From b5c5442bb6bce0c67701d55124be561043a51faf Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 29 Apr 2013 15:05:12 -0700 Subject: kthread: kill task_get_live_kthread() task_get_live_kthread() looks confusing and unneeded. It does get_task_struct() but only kthread_stop() needs this, it can be called even if the calller doesn't have a reference when we know that this kthread can't exit until we do kthread_stop(). kthread_park() and kthread_unpark() do not need get_task_struct(), the callers already have the reference. And it can not help if we can race with the exiting kthread anyway, kthread_park() can hang forever in this case. Change kthread_park() and kthread_unpark() to use to_live_kthread(), change kthread_stop() to do get_task_struct() by hand and remove task_get_live_kthread(). Signed-off-by: Oleg Nesterov Cc: Thomas Gleixner Cc: Namhyung Kim Cc: "Paul E. McKenney" Cc: Peter Zijlstra Cc: Rusty Russell Cc: "Srivatsa S. Bhat" Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kthread.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) (limited to 'kernel/kthread.c') diff --git a/kernel/kthread.c b/kernel/kthread.c index a84dee265f94..9b12d65186f7 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -324,12 +324,6 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), return p; } -static struct kthread *task_get_live_kthread(struct task_struct *k) -{ - get_task_struct(k); - return to_live_kthread(k); -} - static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) { clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); @@ -356,11 +350,10 @@ static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) */ void kthread_unpark(struct task_struct *k) { - struct kthread *kthread = task_get_live_kthread(k); + struct kthread *kthread = to_live_kthread(k); if (kthread) __kthread_unpark(k, kthread); - put_task_struct(k); } /** @@ -377,7 +370,7 @@ void kthread_unpark(struct task_struct *k) */ int kthread_park(struct task_struct *k) { - struct kthread *kthread = task_get_live_kthread(k); + struct kthread *kthread = to_live_kthread(k); int ret = -ENOSYS; if (kthread) { @@ -390,7 +383,6 @@ int kthread_park(struct task_struct *k) } ret = 0; } - put_task_struct(k); return ret; } @@ -411,10 +403,13 @@ int kthread_park(struct task_struct *k) */ int kthread_stop(struct task_struct *k) { - struct kthread *kthread = task_get_live_kthread(k); + struct kthread *kthread; int ret; trace_sched_kthread_stop(k); + + get_task_struct(k); + kthread = to_live_kthread(k); if (kthread) { set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); __kthread_unpark(k, kthread); @@ -422,10 +417,9 @@ int kthread_stop(struct task_struct *k) wait_for_completion(&kthread->exited); } ret = k->exit_code; - put_task_struct(k); - trace_sched_kthread_stop_ret(ret); + trace_sched_kthread_stop_ret(ret); return ret; } EXPORT_SYMBOL(kthread_stop); -- cgit v1.2.3-55-g7522