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tick/nohz_full: Don't abuse smp_call_function_single() in tick_setup_device()
After the recent commit5097cbcb38
("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
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parent
83a7eefedc
commit
07c54cc598
@ -178,26 +178,6 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
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}
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}
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#ifdef CONFIG_NO_HZ_FULL
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static void giveup_do_timer(void *info)
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{
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int cpu = *(unsigned int *)info;
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WARN_ON(tick_do_timer_cpu != smp_processor_id());
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tick_do_timer_cpu = cpu;
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}
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static void tick_take_do_timer_from_boot(void)
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{
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int cpu = smp_processor_id();
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int from = tick_do_timer_boot_cpu;
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if (from >= 0 && from != cpu)
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smp_call_function_single(from, giveup_do_timer, &cpu, 1);
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}
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#endif
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/*
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* Setup the tick device
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*/
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@ -221,19 +201,25 @@ static void tick_setup_device(struct tick_device *td,
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tick_next_period = ktime_get();
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#ifdef CONFIG_NO_HZ_FULL
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/*
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* The boot CPU may be nohz_full, in which case set
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* tick_do_timer_boot_cpu so the first housekeeping
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* secondary that comes up will take do_timer from
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* us.
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* The boot CPU may be nohz_full, in which case the
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* first housekeeping secondary will take do_timer()
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* from it.
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*/
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if (tick_nohz_full_cpu(cpu))
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tick_do_timer_boot_cpu = cpu;
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} else if (tick_do_timer_boot_cpu != -1 &&
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!tick_nohz_full_cpu(cpu)) {
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tick_take_do_timer_from_boot();
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} else if (tick_do_timer_boot_cpu != -1 && !tick_nohz_full_cpu(cpu)) {
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tick_do_timer_boot_cpu = -1;
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WARN_ON(READ_ONCE(tick_do_timer_cpu) != cpu);
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/*
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* The boot CPU will stay in periodic (NOHZ disabled)
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* mode until clocksource_done_booting() called after
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* smp_init() selects a high resolution clocksource and
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* timekeeping_notify() kicks the NOHZ stuff alive.
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*
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* So this WRITE_ONCE can only race with the READ_ONCE
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* check in tick_periodic() but this race is harmless.
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*/
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WRITE_ONCE(tick_do_timer_cpu, cpu);
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#endif
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}
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