linux-kernel - Re: [PATCH V2] rpmsg: glink: Add abort

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Message-ID: <ZvQ2lnRO/dTyH1g3@hu-bjorande-lv.qualcomm.com>
Date: Wed, 25 Sep 2024 09:13:10 -0700
From: Bjorn Andersson <quic_bjorande@...cinc.com>
To: Deepak Kumar Singh <quic_deesin@...cinc.com>
CC: <andersson@...nel.org>, <quic_clew@...cinc.com>,
        <mathieu.poirier@...aro.org>, <linux-kernel@...r.kernel.org>,
        <quic_sarannya@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH V2] rpmsg: glink: Add abort_tx check in intent wait

On Wed, Sep 25, 2024 at 12:53:28PM +0530, Deepak Kumar Singh wrote:
> From: Sarannya S <quic_sarannya@...cinc.com>
> 
> On remote susbsystem restart rproc will stop glink subdev which will

"When stopping or restarting a remoteproc the glink subdev stop will
invoke qcom_glink_native_remove(). Any ..."

> trigger qcom_glink_native_remove, any ongoing intent wait should be

Please always have () on function names, to make clear they are indeed
functions.

s/intent wait/wait for intent request/

And I think "can" is a better word than "should" (we can abort the wait
to not waiting for the intents that aren't expected to come).

> aborted from there otherwise this wait delays glink send which potentially
> delays glink channel removal as well. This further introduces delay in ssr
> notification to other remote subsystems from rproc.
> 
> Currently qcom_glink_native_remove is not setting channel->intent_received,

This observation is correct, but I don't see a reason why it should. So
express this in terms of the applicable logic (i.e. we have abort_tx to
signal this scenario already, let's use it)

> so any ongoing intent wait is not aborted on remote susbsystem restart.
> abort_tx flag can be used as a condition to abort in such cases.
> 
> Adding abort_tx flag check in intent wait, to abort intent wait from
> qcom_glink_native_remove.

More () please.

> 
> Fixes: c05dfce0b89e ("rpmsg: glink: Wait for intent, not just request ack")
> Cc: stable@...r.kernel.org

I don't think the current code is broken, just suboptimal. And as such I
don't think this is a bugfix.

Perhaps I'm missing some case here? Otherwise, please drop the Fixes and
Cc...

> Signed-off-by: Sarannya S <quic_sarannya@...cinc.com>
> Signed-off-by: Deepak Kumar Singh <quic_deesin@...cinc.com>
> ---
>  drivers/rpmsg/qcom_glink_native.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 82d460ff4777..ff828531c36f 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -438,7 +438,6 @@ static void qcom_glink_handle_intent_req_ack(struct qcom_glink *glink,
>  
>  static void qcom_glink_intent_req_abort(struct glink_channel *channel)
>  {
> -	WRITE_ONCE(channel->intent_req_result, 0);
>  	wake_up_all(&channel->intent_req_wq);
>  }
>  
> @@ -1354,8 +1353,9 @@ static int qcom_glink_request_intent(struct qcom_glink *glink,
>  		goto unlock;
>  
>  	ret = wait_event_timeout(channel->intent_req_wq,
> -				 READ_ONCE(channel->intent_req_result) >= 0 &&
> -				 READ_ONCE(channel->intent_received),
> +				 (READ_ONCE(channel->intent_req_result) >= 0 &&
> +				 READ_ONCE(channel->intent_received)) ||
> +				 glink->abort_tx,

This looks good. But Chris and I talked about his patches posted
yesterday, and it seems like a good idea to differentiate the cases of
aborted and granted = 0.

Chris' patch is fixing a real bug, so that should be backported, so
let's conclude that discussion (with this patch included or in mind).

Regards,
Bjorn

>  				 10 * HZ);
>  	if (!ret) {
>  		dev_err(glink->dev, "intent request timed out\n");
> -- 
> 2.34.1
>