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stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark()

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1. Change smpboot_unpark_thread() to check ->selfparking, just
   like smpboot_park_thread() does.

2. Introduce stop_machine_unpark() which sets ->enabled and calls
   kthread_unpark().

3. Change smpboot_thread_call() and cpu_stop_init() to call
   stop_machine_unpark() by hand.

This way:

    - IMO the ->selfparking logic becomes more consistent.

    - We can kill the smp_hotplug_thread->pre_unpark() method.

    - We can easily unpark the stopper thread earlier. Say, we
      can move stop_machine_unpark() from smpboot_thread_call()
      to sched_cpu_active() as Peter suggests.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151009160049.GA10166@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov
2015-10-09 18:00:49 +02:00
committed by Ingo Molnar
parent d8bc853582
commit c00166d87e
5 changed files with 13 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
kernel/stop_machine.c
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@@ -513,6 +513,14 @@ static void cpu_stop_unpark(unsigned int cpu)
spin_unlock_irq(&stopper->lock);
}
void stop_machine_unpark(int cpu)
{
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
cpu_stop_unpark(cpu);
kthread_unpark(stopper->thread);
}
static struct smp_hotplug_thread cpu_stop_threads = {
.store = &cpu_stopper.thread,
.thread_should_run = cpu_stop_should_run,
@@ -521,7 +529,6 @@ static struct smp_hotplug_thread cpu_stop_threads = {
.create = cpu_stop_create,
.setup = cpu_stop_unpark,
.park = cpu_stop_park,
.pre_unpark = cpu_stop_unpark,
.selfparking = true,
};
@@ -537,6 +544,7 @@ static int __init cpu_stop_init(void)
}
BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
stop_machine_unpark(raw_smp_processor_id());
stop_machine_initialized = true;
return 0;
}