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

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Date: Sat, 15 Jun 2024 01:49:34 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <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 6/14/24 13:54, Krzysztof Kozlowski wrote:
> 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.

Didn't I go further and say I got it tested though? Also can you
elaborate on what race do you think the bwmon will hit rather than
being too generic about it?

-Sibi

> 
> Best regards,
> Krzysztof
>