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Groups > linux.kernel > #1241242
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [RFC][PATCH] sched: Start stopper early |
| Date | 2015-10-07 10:50 +0200 |
| Message-ID | <qgSAa-86i-35@gated-at.bofh.it> (permalink) |
| Organization | linux.* mail to news gateway |
Hi,
So Heiko reported some 'interesting' fail where stop_two_cpus() got
stuck in multi_cpu_stop() with one cpu waiting for another that never
happens.
It _looks_ like the 'other' cpu isn't running and the current best
theory is that we race on cpu-up and get the stop_two_cpus() call in
before the stopper task is running.
This _is_ possible because we set 'online && active' _before_ we do the
smpboot_unpark thing because of ONLINE notifier order.
The below test patch manually starts the stopper task early.
It boots and hotplugs a cpu on my test box so its not insta broken.
---
kernel/sched/core.c | 7 ++++++-
kernel/stop_machine.c | 5 +++++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1764a0f..9a56ef7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5542,14 +5542,19 @@ static void set_cpu_rq_start_time(void)
rq->age_stamp = sched_clock_cpu(cpu);
}
+extern void cpu_stopper_unpark(unsigned int cpu);
+
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
+ int cpu = (long)hcpu;
+
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_STARTING:
set_cpu_rq_start_time();
return NOTIFY_OK;
case CPU_ONLINE:
+ cpu_stopper_unpark(cpu);
/*
* At this point a starting CPU has marked itself as online via
* set_cpu_online(). But it might not yet have marked itself
@@ -5558,7 +5563,7 @@ static int sched_cpu_active(struct notifier_block *nfb,
* Thus, fall-through and help the starting CPU along.
*/
case CPU_DOWN_FAILED:
- set_cpu_active((long)hcpu, true);
+ set_cpu_active(cpu, true);
return NOTIFY_OK;
default:
return NOTIFY_DONE;
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 12484e5..c674371 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -496,6 +496,11 @@ static struct smp_hotplug_thread cpu_stop_threads = {
.selfparking = true,
};
+void cpu_stopper_unpark(unsigned int cpu)
+{
+ kthread_unpark(per_cpu(cpu_stopper.thread, cpu));
+}
+
static int __init cpu_stop_init(void)
{
unsigned int cpu;
--
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[RFC][PATCH] sched: Start stopper early Peter Zijlstra <peterz@infradead.org> - 2015-10-07 10:50 +0200
Re: [RFC][PATCH] sched: Start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-07 14:40 +0200
Re: [RFC][PATCH] sched: Start stopper early Peter Zijlstra <peterz@infradead.org> - 2015-10-07 14:40 +0200
Re: [RFC][PATCH] sched: Start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-07 15:30 +0200
Re: [RFC][PATCH] sched: Start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-07 15:30 +0200
Re: Re: [RFC][PATCH] sched: Start stopper early kbuild test robot <lkp@intel.com> - 2015-10-07 15:40 +0200
[PATCH 0/3] (Was: [RFC][PATCH] sched: Start stopper early) Oleg Nesterov <oleg@redhat.com> - 2015-10-08 17:00 +0200
[PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Oleg Nesterov <oleg@redhat.com> - 2015-10-08 17:00 +0200
Re: [PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Peter Zijlstra <peterz@infradead.org> - 2015-10-14 17:40 +0200
Re: [PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Oleg Nesterov <oleg@redhat.com> - 2015-10-14 21:10 +0200
Re: [PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Peter Zijlstra <peterz@infradead.org> - 2015-10-14 22:40 +0200
Re: [PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Oleg Nesterov <oleg@redhat.com> - 2015-10-15 19:10 +0200
Re: [PATCH 1/3] stop_machine: ensure that a queued callback will be called before cpu_stop_park() Peter Zijlstra <peterz@infradead.org> - 2015-10-16 13:00 +0200
[PATCH 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Oleg Nesterov <oleg@redhat.com> - 2015-10-08 17:00 +0200
Re: [PATCH 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Peter Zijlstra <peterz@infradead.org> - 2015-10-08 17:10 +0200
Re: [PATCH 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Oleg Nesterov <oleg@redhat.com> - 2015-10-08 18:10 +0200
Re: [PATCH 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Oleg Nesterov <oleg@redhat.com> - 2015-10-08 18:20 +0200
[PATCH v2 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Oleg Nesterov <oleg@redhat.com> - 2015-10-08 19:10 +0200
Re: [PATCH v2 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Peter Zijlstra <peterz@infradead.org> - 2015-10-09 18:40 +0200
Re: [PATCH v2 3/3] stop_machine: change cpu_stop_queue_two_works() to rely on stopper->enabled Oleg Nesterov <oleg@redhat.com> - 2015-10-09 18:50 +0200
[PATCH 2/3] stop_machine: introduce __cpu_stop_queue_work() and cpu_stop_queue_two_works() Oleg Nesterov <oleg@redhat.com> - 2015-10-08 17:00 +0200
Re: [RFC][PATCH] sched: Start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-08 20:10 +0200
Re: [RFC][PATCH] sched: Start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-08 21:00 +0200
[PATCH 0/3] make stopper threads more "selfparking" Oleg Nesterov <oleg@redhat.com> - 2015-10-09 18:10 +0200
[PATCH 2/3] stop_machine: kill cpu_stop_threads->setup() and cpu_stop_unpark() Oleg Nesterov <oleg@redhat.com> - 2015-10-09 18:10 +0200
[PATCH 3/3] sched: start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-09 18:10 +0200
Re: [PATCH 3/3] sched: start stopper early Oleg Nesterov <oleg@redhat.com> - 2015-10-09 19:00 +0200
[PATCH 1/3] stop_machine: kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark() Oleg Nesterov <oleg@redhat.com> - 2015-10-09 18:10 +0200
Re: [RFC][PATCH] sched: Start stopper early Heiko Carstens <heiko.carstens@de.ibm.com> - 2015-10-16 10:30 +0200
Re: [RFC][PATCH] sched: Start stopper early Peter Zijlstra <peterz@infradead.org> - 2015-10-16 12:00 +0200
Re: [RFC][PATCH] sched: Start stopper early Heiko Carstens <heiko.carstens@de.ibm.com> - 2015-10-16 14:10 +0200
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