Oops on Power8 (was Re: [PATCH v2 1/7] workqueue: make workqueue available early during boot)

[Tejun Heo]

Hello, Michael.

On Mon, Oct 10, 2016 at 09:22:55PM +1100, Michael Ellerman wrote:
> This patch seems to be causing one of my Power8 boxes not to boot.
> 
> Specifically commit 3347fa092821 ("workqueue: make workqueue available
> early during boot") in linux-next.
> 
> If I revert this on top of next-20161005 then the machine boots again.
> 
> I've attached the oops below. It looks like the cfs_rq of p->se is NULL?

Hah, weird that it's arch dependent, or maybe it's just different
config options.  Most likely, it's caused by workqueue_init() call
being moved too early.  Can you please try the following patch and see
whether the problem goes away?

Thanks.

diff --git a/init/main.c b/init/main.c
index 5c4fd68..fe4fa47 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1013,7 +1013,7 @@ static noinline void __init kernel_init_freeable(void)
 
 	smp_prepare_cpus(setup_max_cpus);
 
-	workqueue_init();
+	//workqueue_init();
 
 	do_pre_smp_initcalls();
 	lockup_detector_init();
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ad0cd43..400f5e2 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5585,3 +5585,4 @@ int __init workqueue_init(void)
 
 	return 0;
 }
+early_initcall(workqueue_init);