linux-kernel - Re: [PATCH net] pds_core: Fix pdsc_check_pci

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Message-ID: <29bc2adb-07d5-416d-b357-4cf084b45ed8@amd.com>
Date: Tue, 2 Apr 2024 10:02:57 -0700
From: Brett Creeley <bcreeley@....com>
To: Jakub Kicinski <kuba@...nel.org>, Brett Creeley <brett.creeley@....com>
Cc: davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, shannon.nelson@....com
Subject: Re: [PATCH net] pds_core: Fix pdsc_check_pci_health function to print
 warning

On 3/22/2024 6:02 PM, Jakub Kicinski wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> On Wed, 20 Mar 2024 23:39:54 -0700 Brett Creeley wrote:
>> When the driver notices fw_status == 0xff it tries to perform a PCI
>> reset on itself via pci_reset_function() in the context of the driver's
>> health thread. However, pdsc_reset_prepare calls
>> pdsc_stop_health_thread(), which attempts to stop/flush the health
>> thread. This results in a deadlock because the stop/flush will never
>> complete since the driver called pci_reset_function() from the health
>> thread context. Fix this by changing the pdsc_check_pci_health_function()
>> to print a dev_warn() once every fw_down/fw_up cycle and requiring the
>> user to perform a reset on the device via sysfs's reset interface,
>> reloading the driver, rebinding the device, etc.
> 
> Dunno, to call PCI reset you don't need much device context.
> Perhaps you could allocate a work entry, throw it onto a per-driver
> workqueue, and return. Basically some minimal viable way to
> "asynchronously" call pci_reset_function()?
> You can take a ref on the device so it doesn't disappear.
> And flush that queue on module unload.

Hi Jakub,

Yeah, this is better than my proposed solution. Now that I'm back from 
vacation I will work on a v2.

Thanks for the review,

Brett