cpu/hotplug: Unpark smpboot threads from the state machine

Handle the smpboot threads in the state machine.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.295777684@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

6 files changed, 13 insertions, 45 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 78989f20420f..83f35767016d 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -78,7 +78,7 @@ enum {
         /* migration should happen before other stuff but after perf */
         CPU_PRI_PERF            = 20,
         CPU_PRI_MIGRATION       = 10,
-        CPU_PRI_SMPBOOT         = 9,
+
         /* bring up workqueues before normal notifiers and down after */
         CPU_PRI_WORKQUEUE_UP    = 5,
         CPU_PRI_WORKQUEUE_DOWN  = -5,
@@ -172,7 +172,6 @@ static inline void __unregister_cpu_notifier(struct notifier_block *nb)
 }
 #endif
 
-void smpboot_thread_init(void);
 int cpu_up(unsigned int cpu);
 void notify_cpu_starting(unsigned int cpu);
 extern void cpu_maps_update_begin(void);
@@ -221,10 +220,6 @@ static inline void cpu_notifier_register_done(void)
 {
 }
 
-static inline void smpboot_thread_init(void)
-{
-}
-
 #endif /* CONFIG_SMP */
 extern struct bus_type cpu_subsys;
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 2f2e5d9711c4..38679106fddd 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -11,6 +11,7 @@ enum cpuhp_state {
         CPUHP_AP_ONLINE,
         CPUHP_TEARDOWN_CPU,
         CPUHP_CPU_SET_ACTIVE,
+        CPUHP_SMPBOOT_THREADS,
         CPUHP_NOTIFY_ONLINE,
         CPUHP_ONLINE_DYN,
         CPUHP_ONLINE_DYN_END            = CPUHP_ONLINE_DYN + 30,
diff --git a/init/main.c b/init/main.c
index c2ea72362ee3..55563fd36be3 100644
--- a/init/main.c
+++ b/init/main.c
@@ -388,7 +388,6 @@ static noinline void __init_refok rest_init(void)
         int pid;
 
         rcu_scheduler_starting();
-        smpboot_thread_init();
         /*
          * We need to spawn init first so that it obtains pid 1, however
          * the init task will end up wanting to create kthreads, which, if
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 65e34d34ca93..3ec86bc414b7 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -481,8 +481,6 @@ static int takedown_cpu(unsigned int cpu)
         else
                 synchronize_rcu();
 
-        smpboot_park_threads(cpu);
-
         /*
          * Prevent irq alloc/free while the dying cpu reorganizes the
          * interrupt affinities.
@@ -612,38 +610,6 @@ int cpu_down(unsigned int cpu)
 EXPORT_SYMBOL(cpu_down);
 #endif /*CONFIG_HOTPLUG_CPU*/
 
-/*
- * Unpark per-CPU smpboot kthreads at CPU-online time.
- */
-static int smpboot_thread_call(struct notifier_block *nfb,
-                               unsigned long action, void *hcpu)
-{
-        int cpu = (long)hcpu;
-
-        switch (action & ~CPU_TASKS_FROZEN) {
-
-        case CPU_DOWN_FAILED:
-        case CPU_ONLINE:
-                smpboot_unpark_threads(cpu);
-                break;
-
-        default:
-                break;
-        }
-
-        return NOTIFY_OK;
-}
-
-static struct notifier_block smpboot_thread_notifier = {
-        .notifier_call = smpboot_thread_call,
-        .priority = CPU_PRI_SMPBOOT,
-};
-
-void smpboot_thread_init(void)
-{
-        register_cpu_notifier(&smpboot_thread_notifier);
-}
-
 /**
  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
  * @cpu: cpu that just started
@@ -959,6 +925,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
                 .startup                = cpuhp_set_cpu_active,
                 .teardown               = NULL,
         },
+        [CPUHP_SMPBOOT_THREADS] = {
+                .name                   = "smpboot:threads",
+                .startup                = smpboot_unpark_threads,
+                .teardown               = smpboot_park_threads,
+        },
         [CPUHP_NOTIFY_ONLINE] = {
                 .name                   = "notify:online",
                 .startup                = notify_online,
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index d264f59bff56..13bc43d1fb22 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -226,7 +226,7 @@ static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cp
                 kthread_unpark(tsk);
 }
 
-void smpboot_unpark_threads(unsigned int cpu)
+int smpboot_unpark_threads(unsigned int cpu)
 {
         struct smp_hotplug_thread *cur;
 
@@ -235,6 +235,7 @@ void smpboot_unpark_threads(unsigned int cpu)
                 if (cpumask_test_cpu(cpu, cur->cpumask))
                         smpboot_unpark_thread(cur, cpu);
         mutex_unlock(&smpboot_threads_lock);
+        return 0;
 }
 
 static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
@@ -245,7 +246,7 @@ static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
                 kthread_park(tsk);
 }
 
-void smpboot_park_threads(unsigned int cpu)
+int smpboot_park_threads(unsigned int cpu)
 {
         struct smp_hotplug_thread *cur;
 
@@ -253,6 +254,7 @@ void smpboot_park_threads(unsigned int cpu)
         list_for_each_entry_reverse(cur, &hotplug_threads, list)
                 smpboot_park_thread(cur, cpu);
         mutex_unlock(&smpboot_threads_lock);
+        return 0;
 }
 
 static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
diff --git a/kernel/smpboot.h b/kernel/smpboot.h
index 72415a0eb955..6b5f02017be3 100644
--- a/kernel/smpboot.h
+++ b/kernel/smpboot.h
@@ -14,7 +14,7 @@ static inline void idle_threads_init(void) { }
 #endif
 
 int smpboot_create_threads(unsigned int cpu);
-void smpboot_park_threads(unsigned int cpu);
-void smpboot_unpark_threads(unsigned int cpu);
+int smpboot_park_threads(unsigned int cpu);
+int smpboot_unpark_threads(unsigned int cpu);
 
 #endif