linux-kernel - Re: [PATCH 2/3] remoteproc: qcom_q6v5: Avoid handling handover twice

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Message-ID: <aKSSqXV5FOW27VJo@linaro.org>
Date: Tue, 19 Aug 2025 17:05:13 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Sibi Sankar <quic_sibis@...cinc.com>,
	Abel Vesa <abel.vesa@...aro.org>, linux-arm-msm@...r.kernel.org,
	linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH 2/3] remoteproc: qcom_q6v5: Avoid handling handover twice

On Tue, Aug 19, 2025 at 02:41:55PM +0300, Dmitry Baryshkov wrote:
> On Tue, Aug 19, 2025 at 01:08:03PM +0200, Stephan Gerhold wrote:
> > A remoteproc could theoretically signal handover twice. This is unexpected
> 
> theoretically or practically?
> 

You could easily trigger handover again from a custom remoteproc
firmware by setting the handover state to 0 and then back to 1. However,
if you find a firmware version doing this, you might want to have a
serious conversation with the firmware developer. It makes no sense to
do that. :-)

In other words, on technical level it is practical. From a conceptual
point of view it is just theoretical.

In any case, if it happens, we shouldn't mess up reference counters in
my opinion (or risk dereferencing invalid pointers etc).

Thanks,
Stephan