1 files changed, 56 insertions, 38 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 12484e5d5..a3bbaee77 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -73,21 +73,24 @@ static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
 	}
 }
 
+static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
+					struct cpu_stop_work *work)
+{
+	list_add_tail(&work->list, &stopper->works);
+	wake_up_process(stopper->thread);
+}
+
 /* queue @work to @stopper.  if offline, @work is completed immediately */
 static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
 {
 	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, 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);
-	} else
+	if (stopper->enabled)
+		__cpu_stop_queue_work(stopper, work);
+	else
 		cpu_stop_signal_done(work->done, false);
-
 	spin_unlock_irqrestore(&stopper->lock, flags);
 }
 
@@ -213,6 +216,31 @@ static int multi_cpu_stop(void *data)
 	return err;
 }
 
+static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
+				    int cpu2, struct cpu_stop_work *work2)
+{
+	struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1);
+	struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);
+	int err;
+
+	lg_double_lock(&stop_cpus_lock, cpu1, cpu2);
+	spin_lock_irq(&stopper1->lock);
+	spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
+
+	err = -ENOENT;
+	if (!stopper1->enabled || !stopper2->enabled)
+		goto unlock;
+
+	err = 0;
+	__cpu_stop_queue_work(stopper1, work1);
+	__cpu_stop_queue_work(stopper2, work2);
+unlock:
+	spin_unlock(&stopper2->lock);
+	spin_unlock_irq(&stopper1->lock);
+	lg_double_unlock(&stop_cpus_lock, cpu1, cpu2);
+
+	return err;
+}
 /**
  * stop_two_cpus - stops two cpus
  * @cpu1: the cpu to stop
@@ -247,24 +275,13 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
 	cpu_stop_init_done(&done, 2);
 	set_state(&msdata, MULTI_STOP_PREPARE);
 
-	/*
-	 * If we observe both CPUs active we know _cpu_down() cannot yet have
-	 * queued its stop_machine works and therefore ours will get executed
-	 * first. Or its not either one of our CPUs that's getting unplugged,
-	 * in which case we don't care.
-	 *
-	 * This relies on the stopper workqueues to be FIFO.
-	 */
-	if (!cpu_active(cpu1) || !cpu_active(cpu2)) {
+	if (cpu1 > cpu2)
+		swap(cpu1, cpu2);
+	if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) {
 		preempt_enable();
 		return -ENOENT;
 	}
 
-	lg_double_lock(&stop_cpus_lock, cpu1, cpu2);
-	cpu_stop_queue_work(cpu1, &work1);
-	cpu_stop_queue_work(cpu2, &work2);
-	lg_double_unlock(&stop_cpus_lock, cpu1, cpu2);
-
 	preempt_enable();
 
 	wait_for_completion(&done.completion);
@@ -452,6 +469,18 @@ repeat:
 	}
 }
 
+void stop_machine_park(int cpu)
+{
+	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+	/*
+	 * Lockless. cpu_stopper_thread() will take stopper->lock and flush
+	 * the pending works before it parks, until then it is fine to queue
+	 * the new works.
+	 */
+	stopper->enabled = false;
+	kthread_park(stopper->thread);
+}
+
 extern void sched_set_stop_task(int cpu, struct task_struct *stop);
 
 static void cpu_stop_create(unsigned int cpu)
@@ -462,26 +491,16 @@ static void cpu_stop_create(unsigned int cpu)
 static void cpu_stop_park(unsigned int cpu)
 {
 	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
-	struct cpu_stop_work *work, *tmp;
-	unsigned long flags;
 
-	/* drain remaining works */
-	spin_lock_irqsave(&stopper->lock, flags);
-	list_for_each_entry_safe(work, tmp, &stopper->works, list) {
-		list_del_init(&work->list);
-		cpu_stop_signal_done(work->done, false);
-	}
-	stopper->enabled = false;
-	spin_unlock_irqrestore(&stopper->lock, flags);
+	WARN_ON(!list_empty(&stopper->works));
 }
 
-static void cpu_stop_unpark(unsigned int cpu)
+void stop_machine_unpark(int cpu)
 {
 	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
 
-	spin_lock_irq(&stopper->lock);
 	stopper->enabled = true;
-	spin_unlock_irq(&stopper->lock);
+	kthread_unpark(stopper->thread);
 }
 
 static struct smp_hotplug_thread cpu_stop_threads = {
@@ -490,9 +509,7 @@ static struct smp_hotplug_thread cpu_stop_threads = {
 	.thread_fn		= cpu_stopper_thread,
 	.thread_comm		= "migration/%u",
 	.create			= cpu_stop_create,
-	.setup			= cpu_stop_unpark,
 	.park			= cpu_stop_park,
-	.pre_unpark		= cpu_stop_unpark,
 	.selfparking		= true,
 };
 
@@ -508,12 +525,13 @@ 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;
 }
 early_initcall(cpu_stop_init);
 
-#ifdef CONFIG_STOP_MACHINE
+#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
 
 static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
 {
@@ -613,4 +631,4 @@ int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 	return ret ?: done.ret;
 }
 
-#endif	/* CONFIG_STOP_MACHINE */
+#endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */