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-rw-r--r--kernel/time/tick-sched.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3319e16f31e5..7c7ec4515983 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -290,16 +290,17 @@ static int __init tick_nohz_full_setup(char *str)
__setup("nohz_full=", tick_nohz_full_setup);
static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
+ unsigned long action,
+ void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
/*
- * If we handle the timekeeping duty for full dynticks CPUs,
- * we can't safely shutdown that CPU.
+ * The boot CPU handles housekeeping duty (unbound timers,
+ * workqueues, timekeeping, ...) on behalf of full dynticks
+ * CPUs. It must remain online when nohz full is enabled.
*/
if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
return NOTIFY_BAD;
@@ -370,6 +371,12 @@ void __init tick_nohz_init(void)
cpu_notifier(tick_nohz_cpu_down_callback, 0);
pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
cpumask_pr_args(tick_nohz_full_mask));
+
+ /*
+ * We need at least one CPU to handle housekeeping work such
+ * as timekeeping, unbound timers, workqueues, ...
+ */
+ WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
}
#endif