1 files changed, 28 insertions, 41 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index bc5d1f0b25a4..9b1a7de26979 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -35,17 +35,13 @@ struct kthread_create_info
         struct list_head list;
 };
 
-struct kthread_stop_info
-{
-        struct task_struct *k;
-        int err;
-        struct completion done;
+struct kthread {
+        int should_stop;
+        struct completion exited;
 };
 
-/* Thread stopping is done by setthing this var: lock serializes
- * multiple kthread_stop calls. */
-static DEFINE_MUTEX(kthread_stop_lock);
-static struct kthread_stop_info kthread_stop_info;
+#define to_kthread(tsk) \
+        container_of((tsk)->vfork_done, struct kthread, exited)
 
 /**
  * kthread_should_stop - should this kthread return now?
@@ -56,20 +52,22 @@ static struct kthread_stop_info kthread_stop_info;
  */
 int kthread_should_stop(void)
 {
-        return (kthread_stop_info.k == current);
+        return to_kthread(current)->should_stop;
 }
 EXPORT_SYMBOL(kthread_should_stop);
 
 static int kthread(void *_create)
 {
+        /* Copy data: it's on kthread's stack */
         struct kthread_create_info *create = _create;
-        int (*threadfn)(void *data);
-        void *data;
-        int ret = -EINTR;
+        int (*threadfn)(void *data) = create->threadfn;
+        void *data = create->data;
+        struct kthread self;
+        int ret;
 
-        /* Copy data: it's on kthread's stack */
-        threadfn = create->threadfn;
-        data = create->data;
+        self.should_stop = 0;
+        init_completion(&self.exited);
+        current->vfork_done = &self.exited;
 
         /* OK, tell user we're spawned, wait for stop or wakeup */
         __set_current_state(TASK_UNINTERRUPTIBLE);
@@ -77,15 +75,12 @@ static int kthread(void *_create)
         complete(&create->done);
         schedule();
 
-        if (!kthread_should_stop())
+        ret = -EINTR;
+        if (!self.should_stop)
                 ret = threadfn(data);
 
-        /* It might have exited on its own, w/o kthread_stop.  Check. */
-        if (kthread_should_stop()) {
-                kthread_stop_info.err = ret;
-                complete(&kthread_stop_info.done);
-        }
-        return 0;
+        /* we can't just return, we must preserve "self" on stack */
+        do_exit(ret);
 }
 
 static void create_kthread(struct kthread_create_info *create)
@@ -195,30 +190,22 @@ EXPORT_SYMBOL(kthread_bind);
  */
 int kthread_stop(struct task_struct *k)
 {
+        struct kthread *kthread;
         int ret;
 
-        mutex_lock(&kthread_stop_lock);
-
-        /* It could exit after stop_info.k set, but before wake_up_process. */
-        get_task_struct(k);
-
         trace_sched_kthread_stop(k);
+        get_task_struct(k);
 
-        /* Must init completion *before* thread sees kthread_stop_info.k */
-        init_completion(&kthread_stop_info.done);
-        smp_wmb();
+        kthread = to_kthread(k);
+        barrier(); /* it might have exited */
+        if (k->vfork_done != NULL) {
+                kthread->should_stop = 1;
+                wake_up_process(k);
+                wait_for_completion(&kthread->exited);
+        }
+        ret = k->exit_code;
 
-        /* Now set kthread_should_stop() to true, and wake it up. */
-        kthread_stop_info.k = k;
-        wake_up_process(k);
         put_task_struct(k);
-
-        /* Once it dies, reset stop ptr, gather result and we're done. */
-        wait_for_completion(&kthread_stop_info.done);
-        kthread_stop_info.k = NULL;
-        ret = kthread_stop_info.err;
-        mutex_unlock(&kthread_stop_lock);
-
         trace_sched_kthread_stop_ret(ret);
 
         return ret;