diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2020-09-16 09:27:18 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-11-10 18:38:58 +0100 |
| commit | 1cf12e08bc4d50a76b80c42a3109c53d8794a0c9 (patch) | |
| tree | 0ae7a4475ff2006ed83ba135dceb4faab0d85b2d /kernel/cpu.c | |
| parent | 06249738a41a70f2201a148866899f84cbebc45e (diff) | |
sched/hotplug: Consolidate task migration on CPU unplug
With the new mechanism which kicks tasks off the outgoing CPU at the end of
schedule() the situation on an outgoing CPU right before the stopper thread
brings it down completely is:
- All user tasks and all unbound kernel threads have either been migrated
away or are not running and the next wakeup will move them to a online CPU.
- All per CPU kernel threads, except cpu hotplug thread and the stopper
thread have either been unbound or parked by the responsible CPU hotplug
callback.
That means that at the last step before the stopper thread is invoked the
cpu hotplug thread is the last legitimate running task on the outgoing
CPU.
Add a final wait step right before the stopper thread is kicked which
ensures that any still running tasks on the way to park or on the way to
kick themself of the CPU are either sleeping or gone.
This allows to remove the migrate_tasks() crutch in sched_cpu_dying(). If
sched_cpu_dying() detects that there is still another running task aside of
the stopper thread then it will explode with the appropriate fireworks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201023102346.547163969@infradead.org
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 6ff2578ecf17..fa535eaa4826 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1602,7 +1602,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { .name = "ap:online", }, /* - * Handled on controll processor until the plugged processor manages + * Handled on control processor until the plugged processor manages * this itself. */ [CPUHP_TEARDOWN_CPU] = { @@ -1611,6 +1611,13 @@ static struct cpuhp_step cpuhp_hp_states[] = { .teardown.single = takedown_cpu, .cant_stop = true, }, + + [CPUHP_AP_SCHED_WAIT_EMPTY] = { + .name = "sched:waitempty", + .startup.single = NULL, + .teardown.single = sched_cpu_wait_empty, + }, + /* Handle smpboot threads park/unpark */ [CPUHP_AP_SMPBOOT_THREADS] = { .name = "smpboot/threads:online", |