Commit 41d70722 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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()
parents 44ef20ba 07c54cc5

kernel/time/tick-common.c

+14 −28
Original line number Diff line number Diff line
@@ -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

		}