[PATCH] drm/xe/debugfs: fixed the return value of wedged_mode_set

[Rodrigo Vivi]

On Fri, Feb 14, 2025 at 06:36:15AM +0800, Xin Wang wrote:
> It is generally expected that the write() function should return a
> positive value indicating the number of bytes written or a negative
> error code if an error occurs. Returning 0 is unusual and can lead
> to unexpected behavior.
> 
> When the user program writes the same value to wedged_mode twice in
> a row, a lockup will occur, because the value expected to be
> returned by the write() function inside the program should be equal
> to the actual written value instead of 0.
> 
> To reproduce the issue:
> echo 1 > /sys/kernel/debug/dri/0/wedged_mode
> echo 1 > /sys/kernel/debug/dri/0/wedged_mode   <- lockup here
> 
> Signed-off-by: Xin Wang <x.wang at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Fei Yang <fei.yang at intel.com>
> Cc: Shuicheng Lin <shuicheng.lin at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_debugfs.c b/drivers/gpu/drm/xe/xe_debugfs.c
> index 56cb3788e752..b46075edf60a 100644
> --- a/drivers/gpu/drm/xe/xe_debugfs.c
> +++ b/drivers/gpu/drm/xe/xe_debugfs.c
> @@ -167,7 +167,7 @@ static ssize_t wedged_mode_set(struct file *f, const char __user *ubuf,
>  		return -EINVAL;
>  
>  	if (xe->wedged.mode == wedged_mode)
> -		return 0;
> +		return size;

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>

>  
>  	xe->wedged.mode = wedged_mode;
>  
> -- 
> 2.43.0
>