5 files changed, 45 insertions, 29 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index f7ed9ee46eb9..cbd0f1b324b9 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -143,6 +143,7 @@ static const char * const task_state_array[] = {
         "x (dead)",             /*  64 */
         "K (wakekill)",         /* 128 */
         "W (waking)",           /* 256 */
+        "P (parked)",           /* 512 */
 };
 
 static inline const char *get_task_state(struct task_struct *tsk)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d35d2b6ddbfb..e692a022527b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -163,9 +163,10 @@ print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 #define TASK_DEAD               64
 #define TASK_WAKEKILL           128
 #define TASK_WAKING             256
-#define TASK_STATE_MAX          512
+#define TASK_PARKED             512
+#define TASK_STATE_MAX          1024
 
-#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKW"
+#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKWP"
 
 extern char ___assert_task_state[1 - 2*!!(
                 sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1)];
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 5a8671e8a67f..e5586caff67a 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -147,7 +147,7 @@ TRACE_EVENT(sched_switch,
                   __print_flags(__entry->prev_state & (TASK_STATE_MAX-1), "|",
                                 { 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },
                                 { 16, "Z" }, { 32, "X" }, { 64, "x" },
-                                { 128, "W" }) : "R",
+                                { 128, "K" }, { 256, "W" }, { 512, "P" }) : "R",
                 __entry->prev_state & TASK_STATE_MAX ? "+" : "",
                 __entry->next_comm, __entry->next_pid, __entry->next_prio)
 );
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 691dc2ef9baf..9eb7fed0bbaa 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -124,12 +124,12 @@ void *kthread_data(struct task_struct *task)
 
 static void __kthread_parkme(struct kthread *self)
 {
-        __set_current_state(TASK_INTERRUPTIBLE);
+        __set_current_state(TASK_PARKED);
         while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
                 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
                         complete(&self->parked);
                 schedule();
-                __set_current_state(TASK_INTERRUPTIBLE);
+                __set_current_state(TASK_PARKED);
         }
         clear_bit(KTHREAD_IS_PARKED, &self->flags);
         __set_current_state(TASK_RUNNING);
@@ -256,8 +256,13 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 }
 EXPORT_SYMBOL(kthread_create_on_node);
 
-static void __kthread_bind(struct task_struct *p, unsigned int cpu)
+static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
 {
+        /* Must have done schedule() in kthread() before we set_task_cpu */
+        if (!wait_task_inactive(p, state)) {
+                WARN_ON(1);
+                return;
+        }
         /* It's safe because the task is inactive. */
         do_set_cpus_allowed(p, cpumask_of(cpu));
         p->flags |= PF_THREAD_BOUND;
@@ -274,12 +279,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu)
  */
 void kthread_bind(struct task_struct *p, unsigned int cpu)
 {
-        /* Must have done schedule() in kthread() before we set_task_cpu */
-        if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
-                WARN_ON(1);
-                return;
-        }
-        __kthread_bind(p, cpu);
+        __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL(kthread_bind);
 
@@ -324,6 +324,22 @@ static struct kthread *task_get_live_kthread(struct task_struct *k)
         return NULL;
 }
 
+static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
+{
+        clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
+        /*
+         * We clear the IS_PARKED bit here as we don't wait
+         * until the task has left the park code. So if we'd
+         * park before that happens we'd see the IS_PARKED bit
+         * which might be about to be cleared.
+         */
+        if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
+                if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
+                        __kthread_bind(k, kthread->cpu, TASK_PARKED);
+                wake_up_state(k, TASK_PARKED);
+        }
+}
+
 /**
  * kthread_unpark - unpark a thread created by kthread_create().
  * @k:          thread created by kthread_create().
@@ -336,20 +352,8 @@ void kthread_unpark(struct task_struct *k)
 {
         struct kthread *kthread = task_get_live_kthread(k);
 
-        if (kthread) {
-                clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
-                /*
-                 * We clear the IS_PARKED bit here as we don't wait
-                 * until the task has left the park code. So if we'd
-                 * park before that happens we'd see the IS_PARKED bit
-                 * which might be about to be cleared.
-                 */
-                if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
-                        if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
-                                __kthread_bind(k, kthread->cpu);
-                        wake_up_process(k);
-                }
-        }
+        if (kthread)
+                __kthread_unpark(k, kthread);
         put_task_struct(k);
 }
 
@@ -407,7 +411,7 @@ int kthread_stop(struct task_struct *k)
         trace_sched_kthread_stop(k);
         if (kthread) {
                 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
-                clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
+                __kthread_unpark(k, kthread);
                 wake_up_process(k);
                 wait_for_completion(&kthread->exited);
         }
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index 8eaed9aa9cf0..02fc5c933673 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -185,8 +185,18 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
         }
         get_task_struct(tsk);
         *per_cpu_ptr(ht->store, cpu) = tsk;
-        if (ht->create)
-                ht->create(cpu);
+        if (ht->create) {
+                /*
+                 * Make sure that the task has actually scheduled out
+                 * into park position, before calling the create
+                 * callback. At least the migration thread callback
+                 * requires that the task is off the runqueue.
+                 */
+                if (!wait_task_inactive(tsk, TASK_PARKED))
+                        WARN_ON(1);
+                else
+                        ht->create(cpu);
+        }
         return 0;
 }