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

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Date:   Thu, 17 Dec 2020 12:49:17 -0600
From:   Alex Elder <elder@...aro.org>
To:     rishabhb@...eaurora.org
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        tsoni@...eaurora.org, psodagud@...eaurora.org,
        sidgup@...eaurora.org
Subject: Re: [PATCH] remoteproc: Create a separate workqueue for recovery
 tasks

On 12/17/20 12:21 PM, rishabhb@...eaurora.org 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?

					-Alex

. . .