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

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Date: Fri, 22 Mar 2024 18:02:51 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: 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 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.