Re: [PATCH 6/7] psi: pressure stall information for CPU, memory, and IO

[Johannes Weiner]

On Wed, May 09, 2018 at 04:33:24PM +0530, Vinayak Menon wrote:
> On 5/8/2018 2:31 AM, Johannes Weiner wrote:
> > +	/* Kick the stats aggregation worker if it's gone to sleep */
> > +	if (!delayed_work_pending(&group->clock_work))
> 
> This causes a crash when the work is scheduled before system_wq is up. In my case when the first
> schedule was called from kthreadd. And I had to do this to make it work.
> if (keventd_up() && !delayed_work_pending(&group->clock_work))
>
> > +		schedule_delayed_work(&group->clock_work, MY_LOAD_FREQ);

I was trying to figure out how this is possible, and it didn't make
sense because we do initialize the system_wq way before kthreadd.

Did you by any chance backport this to a pre-4.10 kernel which does
not have 3347fa092821 ("workqueue: make workqueue available early
during boot") yet?

> > +void psi_task_change(struct task_struct *task, u64 now, int clear, int set)
> > +{
> > +	struct cgroup *cgroup, *parent;
> 
> unused variables

They're used in the next patch, I'll fix that up.

Thanks