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authorFrederic Weisbecker <frederic@kernel.org>2024-02-25 23:55:07 +0100
committerThomas Gleixner <tglx@linutronix.de>2024-02-26 11:37:32 +0100
commit500f8f9bced86f0c0f2482773bd64a1b7ec9c4e1 (patch)
tree16c613caa4c0ebacf748c44fee3dcd611b739118 /kernel
parenttick: Shut down low-res tick from dying CPU (diff)
downloadlinux-500f8f9bced86f0c0f2482773bd64a1b7ec9c4e1.tar.xz
linux-500f8f9bced86f0c0f2482773bd64a1b7ec9c4e1.zip
tick: Assume timekeeping is correctly handed over upon last offline idle call
The timekeeping duty is handed over from the outgoing CPU on stop machine, then the oneshot tick is stopped right after. Therefore it's guaranteed that the current CPU isn't the timekeeper upon its last call to idle. Besides, calling tick_nohz_idle_stop_tick() while the dying CPU goes into idle suggests that the tick is going to be stopped while it is actually stopped already from the appropriate CPU hotplug state. Remove the confusing call and the obsolete case handling and convert it to a sanity check that verifies the above assumption. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240225225508.11587-16-frederic@kernel.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpu.c1
-rw-r--r--kernel/sched/idle.c1
-rw-r--r--kernel/time/tick-common.c4
-rw-r--r--kernel/time/tick-sched.c13
4 files changed, 6 insertions, 13 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 5a8ad4f5ccf3..7e84a7b0675e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1399,6 +1399,7 @@ void cpuhp_report_idle_dead(void)
struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
BUG_ON(st->state != CPUHP_AP_OFFLINE);
+ tick_assert_timekeeping_handover();
rcutree_report_cpu_dead();
st->state = CPUHP_AP_IDLE_DEAD;
/*
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 31231925f1ec..b15d40cad7ea 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -291,7 +291,6 @@ static void do_idle(void)
local_irq_disable();
if (cpu_is_offline(cpu)) {
- tick_nohz_idle_stop_tick();
cpuhp_report_idle_dead();
arch_cpu_idle_dead();
}
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 9cd09eea06d6..fb0fdec8719a 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -396,6 +396,10 @@ int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
#ifdef CONFIG_HOTPLUG_CPU
+void tick_assert_timekeeping_handover(void)
+{
+ WARN_ON_ONCE(tick_do_timer_cpu == smp_processor_id());
+}
/*
* Stop the tick and transfer the timekeeping job away from a dying cpu.
*/
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 89d16b8ea2c4..269e21590df5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1160,18 +1160,7 @@ static bool report_idle_softirq(void)
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
{
- /*
- * If this CPU is offline and it is the one which updates
- * jiffies, then give up the assignment and let it be taken by
- * the CPU which runs the tick timer next. If we don't drop
- * this here, the jiffies might be stale and do_timer() never
- * gets invoked.
- */
- if (unlikely(!cpu_online(cpu))) {
- if (cpu == tick_do_timer_cpu)
- tick_do_timer_cpu = TICK_DO_TIMER_NONE;
- return false;
- }
+ WARN_ON_ONCE(cpu_is_offline(cpu));
if (unlikely(!tick_sched_flag_test(ts, TS_FLAG_NOHZ)))
return false;