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tick/nohz_full: Don't abuse smp_call_function_single() in tick_setup_device()

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After the recent commit 5097cbcb38 ("sched/isolation: Prevent boot crash
when the boot CPU is nohz_full") the kernel no longer crashes, but there is
another problem.

In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
in smp_call_function_single().

Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
comment explains why this is safe (thanks Thomas!).

Fixes: 08ae95f4fd ("nohz_full: Allow the boot CPU to be nohz_full")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com
This commit is contained in:
Oleg Nesterov 2024-05-28 14:20:19 +02:00 committed by Thomas Gleixner
parent 83a7eefedc
commit 07c54cc598
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 * Setup the tick device
*/ */
@ -221,19 +201,25 @@ static void tick_setup_device(struct tick_device *td,
tick_next_period = ktime_get(); tick_next_period = ktime_get();
#ifdef CONFIG_NO_HZ_FULL #ifdef CONFIG_NO_HZ_FULL
/* /*
* The boot CPU may be nohz_full, in which case set * The boot CPU may be nohz_full, in which case the
* tick_do_timer_boot_cpu so the first housekeeping * first housekeeping secondary will take do_timer()
* secondary that comes up will take do_timer from * from it.
* us.
*/ */
if (tick_nohz_full_cpu(cpu)) if (tick_nohz_full_cpu(cpu))
tick_do_timer_boot_cpu = cpu; tick_do_timer_boot_cpu = cpu;
} else if (tick_do_timer_boot_cpu != -1 && } else if (tick_do_timer_boot_cpu != -1 && !tick_nohz_full_cpu(cpu)) {
!tick_nohz_full_cpu(cpu)) {
tick_take_do_timer_from_boot();
tick_do_timer_boot_cpu = -1; 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 #endif
} }