Re: lockdep splat during suspend

From: Thomas Gleixner
Date: Thu Nov 17 2016 - 12:23:56 EST


On Thu, 17 Nov 2016, Sebastian Andrzej Siewior wrote:

> On 2016-11-17 13:43:58 [+0100], Borislav Petkov wrote:
> > Hi dudes,
> Hi Boris,
>
> > this is what I'm seeing on 4.9-rc5+tip/master during suspend. (And yes,
> > that printk thing is nuts):
>
> assuming this happens always, could you please try to revert
> 90b14889d2f9 ("kernel/printk: Convert to hotplug state machine")
> and see if it still there? I am curious if this is new or old splat.

It's a new one and that patch simply missed the fact, that the actions in
the original notifier were all w/o FROZEN, but the conversion dropped
that. Which probably explains the splat because suspend/resume is where the
FROZEN stuff happens.

Boris, does the patch below fix the issue for you ?

Thanks,

tglx

8<-----------------------

--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2194,8 +2194,10 @@ void resume_console(void)
*/
static int console_cpu_notify(unsigned int cpu)
{
- console_lock();
- console_unlock();
+ if (!cpuhp_tasks_frozen) {
+ console_lock();
+ console_unlock();
+ }
return 0;
}