linux-kernel - Re: [PATCH v4 3/5] remoteproc: Pass type of shutdown to subdev remove

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Date:   Tue, 5 Dec 2017 11:54:45 +0100
From:   Arnaud Pouliquen <arnaud.pouliquen@...com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     Andy Gross <andy.gross@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Arun Kumar Neelakantam <aneela@...eaurora.org>,
        Chris Lew <clew@...eaurora.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-soc@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] remoteproc: Pass type of shutdown to subdev remove



On 12/05/2017 07:46 AM, Bjorn Andersson wrote:
> On Fri 01 Dec 06:50 PST 2017, Arnaud Pouliquen wrote:
> 
>> hello Bjorn,
>>
>> Sorry for these late remarks/questions
>>
> 
> No worries, I'm happy to see you reading the patch!
> 
>>
>> On 11/30/2017 02:16 AM, Bjorn Andersson wrote:
> [..]
>>> diff --git a/drivers/remoteproc/qcom_common.c b/drivers/remoteproc/qcom_common.c
> [..]
>>> @@ -785,17 +785,17 @@ static int rproc_probe_subdevices(struct rproc *rproc)
>>>  
>>>  unroll_registration:
>>>  	list_for_each_entry_continue_reverse(subdev, &rproc->subdevs, node)
>>> -		subdev->remove(subdev);
>>> +		subdev->remove(subdev, false);
>> Why do you need to do a non graceful remove in this case? This could
>> lead to side effect like memory leakage...
>>
> 
> Regardless of this being true or false resources should always be
> reclaimed.
> 
> The reason for introducing this is that the modem in the Qualcomm
> platforms implements persistent storage and it's preferred to tell it to
> flush the latest data to the storage server (on the Linux side) before
> pulling the plug. But in the case of a firmware crash this mechanism
> will not be operational and there's no point in attempting this
> "graceful shutdown".
I understand your usecase for Qualcomm, but in rproc_probe_subdevices
there is not crash of the remote firmware , so remove should be graceful.

> 
> [..]
>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>> index 44e630eb3d94..20a9467744ea 100644
>>> --- a/include/linux/remoteproc.h
>>> +++ b/include/linux/remoteproc.h
>>> @@ -456,7 +456,7 @@ struct rproc_subdev {
>>>  	struct list_head node;
>>>  
>>>  	int (*probe)(struct rproc_subdev *subdev);
>>> -	void (*remove)(struct rproc_subdev *subdev);
>>> +	void (*remove)(struct rproc_subdev *subdev, bool graceful);
>> What about adding a new ops instead of a parameter, like a recovery
>> callback?
>>
> 
> I think that for symmetry purposes it should be probe/remove in both
> code paths. A possible alternative to the proposal would be to introduce
> an operation "request_shutdown()" the would be called in the proposed
> graceful code path.
> 
> 
> However, in the Qualcomm SMD and GLINK (conceptually equivalent to
> virtio-rpmsg) it is possible to open and close communication channels
> and it's conceivable to see that the graceful case would close all
> channels cleanly while the non-graceful case would just remove the rpmsg
> devices (and leave the channel states/memory as is).
> 
> In this case a "request_shutdown()" would complicate things, compared to
> the boolean.
> 
I would be more for a specific ops that inform sub-dev on a crash. This
would allow sub-dev to perform specific action (for instance dump) and
store crash information, then on remove, sub_dev would perform specific
action.
This could be something like "trigger_recovery" that is propagated to
the sub-dev.

That would sound more flexible from my point of view.

Regards
Arnaud
> Regards,
> Bjorn
>