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>

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3046a50..c91e30d 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -254,6 +254,8 @@ static int __ref take_cpu_down(void *_param)
                return err;
 
        cpu_notify(CPU_DYING | param->mod, param->hcpu);
+       /* Park the stopper thread */
+       kthread_park(current);
        return 0;
 }
 

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index aaac68c..95d178c 100644 (file)
--- 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);