time/sched_clock: Expire timer in hardirq context
[ Upstream commit 2c8bd58812
]
To minimize latency, PREEMPT_RT kernels expires hrtimers in preemptible
softirq context by default. This can be overriden by marking the timer's
expiry with HRTIMER_MODE_HARD.
sched_clock_timer is missing this annotation: if its callback is preempted
and the duration of the preemption exceeds the wrap around time of the
underlying clocksource, sched clock will get out of sync.
Mark the sched_clock_timer for expiry in hard interrupt context.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200309181529.26558-1-a.darwish@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
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@ -207,7 +207,8 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
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if (sched_clock_timer.function != NULL) {
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/* update timeout for clock wrap */
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hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
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hrtimer_start(&sched_clock_timer, cd.wrap_kt,
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HRTIMER_MODE_REL_HARD);
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}
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r = rate;
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@ -251,9 +252,9 @@ void __init generic_sched_clock_init(void)
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* Start the timer to keep sched_clock() properly updated and
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* sets the initial epoch.
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*/
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hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
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sched_clock_timer.function = sched_clock_poll;
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hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
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hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL_HARD);
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}
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/*
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@ -290,7 +291,7 @@ void sched_clock_resume(void)
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struct clock_read_data *rd = &cd.read_data[0];
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rd->epoch_cyc = cd.actual_read_sched_clock();
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hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
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hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL_HARD);
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rd->read_sched_clock = cd.actual_read_sched_clock;
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}
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