netdev - Re: [PATCH net 2/2] pds_core: Add a retry mechanism when the adminq is full

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Message-ID: <20250129190326.456680c8@kernel.org>
Date: Wed, 29 Jan 2025 19:03:26 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Shannon Nelson <shannon.nelson@....com>
Cc: <netdev@...r.kernel.org>, <davem@...emloft.net>,
 <andrew+netdev@...n.ch>, <edumazet@...gle.com>, <pabeni@...hat.com>,
 <brett.creeley@....com>
Subject: Re: [PATCH net 2/2] pds_core: Add a retry mechanism when the adminq
 is full

On Tue, 28 Jan 2025 16:43:37 -0800 Shannon Nelson wrote:
> If the adminq is full, the driver reports failure when trying to post
> new adminq commands. This is a bit aggressive and unexpected because
> technically the adminq post didn't fail in this case, it was just full.
> To harden this path add support for a bounded retry mechanism.
> 
> It's possible some commands take longer than expected, maybe hundreds
> of milliseconds or seconds due to other processing on the device side,
> so to further reduce the chance of failure due to adminq full increase
> the PDS_CORE_DEVCMD_TIMEOUT from 5 to 10 seconds.
> 
> The caller of pdsc_adminq_post() may still see -EAGAIN reported if the
> space in the adminq never freed up. In this case they can choose to
> call the function again or fail. For now, no callers will retry.

How about a semaphore? You can initialize it to the number of slots
in the queue, and use down_timeout() if you want the 10 sec timeout?