Re: [PATCH] qed: fix possible unpaired spin_{un}lock_bh in _qed_mcp_cmd_and_union()

[Prabhakar Kushwaha]

Hi Jia,

On Thu, Jul 15, 2021 at 2:28 PM Jia He <justin.he@xxxxxxx> wrote:
>
> Liajian reported a bug_on hit on a ThunderX2 arm64 server with FastLinQ
> QL41000 ethernet controller:
>  BUG: scheduling while atomic: kworker/0:4/531/0x00000200
>   [qed_probe:488()]hw prepare failed
>   kernel BUG at mm/vmalloc.c:2355!
>   Internal error: Oops - BUG: 0 [#1] SMP
>   CPU: 0 PID: 531 Comm: kworker/0:4 Tainted: G W 5.4.0-77-generic #86-Ubuntu
>   pstate: 00400009 (nzcv daif +PAN -UAO)
>  Call trace:
>   vunmap+0x4c/0x50
>   iounmap+0x48/0x58
>   qed_free_pci+0x60/0x80 [qed]
>   qed_probe+0x35c/0x688 [qed]
>   __qede_probe+0x88/0x5c8 [qede]
>   qede_probe+0x60/0xe0 [qede]
>   local_pci_probe+0x48/0xa0
>   work_for_cpu_fn+0x24/0x38
>   process_one_work+0x1d0/0x468
>   worker_thread+0x238/0x4e0
>   kthread+0xf0/0x118
>   ret_from_fork+0x10/0x18
>
> In this case, qed_hw_prepare() returns error due to hw/fw error, but in
> theory work queue should be in process context instead of interrupt.
>
> The root cause might be the unpaired spin_{un}lock_bh() in
> _qed_mcp_cmd_and_union(), which causes botton half is disabled incorrectly.
>
> Reported-by: Lijian Zhang <Lijian.Zhang@xxxxxxx>
> Signed-off-by: Jia He <justin.he@xxxxxxx>
> ---

This patch is adding additional spin_{un}lock_bh().
Can you please enlighten about the exact flow causing this unpaired
spin_{un}lock_bh.

Also,
as per description, looks like you are not sure actual the root-cause.
does this patch really solved the problem?

--pk