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kthreads: simplify the startup synchronization 

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>
This commit is contained in:
Oleg Nesterov 2009-06-17 16:27:43 -07:00 committed by Linus Torvalds
parent e1eb1ebcca
commit cdd140bdd6
1 changed files with 4 additions and 7 deletions
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11
kernel/kthread.c
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@ -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())
@ -95,11 +94,10 @@ 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);
complete(&create->done);
}
}
/**
@ -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);