[ 0.001000] ..TIMER: ...
[ 0.001000] clocksource: ...
[ 0.378956] Calibrating delay loop ...
[ 0.379955] pid_max: ...
dmesg with this patch:
[ 0.000000] kvm-clock: ...
[ 0.000001] kvm-clock: ...
[ 0.000675] clocksource: ...
[ 0.002685] tsc: ...
[ 0.003331] e820: ...
[ 0.004190] e820: ...
...
[ 0.421939] ..TIMER: ...
[ 0.422842] clocksource: ...
[ 0.424582] Calibrating delay loop ...
[ 0.425580] pid_max: ...
Fixes: 776f22913b8e ("sched/clock: Make local_clock() noinstr")
Signed-off-by: Aaron Thompson <dev@aaront.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230413175012.2201-1-dev@aaront.org
Diffstat (limited to 'kernel/sched/clock.c')
| -rw-r--r-- | kernel/sched/clock.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 5732fa75ebab..b5cc2b53464d 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -300,6 +300,9 @@ noinstr u64 local_clock(void) if (static_branch_likely(&__sched_clock_stable)) return sched_clock() + __sched_clock_offset; + if (!static_branch_likely(&sched_clock_running)) + return sched_clock(); + preempt_disable_notrace(); clock = sched_clock_local(this_scd()); preempt_enable_notrace(); |