linux-kernel - Re: [PATCH 2/4] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances

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Date: Fri, 14 Jun 2024 10:24:14 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Sibi Sankar <quic_sibis@...cinc.com>, andersson@...nel.org,
 konrad.dybcio@...aro.org, djakov@...nel.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, srinivas.kandagatla@...aro.org
Cc: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
 quic_rgottimu@...cinc.com, quic_kshivnan@...cinc.com, conor+dt@...nel.org,
 dmitry.baryshkov@...aro.org, abel.vesa@...aro.org
Subject: Re: [PATCH 2/4] soc: qcom: icc-bwmon: Allow for interrupts to be
 shared across instances

On 13/06/2024 19:02, Sibi Sankar wrote:
> 
> 
> On 6/4/24 12:16, Krzysztof Kozlowski wrote:
>> On 04/06/2024 03:11, Sibi Sankar wrote:
>>> The multiple BWMONv4 instances available on the X1E80100 SoC use the
>>> same interrupt number. Mark them are shared to allow for re-use across
>>> instances.
> 
> Hey Krzysztof,
> 
> Thanks for taking time to review the series :)
> 
>>
>> Would be nice if you also mention you checked that it is safe to have
>> both devm and shared interrupts (so you investigated possibility of race
>> on exit path).
> 
> I didn't see any problems with devm being used with SHARED when I posted
> it out. After your review comments I went back again to vett the exit
> path for races and ran into an pre-existing splat [1] but the bwmon
> instances work as expected on module removal/re-insertion.

Using devm and shared interrupts is in general sign of possible race
issues and should be avoided. Just "not seeing problems" is not an
argument for me, to be honest.

Best regards,
Krzysztof