linux-kernel - Re: [PATCH v8 09/24] ASoC: qdsp6: q6afe: Add q6afe driver

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Date:   Thu, 17 May 2018 18:53:42 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     andy.gross@...aro.org, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, robh+dt@...nel.org,
        bgoswami@...eaurora.org, gregkh@...uxfoundation.org,
        david.brown@...aro.org, mark.rutland@....com, lgirdwood@...il.com,
        plai@...eaurora.org, tiwai@...e.com, perex@...ex.cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, rohkumar@....qualcomm.com,
        spatakok@....qualcomm.com
Subject: Re: [PATCH v8 09/24] ASoC: qdsp6: q6afe: Add q6afe driver



On 17/05/18 18:23, Mark Brown wrote:
> On Thu, May 17, 2018 at 06:10:49PM +0100, Srinivas Kandagatla wrote:
>> On 17/05/18 07:55, Mark Brown wrote:
>>> On Wed, May 09, 2018 at 01:56:20PM +0100, Srinivas Kandagatla wrote:
> 
>>> This lock only protects the list, it does nothing to ensure that the
>>> port we look up is still valid by the time we return to the caller.
>>> That means we won't crash during list traversal but does nothing to
>>> ensure we won't crash immediately afterwards if the port is deallocated
>>> just after we look it up.  What stops that happening?
> 
>> Each port is allocated and de-allocated in dai probe and remove calls
>> respectively.
> 
>> Lets say... So for this case to happen the dai has to be removed (unload
>> module) at the same time when the interrupt callback happens due to delayed
>> response from previous commands.
> 
>> This case would be almost impossible because all the calls to afe service
>> are synchronous with timeouts, if any of the previous calls times out the
>> respective caller would get an error, this should prevent him from unloading
>> the module in the first place.
> 
> The user can also trigger manual unbinds without unloading the module,
> and to be honet the scenario where the DSP has stopped responding well
> and is delaying responses sounds like exactly the sort of time when
> users might try to reload the driver...Yes, that is one possible usecase!
ref-counting port should stop that from happening.
I will add this in next spin!

thanks,
srini