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Commit c00166d8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

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



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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent d8bc8535

include/linux/smpboot.h

+0 −4
Original line number Diff line number Diff line
@@ -24,9 +24,6 @@ struct smpboot_thread_data; 
 *			parked (cpu offline)

 * @unpark:		Optional unpark function, called when the thread is

 *			unparked (cpu online)

 * @pre_unpark:		Optional unpark function, called before the thread is

 *			unparked (cpu online). This is not guaranteed to be

 *			called on the target cpu of the thread. Careful!

 * @cpumask:		Internal state.  To update which threads are unparked,

 *			call smpboot_update_cpumask_percpu_thread().

 * @selfparking:	Thread is not parked by the park function.
@@ -42,7 +39,6 @@ struct smp_hotplug_thread { 
	void				(*cleanup)(unsigned int cpu, bool online);

	void				(*park)(unsigned int cpu);

	void				(*unpark)(unsigned int cpu);

	void				(*pre_unpark)(unsigned int cpu);

	cpumask_var_t			cpumask;

	bool				selfparking;

	const char			*thread_comm;

include/linux/stop_machine.h

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, 
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);

int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);

void stop_machine_park(int cpu);

void stop_machine_unpark(int cpu);



#else	/* CONFIG_SMP */

kernel/cpu.c

+1 −0
Original line number Diff line number Diff line
@@ -475,6 +475,7 @@ static int smpboot_thread_call(struct notifier_block *nfb, 


	case CPU_DOWN_FAILED:

	case CPU_ONLINE:

		stop_machine_unpark(cpu);

		smpboot_unpark_threads(cpu);

		break;

kernel/smpboot.c

+2 −3
Original line number Diff line number Diff line
@@ -222,8 +222,7 @@ static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cp 
{

	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);



	if (ht->pre_unpark)

		ht->pre_unpark(cpu);

	if (!ht->selfparking)

		kthread_unpark(tsk);

}

kernel/stop_machine.c

+9 −1
Original line number Diff line number Diff line
@@ -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;

}