[net-next v1] net: wwan: t7xx: Fix FSM command timeout issue

[Mateusz Polchlopek]

On 12/12/2024 11:55 AM, Jinjian Song wrote:
> When driver processes the internal state change command, it use
> asynchronous thread to process the command operation. If the main
> thread detects that the task has timed out, the asynchronous thread
> will panic when executing te completion notification because the
> main thread completion object is released.
> 
> BUG: unable to handle page fault for address: fffffffffffffff8
> PGD 1f283a067 P4D 1f283a067 PUD 1f283c067 PMD 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> RIP: 0010:complete_all+0x3e/0xa0
> [...]
> Call Trace:
>   <TASK>
>   ? __die_body+0x68/0xb0
>   ? page_fault_oops+0x379/0x3e0
>   ? exc_page_fault+0x69/0xa0
>   ? asm_exc_page_fault+0x22/0x30
>   ? complete_all+0x3e/0xa0
>   fsm_main_thread+0xa3/0x9c0 [mtk_t7xx (HASH:1400 5)]
>   ? __pfx_autoremove_wake_function+0x10/0x10
>   kthread+0xd8/0x110
>   ? __pfx_fsm_main_thread+0x10/0x10 [mtk_t7xx (HASH:1400 5)]
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork+0x38/0x50
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork_asm+0x1b/0x30
>   </TASK>
> [...]
> CR2: fffffffffffffff8
> ---[ end trace 0000000000000000 ]---
> 
> After the main thread determines that the task has timed out, mark
> the completion invalid, and add judgment in the asynchronous task.
> 
> Signed-off-by: Jinjian Song <jinjian.song at fibocom.com>
> ---
>   drivers/net/wwan/t7xx/t7xx_state_monitor.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wwan/t7xx/t7xx_state_monitor.c b/drivers/net/wwan/t7xx/t7xx_state_monitor.c
> index 3931c7a13f5a..57f1a7730fff 100644
> --- a/drivers/net/wwan/t7xx/t7xx_state_monitor.c
> +++ b/drivers/net/wwan/t7xx/t7xx_state_monitor.c
> @@ -108,7 +108,8 @@ static void fsm_finish_command(struct t7xx_fsm_ctl *ctl, struct t7xx_fsm_command
>   {
>   	if (cmd->flag & FSM_CMD_FLAG_WAIT_FOR_COMPLETION) {
>   		*cmd->ret = result;
> -		complete_all(cmd->done);
> +		if (cmd->done)
> +			complete_all(cmd->done);
>   	}
>   
>   	kfree(cmd);
> @@ -503,8 +504,10 @@ int t7xx_fsm_append_cmd(struct t7xx_fsm_ctl *ctl, enum t7xx_fsm_cmd_state cmd_id
>   
>   		wait_ret = wait_for_completion_timeout(&done,
>   						       msecs_to_jiffies(FSM_CMD_TIMEOUT_MS));
> -		if (!wait_ret)
> +		if (!wait_ret) {
> +			cmd->done = NULL;
>   			return -ETIMEDOUT;
> +		}
>   
>   		return ret;
>   	}

If this is a fix then should be targeted to net and not net-next
and probably should have Fixes: tag.