linux-kernel - [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill kthreadd_task_init

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Date:	Tue, 1 Sep 2009 18:52:35 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	arjan@...radead.org, jeremy@...p.org, mschmidt@...hat.com,
	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tj@...nel.org, tglx@...utronix.de,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-tip-commits@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill
	kthreadd_task_init_done

On 09/01, Oleg Nesterov wrote:
>
> On 09/01, Ingo Molnar wrote:
> >
> > * Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > > On 09/01, Ingo Molnar wrote:
> > > >
> > > > * Oleg Nesterov <oleg@...hat.com> wrote:
> > > >
> > > > > Yes, this should work. But I _think_ we can make the better fix...
> > > > >
> > > > > I'll try to make the patch soon. Afaics we don't need
> > > > > kthreadd_task_init_done.
> > > >
> > > > ok.
> > >
> > > Just in case, the patch is ready. [...]
> >
> > yes - that's roughly the cleanup i referred to in the commit log.
> >
> > way too late for -rc8 though - the minimal fix i did _might_ be
> > eligible.
> >
> > agreed?
>
> Agreed. Then I will sent the patch on top of this change.

OK, I am sending the patch on top of your fix. Not sure how to really
test it, but at least the kernel works when I apply the debugging patch
below on top.

Oleg.

--- WAIT/init/main.c~DBG	2009-09-01 15:49:36.000000000 +0200
+++ WAIT/init/main.c	2009-09-01 17:53:28.000000000 +0200
@@ -455,7 +455,6 @@ static noinline void __init_refok rest_i
 {
 	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
 	numa_default_policy();
-	kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
 	unlock_kernel();
 
 	/*
@@ -466,6 +465,12 @@ static noinline void __init_refok rest_i
 	rcu_scheduler_starting();
 	preempt_enable_no_resched();
 	schedule();
+
+	printk(KERN_INFO "XXX rest_init - sleeeeep\n");
+//	schedule_timeout_interruptible(HZ);
+	kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
+	printk(KERN_INFO "XXX rest_init - kthreadd started\n");
+
 	preempt_disable();
 
 	/* Call into cpu_idle with preempt disabled */
@@ -877,10 +882,18 @@ static noinline int init_post(void)
 	panic("No init found.  Try passing init= option to kernel.");
 }
 
+int ktfunc(void *arg)
+{
+	printk(KERN_INFO "XXX ktfunc - alive!\n");
+	return 0;
+}
+
 static int __init kernel_init(void * unused)
 {
 	lock_kernel();
 
+	printk(KERN_INFO "XXX kernel_init - call kthread_run, kthreadd=%p\n", kthreadd_task);
+	kthread_run(ktfunc, NULL, "xxx");
 	/*
 	 * init can allocate pages on any node
 	 */

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