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Fix a PREEMPT_RT bug in the clocksource verification code that

Browse source 
caused false positive warnings.
 
 Also fix a timer migration setup bug when new CPUs are added.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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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
This commit is contained in:
Linus Torvalds 2025-02-08 11:55:03 -08:00
commit 3a0562d733
2 changed files with 13 additions and 3 deletions
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6
kernel/time/clocksource.c
View file

@ -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",

10
kernel/time/timer_migration.c
View file

@ -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