[PATCH 2/2] Revert "kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function"

[Oleg Nesterov]

This reverts commit 23196f2e5f5d810578a772785807dcdc2b9fdce9.

After the previous change struct kthread can't go away, no need to pin
the stack.

TODO: kill to_live_kthread().

Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
 kernel/kthread.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9d64b65..7891a94 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -88,7 +88,7 @@ void free_kthread_struct(struct task_struct *k)
 static struct kthread *to_live_kthread(struct task_struct *k)
 {
        struct completion *vfork = ACCESS_ONCE(k->vfork_done);
-       if (likely(vfork) && try_get_task_stack(k))
+       if (likely(vfork))
                return __to_kthread(vfork);
        return NULL;
 }
@@ -473,10 +473,8 @@ void kthread_unpark(struct task_struct *k)
 {
        struct kthread *kthread = to_live_kthread(k);
 
-       if (kthread) {
+       if (kthread)
                __kthread_unpark(k, kthread);
-               put_task_stack(k);
-       }
 }
 EXPORT_SYMBOL_GPL(kthread_unpark);
 
@@ -505,7 +503,6 @@ int kthread_park(struct task_struct *k)
                                wait_for_completion(&kthread->parked);
                        }
                }
-               put_task_stack(k);
                ret = 0;
        }
        return ret;
@@ -541,7 +538,6 @@ int kthread_stop(struct task_struct *k)
                __kthread_unpark(k, kthread);
                wake_up_process(k);
                wait_for_completion(&kthread->exited);
-               put_task_stack(k);
        }
        ret = k->exit_code;
        put_task_struct(k);
-- 
2.5.0