Le Fri, Jul 19, 2024 at 06:06:12PM -0000, tip-bot2 for Anna-Maria Behnsen a écrit :
> @@ -1661,80 +1728,39 @@ static int tmigr_add_cpu(unsigned int cpu)
> return ret;
> }
>
> -static int tmigr_cpu_online(unsigned int cpu)
> -{
> - struct tmigr_cpu *tmc = this_cpu_ptr(&tmigr_cpu);
> - int ret;
> -
> - /* First online attempt? Initialize CPU data */
> - if (!tmc->tmgroup) {
> - raw_spin_lock_init(&tmc->lock);
> -
> - ret = tmigr_add_cpu(cpu);
> - if (ret < 0)
> - return ret;
> -
> - if (tmc->childmask == 0)
> - return -EINVAL;
> -
> - timerqueue_init(&tmc->cpuevt.nextevt);
> - tmc->cpuevt.nextevt.expires = KTIME_MAX;
> - tmc->cpuevt.ignore = true;
> - tmc->cpuevt.cpu = cpu;
> -
> - tmc->remote = false;
> - WRITE_ONCE(tmc->wakeup, KTIME_MAX);
> - }
> - raw_spin_lock_irq(&tmc->lock);
> - trace_tmigr_cpu_online(tmc);
> - tmc->idle = timer_base_is_idle();
> - if (!tmc->idle)
> - __tmigr_cpu_activate(tmc);
> - tmc->online = true;
> - raw_spin_unlock_irq(&tmc->lock);
> - return 0;
> -}
> -
> -/*
> - * tmigr_trigger_active() - trigger a CPU to become active again
> - *
> - * This function is executed on a CPU which is part of cpu_online_mask, when the
> - * last active CPU in the hierarchy is offlining. With this, it is ensured that
> - * the other CPU is active and takes over the migrator duty.
> - */
> -static long tmigr_trigger_active(void *unused)
> +static int tmigr_cpu_prepare(unsigned int cpu)
> {
> - struct tmigr_cpu *tmc = this_cpu_ptr(&tmigr_cpu);
> -
> - WARN_ON_ONCE(!tmc->online || tmc->idle);
> + struct tmigr_cpu *tmc = per_cpu_ptr(&tmigr_cpu, cpu);
> + int ret = 0;
>
> - return 0;
> -}
> + /*
> + * The target CPU must never do the prepare work. Otherwise it may
> + * spuriously activate the old top level group inside the new one
> + * (nevertheless whether old top level group is active or not) and/or
> + * release an uninitialized childmask.
> + */
> + WARN_ON_ONCE(cpu == raw_smp_processor_id());
Silly me! Who else than the boot CPU can do the prepare work for the
boot CPU?
This should be something like:
diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index fae04950487f..8d57f7686bb0 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1673,6 +1673,15 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
lvllist = &tmigr_level_list[top];
if (group->num_children == 1 && 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
+ * it may spuriously activate the old top level group inside
+ * the new one (nevertheless whether old top level group is
+ * active or not) and/or release an uninitialized childmask.
+ */
+ WARN_ON_ONCE(cpu == raw_smp_processor_id());
+
lvllist = &tmigr_level_list[top - 1];
list_for_each_entry(child, lvllist, list) {
if (child->parent)
@@ -1705,14 +1714,6 @@ static int tmigr_cpu_prepare(unsigned int cpu)
struct tmigr_cpu *tmc = per_cpu_ptr(&tmigr_cpu, cpu);
int ret = 0;
- /*
- * The target CPU must never do the prepare work. Otherwise it may
- * spuriously activate the old top level group inside the new one
- * (nevertheless whether old top level group is active or not) and/or
- * release an uninitialized childmask.
- */
- WARN_ON_ONCE(cpu == raw_smp_processor_id());
-
/* Not first online attempt? */
if (tmc->tmgroup)
return ret;
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