netdev - Re: [PATCH v3 net 1/4] pds_core: Prevent possible adminq overflow/stuck condition

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Message-ID: <61b952ee-d4e4-4e1a-bee6-4bde45ec1025@intel.com>
Date: Wed, 16 Apr 2025 13:13:02 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Shannon Nelson <shannon.nelson@....com>, <andrew+netdev@...n.ch>,
	<brett.creeley@....com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <michal.swiatkowski@...ux.intel.com>,
	<horms@...nel.org>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 net 1/4] pds_core: Prevent possible adminq
 overflow/stuck condition



On 4/15/2025 4:29 PM, 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.
> 

What happens if a client driver tries to enqueue a request when the
adminq is full? Does it just block until there is space, presumably
holding the adminq_lock the entire time to prevent someone else from
inserting?