Re: [PATCH] remoteproc: Create a separate workqueue for recovery tasks

[rishabhb]

On 2020-12-21 16:35, Bjorn Andersson wrote:
> On Thu 17 Dec 12:49 CST 2020, Alex Elder wrote:
>
> > On 12/17/20 12:21 PM, rishabhb@xxxxxxxxxxxxxx wrote:
> > > On 2020-12-17 08:12, Alex Elder wrote:
> > > > On 12/15/20 4:55 PM, Bjorn Andersson wrote:
> > > > > On Sat 12 Dec 14:48 CST 2020, Rishabh Bhatnagar wrote:
> > > > >
> > > > > > Create an unbound high priority workqueue for recovery tasks.
> > > >
> > > > I have been looking at a different issue that is caused by
> > > > crash notification.
> > > >
> > > > What happened was that the modem crashed while the AP was
> > > > in system suspend (or possibly even resuming) state.  And
> > > > there is no guarantee that the system will have called a
> > > > driver's ->resume callback when the crash notification is
> > > > delivered.
> > > >
> > > > In my case (in the IPA driver), handling a modem crash
> > > > cannot be done while the driver is suspended; i.e. the
> > > > activities in its ->resume callback must be completed
> > > > before we can recover from the crash.
> > > >
> > > > For this reason I might like to change the way the
> > > > crash notification is handled, but what I'd rather see
> > > > is to have the work queue not run until user space
> > > > is unfrozen, which would guarantee that all drivers
> > > > that have registered for a crash notification will
> > > > be resumed when the notification arrives.
> > > >
> > > > I'm not sure how that interacts with what you are
> > > > looking for here.  I think the workqueue could still
> > > > be unbound, but its work would be delayed longer before
> > > > any notification (and recovery) started.
> > > >
> > > >                     -Alex
> > > >
> > > >
> > > In that case, maybe adding a "WQ_FREEZABLE" flag might help?
> >
> > Yes, exactly.  But how does that affect whatever you were
> > trying to do with your patch?
>
> I don't see any impact on Rishabh's change in particular, syntactically
> it would just be a matter of adding another flag and the impact would 
> be
> separate from his patch.
>
> In other words, creating a separate work queue to get the long running
> work off the system_wq and making sure that these doesn't run during
> suspend & resume seems very reasonable to me.
>
> The one piece that I'm still contemplating is the HIPRIO, I would like
> to better understand the actual impact - or perhaps is this a result of
> everyone downstream moving all their work to HIPRIO work queues,
> starving the recovery?
Hi Bjorn,
You are right, this is a result of downstream having HIPRIO workqueues
therefore starving recovery. I don't have actual data to support the 
flag
as of now. If needed for now we can skip this flag and add it later with
sufficient data?
> Regards,
> Bjorn