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Fix boot-time warning in tick_setup_device().

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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-urgent-2024-06-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fix from Ingo Molnar:
 "Fix boot-time warning in tick_setup_device()"

* tag 'timers-urgent-2024-06-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick/nohz_full: Don't abuse smp_call_function_single() in tick_setup_device()
This commit is contained in:
Linus Torvalds 2024-06-15 10:54:24 -07:00
commit 41d707222e
1 changed files with 14 additions and 28 deletions
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42
kernel/time/tick-common.c
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@ -178,26 +178,6 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
}
}
#ifdef CONFIG_NO_HZ_FULL
static void giveup_do_timer(void *info)
{
int cpu = *(unsigned int *)info;
WARN_ON(tick_do_timer_cpu != smp_processor_id());
tick_do_timer_cpu = cpu;
}
static void tick_take_do_timer_from_boot(void)
{
int cpu = smp_processor_id();
int from = tick_do_timer_boot_cpu;
if (from >= 0 && from != cpu)
smp_call_function_single(from, giveup_do_timer, &cpu, 1);
}
#endif
/*
* Setup the tick device
*/
@ -221,19 +201,25 @@ static void tick_setup_device(struct tick_device *td,
tick_next_period = ktime_get();
#ifdef CONFIG_NO_HZ_FULL
/*
* The boot CPU may be nohz_full, in which case set
* tick_do_timer_boot_cpu so the first housekeeping
* secondary that comes up will take do_timer from
* us.
* The boot CPU may be nohz_full, in which case the
* first housekeeping secondary will take do_timer()
* from it.
*/
if (tick_nohz_full_cpu(cpu))
tick_do_timer_boot_cpu = cpu;
} else if (tick_do_timer_boot_cpu != -1 &&
!tick_nohz_full_cpu(cpu)) {
tick_take_do_timer_from_boot();
} else if (tick_do_timer_boot_cpu != -1 && !tick_nohz_full_cpu(cpu)) {
tick_do_timer_boot_cpu = -1;
WARN_ON(READ_ONCE(tick_do_timer_cpu) != cpu);
/*
* The boot CPU will stay in periodic (NOHZ disabled)
* mode until clocksource_done_booting() called after
* smp_init() selects a high resolution clocksource and
* timekeeping_notify() kicks the NOHZ stuff alive.
*
* So this WRITE_ONCE can only race with the READ_ONCE
* check in tick_periodic() but this race is harmless.
*/
WRITE_ONCE(tick_do_timer_cpu, cpu);
#endif
}