stop_machine: Use smpboot threads

Use the smpboot thread infrastructure. Mark the stopper thread
selfparking and park it after it has finished the take_cpu_down()
work.

Signed-off-by: Thomas 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/20130131120741.686315164@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 50 insertions, 86 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index aaac68c5c3be..95d178c62d5a 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -18,7 +18,7 @@
 #include <linux/stop_machine.h>
 #include <linux/interrupt.h>
 #include <linux/kallsyms.h>
-
+#include <linux/smpboot.h>
 #include <linux/atomic.h>
 
 /*
@@ -245,20 +245,25 @@ int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
         return ret;
 }
 
-static int cpu_stopper_thread(void *data)
+static int cpu_stop_should_run(unsigned int cpu)
+{
+        struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+        unsigned long flags;
+        int run;
+
+        spin_lock_irqsave(&stopper->lock, flags);
+        run = !list_empty(&stopper->works);
+        spin_unlock_irqrestore(&stopper->lock, flags);
+        return run;
+}
+
+static void cpu_stopper_thread(unsigned int cpu)
 {
-        struct cpu_stopper *stopper = data;
+        struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
         struct cpu_stop_work *work;
         int ret;
 
 repeat:
-        set_current_state(TASK_INTERRUPTIBLE);  /* mb paired w/ kthread_stop */
-
-        if (kthread_should_stop()) {
-                __set_current_state(TASK_RUNNING);
-                return 0;
-        }
-
         work = NULL;
         spin_lock_irq(&stopper->lock);
         if (!list_empty(&stopper->works)) {
@@ -274,8 +279,6 @@ repeat:
                 struct cpu_stop_done *done = work->done;
                 char ksym_buf[KSYM_NAME_LEN] __maybe_unused;
 
-                __set_current_state(TASK_RUNNING);
-
                 /* cpu stop callbacks are not allowed to sleep */
                 preempt_disable();
 
@@ -291,87 +294,55 @@ repeat:
                                           ksym_buf), arg);
 
                 cpu_stop_signal_done(done, true);
-        } else
-                schedule();
-
-        goto repeat;
+                goto repeat;
+        }
 }
 
 extern void sched_set_stop_task(int cpu, struct task_struct *stop);
 
-/* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */
-static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb,
-                                           unsigned long action, void *hcpu)
+static void cpu_stop_create(unsigned int cpu)
+{
+        sched_set_stop_task(cpu, per_cpu(cpu_stopper_task, cpu));
+}
+
+static void cpu_stop_park(unsigned int cpu)
 {
-        unsigned int cpu = (unsigned long)hcpu;
         struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
-        struct task_struct *p = per_cpu(cpu_stopper_task, cpu);
+        struct cpu_stop_work *work;
+        unsigned long flags;
 
-        switch (action & ~CPU_TASKS_FROZEN) {
-        case CPU_UP_PREPARE:
-                BUG_ON(p || stopper->enabled || !list_empty(&stopper->works));
-                p = kthread_create_on_node(cpu_stopper_thread,
-                                           stopper,
-                                           cpu_to_node(cpu),
-                                           "migration/%d", cpu);
-                if (IS_ERR(p))
-                        return notifier_from_errno(PTR_ERR(p));
-                get_task_struct(p);
-                kthread_bind(p, cpu);
-                sched_set_stop_task(cpu, p);
-                per_cpu(cpu_stopper_task, cpu) = p;
-                break;
-
-        case CPU_ONLINE:
-                /* strictly unnecessary, as first user will wake it */
-                wake_up_process(p);
-                /* mark enabled */
-                spin_lock_irq(&stopper->lock);
-                stopper->enabled = true;
-                spin_unlock_irq(&stopper->lock);
-                break;
-
-#ifdef CONFIG_HOTPLUG_CPU
-        case CPU_UP_CANCELED:
-        case CPU_POST_DEAD:
-        {
-                struct cpu_stop_work *work;
-
-                sched_set_stop_task(cpu, NULL);
-                /* kill the stopper */
-                kthread_stop(p);
-                /* drain remaining works */
-                spin_lock_irq(&stopper->lock);
-                list_for_each_entry(work, &stopper->works, list)
-                        cpu_stop_signal_done(work->done, false);
-                stopper->enabled = false;
-                spin_unlock_irq(&stopper->lock);
-                /* release the stopper */
-                put_task_struct(p);
-                per_cpu(cpu_stopper_task, cpu) = NULL;
-                break;
-        }
-#endif
-        }
+        /* drain remaining works */
+        spin_lock_irqsave(&stopper->lock, flags);
+        list_for_each_entry(work, &stopper->works, list)
+                cpu_stop_signal_done(work->done, false);
+        stopper->enabled = false;
+        spin_unlock_irqrestore(&stopper->lock, flags);
+}
 
-        return NOTIFY_OK;
+static void cpu_stop_unpark(unsigned int cpu)
+{
+        struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
+
+        spin_lock_irq(&stopper->lock);
+        stopper->enabled = true;
+        spin_unlock_irq(&stopper->lock);
 }
 
-/*
- * Give it a higher priority so that cpu stopper is available to other
- * cpu notifiers.  It currently shares the same priority as sched
- * migration_notifier.
- */
-static struct notifier_block __cpuinitdata cpu_stop_cpu_notifier = {
-        .notifier_call  = cpu_stop_cpu_callback,
-        .priority       = 10,
+static struct smp_hotplug_thread cpu_stop_threads = {
+        .store                  = &cpu_stopper_task,
+        .thread_should_run      = cpu_stop_should_run,
+        .thread_fn              = cpu_stopper_thread,
+        .thread_comm            = "migration/%u",
+        .create                 = cpu_stop_create,
+        .setup                  = cpu_stop_unpark,
+        .park                   = cpu_stop_park,
+        .unpark                 = cpu_stop_unpark,
+        .selfparking            = true,
 };
 
 static int __init cpu_stop_init(void)
 {
-        void *bcpu = (void *)(long)smp_processor_id();
         unsigned int cpu;
-        int err;
 
         for_each_possible_cpu(cpu) {
                 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
@@ -380,15 +351,8 @@ static int __init cpu_stop_init(void)
                 INIT_LIST_HEAD(&stopper->works);
         }
 
-        /* start one for the boot cpu */
-        err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE,
-                                    bcpu);
-        BUG_ON(err != NOTIFY_OK);
-        cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu);
-        register_cpu_notifier(&cpu_stop_cpu_notifier);
-
+        BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
         stop_machine_initialized = true;
-
         return 0;
 }
 early_initcall(cpu_stop_init);