kthreads: simplify the startup synchronization (cdd140bd) · Commits · 戴 / test

We use two completions two create the kernel thread, this is a bit ugly. kthread() wakes up create_kthread() via ->started, then create_kthread() wakes up the caller kthread_create() via ->done. But kthread() does not need to wait for kthread(), it can just return. Instead kthread() itself can wake up the caller of kthread_create(). Kill kthread_create_info->started, ->done is enough. This improves the scalability a bit and sijmplifies the code. The only problem if kernel_thread() fails, in that case create_kthread() must do complete(&create->done). Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Vitaliy Gusev <vgusev@openvz.org Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/kthread.c

+4 −7

Original line number	Diff line number	Diff line
		@@ -27,7 +27,6 @@ struct kthread_create_info
		/* Information passed to kthread() from kthreadd. */
		int (threadfn)(void data);
		void *data;
		struct completion started;

		/* Result passed back to kthread_create() from kthreadd. */
		struct task_struct *result;
		@@ -75,7 +74,7 @@ static int kthread(void *_create)
		/* OK, tell user we're spawned, wait for stop or wakeup */
		__set_current_state(TASK_UNINTERRUPTIBLE);
		create->result = current;
		complete(&create->started);
		complete(&create->done);
		schedule();

		if (!kthread_should_stop())
		@@ -95,12 +94,11 @@ static void create_kthread(struct kthread_create_info *create)

		/* We want our own signal handler (we take no signals by default). */
		pid = kernel_thread(kthread, create, CLONE_FS \| CLONE_FILES \| SIGCHLD);
		if (pid < 0)
		if (pid < 0) {
		create->result = ERR_PTR(pid);
		else
		wait_for_completion(&create->started);
		complete(&create->done);
		}
		}

		/**
		* kthread_create - create a kthread.
		@@ -130,7 +128,6 @@ struct task_struct kthread_create(int (threadfn)(void *data),

		create.threadfn = threadfn;
		create.data = data;
		init_completion(&create.started);
		init_completion(&create.done);

		spin_lock(&kthread_create_lock);

Admin message