Commit 3a0562d7 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'timers-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull timer fixes from Ingo Molnar:
 "Fix a PREEMPT_RT bug in the clocksource verification code that caused
  false positive warnings.

  Also fix a timer migration setup bug when new CPUs are added"

* tag 'timers-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timers/migration: Fix off-by-one root mis-connection
  clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context
parents c7b92e89 868c9037

kernel/time/clocksource.c

+4 −2
Original line number Diff line number Diff line
@@ -373,10 +373,10 @@ void clocksource_verify_percpu(struct clocksource *cs) 
	cpumask_clear(&cpus_ahead);

	cpumask_clear(&cpus_behind);

	cpus_read_lock();

	preempt_disable();

	migrate_disable();

	clocksource_verify_choose_cpus();

	if (cpumask_empty(&cpus_chosen)) {

		preempt_enable();

		migrate_enable();

		cpus_read_unlock();

		pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);

		return;
@@ -384,6 +384,7 @@ void clocksource_verify_percpu(struct clocksource *cs) 
	testcpu = smp_processor_id();

	pr_info("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n",

		cs->name, testcpu, cpumask_pr_args(&cpus_chosen));

	preempt_disable();

	for_each_cpu(cpu, &cpus_chosen) {

		if (cpu == testcpu)

			continue;
@@ -403,6 +404,7 @@ void clocksource_verify_percpu(struct clocksource *cs) 
			cs_nsec_min = cs_nsec;

	}

	preempt_enable();

	migrate_enable();

	cpus_read_unlock();

	if (!cpumask_empty(&cpus_ahead))

		pr_warn("        CPUs %*pbl ahead of CPU %d for clocksource %s.\n",

kernel/time/timer_migration.c

+9 −1
Original line number Diff line number Diff line
@@ -1675,6 +1675,9 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node) 


	} while (i < tmigr_hierarchy_levels);



	/* Assert single root */

	WARN_ON_ONCE(!err && !group->parent && !list_is_singular(&tmigr_level_list[top]));



	while (i > 0) {

		group = stack[--i];
@@ -1716,7 +1719,12 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node) 
		WARN_ON_ONCE(top == 0);



		lvllist = &tmigr_level_list[top];

		if (group->num_children == 1 && list_is_singular(lvllist)) {



		/*

		 * Newly created root level should have accounted the upcoming

		 * CPU's child group and pre-accounted the old root.

		 */

		if (group->num_children == 2 && list_is_singular(lvllist)) {

			/*

			 * The target CPU must never do the prepare work, except

			 * on early boot when the boot CPU is the target. Otherwise