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Commit 860a0ffa authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

stop_machine: Store task reference in a separate per cpu variable 



To allow the stopper thread being managed by the smpboot thread
infrastructure separate out the task storage from the stopper data
structure.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard Weinberger <rw@linutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130131120741.626690384@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7d7e499f

kernel/stop_machine.c

+16 −16
Original line number Diff line number Diff line
@@ -37,10 +37,10 @@ struct cpu_stopper { 
	spinlock_t		lock;

	bool			enabled;	/* is this stopper enabled? */

	struct list_head	works;		/* list of pending works */

	struct task_struct	*thread;	/* stopper thread */

};



static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);

static DEFINE_PER_CPU(struct task_struct *, cpu_stopper_task);

static bool stop_machine_initialized = false;



static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
@@ -62,16 +62,18 @@ static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed) 
}



/* queue @work to @stopper.  if offline, @work is completed immediately */

static void cpu_stop_queue_work(struct cpu_stopper *stopper,

				struct cpu_stop_work *work)

static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)

{

	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);

	struct task_struct *p = per_cpu(cpu_stopper_task, cpu);



	unsigned long flags;



	spin_lock_irqsave(&stopper->lock, flags);



	if (stopper->enabled) {

		list_add_tail(&work->list, &stopper->works);

		wake_up_process(stopper->thread);

		wake_up_process(p);

	} else

		cpu_stop_signal_done(work->done, false);
@@ -108,7 +110,7 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) 
	struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };



	cpu_stop_init_done(&done, 1);

	cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work);

	cpu_stop_queue_work(cpu, &work);

	wait_for_completion(&done.completion);

	return done.executed ? done.ret : -ENOENT;

}
@@ -130,7 +132,7 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, 
			struct cpu_stop_work *work_buf)

{

	*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };

	cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf);

	cpu_stop_queue_work(cpu, work_buf);

}



/* static data for stop_cpus */
@@ -159,8 +161,7 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask, 
	 */

	preempt_disable();

	for_each_cpu(cpu, cpumask)

		cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu),

				    &per_cpu(stop_cpus_work, cpu));

		cpu_stop_queue_work(cpu, &per_cpu(stop_cpus_work, cpu));

	preempt_enable();

}
@@ -304,12 +305,11 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, 
{

	unsigned int cpu = (unsigned long)hcpu;

	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);

	struct task_struct *p;

	struct task_struct *p = per_cpu(cpu_stopper_task, cpu);



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_UP_PREPARE:

		BUG_ON(stopper->thread || stopper->enabled ||

		       !list_empty(&stopper->works));

		BUG_ON(p || stopper->enabled || !list_empty(&stopper->works));

		p = kthread_create_on_node(cpu_stopper_thread,

					   stopper,

					   cpu_to_node(cpu),
@@ -319,12 +319,12 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, 
		get_task_struct(p);

		kthread_bind(p, cpu);

		sched_set_stop_task(cpu, p);

		stopper->thread = p;

		per_cpu(cpu_stopper_task, cpu) = p;

		break;



	case CPU_ONLINE:

		/* strictly unnecessary, as first user will wake it */

		wake_up_process(stopper->thread);

		wake_up_process(p);

		/* mark enabled */

		spin_lock_irq(&stopper->lock);

		stopper->enabled = true;
@@ -339,7 +339,7 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, 


		sched_set_stop_task(cpu, NULL);

		/* kill the stopper */

		kthread_stop(stopper->thread);

		kthread_stop(p);

		/* drain remaining works */

		spin_lock_irq(&stopper->lock);

		list_for_each_entry(work, &stopper->works, list)
@@ -347,8 +347,8 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, 
		stopper->enabled = false;

		spin_unlock_irq(&stopper->lock);

		/* release the stopper */

		put_task_struct(stopper->thread);

		stopper->thread = NULL;

		put_task_struct(p);

		per_cpu(cpu_stopper_task, cpu) = NULL;

		break;

	}

#endif