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 <[email protected]> --- kernel/kthread.c | 20 +++++++------------- 1 files changed, 7 insertions(+), 13 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index fa4a013..d345f4e 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); -} - /** * kthread_unpark - unpark a thread created by kthread_create(). * @k: thread created by kthread_create(). @@ -340,7 +334,7 @@ static struct kthread *task_get_live_kthread(struct task_struct *k) */ void kthread_unpark(struct task_struct *k) { - struct kthread *kthread = task_get_live_kthread(k); + struct kthread *kthread = to_live_kthread(k); if (kthread) { clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); @@ -356,7 +350,6 @@ void kthread_unpark(struct task_struct *k) wake_up_process(k); } } - put_task_struct(k); } /** @@ -373,7 +366,7 @@ 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) { @@ -386,7 +379,6 @@ int kthread_park(struct task_struct *k) } ret = 0; } - put_task_struct(k); return ret; } @@ -407,10 +399,13 @@ 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); clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); @@ -418,10 +413,9 @@ 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); -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
