netdev - Re: [PATCH net 1/6] pds_core: Prevent possible adminq overflow/stuck condition

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Message-ID: <15f8ff56-0359-450b-9fa3-cbb57781985b@amd.com>
Date: Wed, 9 Apr 2025 16:32:26 -0700
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Simon Horman <horms@...nel.org>
Cc: andrew+netdev@...n.ch, brett.creeley@....com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 michal.swiatkowski@...ux.intel.com, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net 1/6] pds_core: Prevent possible adminq overflow/stuck
 condition

On 4/9/2025 2:37 AM, Simon Horman wrote:
> 
> On Mon, Apr 07, 2025 at 03:51:08PM -0700, Shannon Nelson wrote:
>> From: Brett Creeley <brett.creeley@....com>
>>
>> The pds_core's adminq is protected by the adminq_lock, which prevents
>> more than 1 command to be posted onto it at any one time. This makes it
>> so the client drivers cannot simultaneously post adminq commands.
>> However, the completions happen in a different context, which means
>> multiple adminq commands can be posted sequentially and all waiting
>> on completion.
>>
>> On the FW side, the backing adminq request queue is only 16 entries
>> long and the retry mechanism and/or overflow/stuck prevention is
>> lacking. This can cause the adminq to get stuck, so commands are no
>> longer processed and completions are no longer sent by the FW.
>>
>> As an initial fix, prevent more than 16 outstanding adminq commands so
>> there's no way to cause the adminq from getting stuck. This works
>> because the backing adminq request queue will never have more than 16
>> pending adminq commands, so it will never overflow. This is done by
>> reducing the adminq depth to 16.
>>
>> Fixes: 792d36ccc163 ("pds_core: Clean up init/uninit flows to be more readable")
> 
> Hi Brett and Shannon,
> 
> I see that the cited commit added the lines that are being updated
> to pdsc_core_init(). But it seems to me that it did so by moving
> them from pdsc_setup(). So I wonder if it is actually the commit
> that added the code to pdsc_setup() that is being fixed.
> 
> If so, perhaps:
> 
>    Fixes: 45d76f492938 ("pds_core: set up device and adminq")

Perhaps... is it better to call out the older commit even tho' lines 
have moved around and this possibly won't apply?

sln

> 
>> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
>> Signed-off-by: Brett Creeley <brett.creeley@....com>
>> Signed-off-by: Shannon Nelson <shannon.nelson@....com>
> 
> ...