Re: [PATCH net] pds_core: Fix pdsc_check_pci_health function to print warning

[Simon Horman <horms@kernel.org>]

On Wed, Mar 20, 2024 at 11:39:54PM -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.
> 
> Unloading the driver in the fw_down/dead state uncovered another issue,
> which can be seen in the following trace:
> 
> WARNING: CPU: 51 PID: 6914 at kernel/workqueue.c:1450 __queue_work+0x358/0x440
> [...]
> RIP: 0010:__queue_work+0x358/0x440
> [...]
> Call Trace:
>  <TASK>
>  ? __warn+0x85/0x140
>  ? __queue_work+0x358/0x440
>  ? report_bug+0xfc/0x1e0
>  ? handle_bug+0x3f/0x70
>  ? exc_invalid_op+0x17/0x70
>  ? asm_exc_invalid_op+0x1a/0x20
>  ? __queue_work+0x358/0x440
>  queue_work_on+0x28/0x30
>  pdsc_devcmd_locked+0x96/0xe0 [pds_core]
>  pdsc_devcmd_reset+0x71/0xb0 [pds_core]
>  pdsc_teardown+0x51/0xe0 [pds_core]
>  pdsc_remove+0x106/0x200 [pds_core]
>  pci_device_remove+0x37/0xc0
>  device_release_driver_internal+0xae/0x140
>  driver_detach+0x48/0x90
>  bus_remove_driver+0x6d/0xf0
>  pci_unregister_driver+0x2e/0xa0
>  pdsc_cleanup_module+0x10/0x780 [pds_core]
>  __x64_sys_delete_module+0x142/0x2b0
>  ? syscall_trace_enter.isra.18+0x126/0x1a0
>  do_syscall_64+0x3b/0x90
>  entry_SYSCALL_64_after_hwframe+0x72/0xdc
> RIP: 0033:0x7fbd9d03a14b
> [...]
> 
> Fix this by preventing the devcmd reset if the FW is not running.
> 
> Fixes: d9407ff11809 ("pds_core: Prevent health thread from running during reset/remove")
> Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
> Signed-off-by: Brett Creeley <brett.creeley@amd.com>

Reviewed-by: Simon Horman <horms@kernel.org>