linux-kernel - Re: [PATCH v3 1/3] drm: Create an app info option for wedge events

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Message-ID: <aCpQaPzY0Vl5cl8T@black.fi.intel.com>
Date: Mon, 19 May 2025 00:26:00 +0300
From: Raag Jadav <raag.jadav@...el.com>
To: André Almeida <andrealmeid@...lia.com>
Cc: Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	siqueira@...lia.com, airlied@...il.com, simona@...ll.ch,
	rodrigo.vivi@...el.com, jani.nikula@...ux.intel.com,
	Xaver Hugl <xaver.hugl@...il.com>,
	"Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
	Krzysztof Karas <krzysztof.karas@...el.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	kernel-dev@...lia.com, amd-gfx@...ts.freedesktop.org,
	intel-xe@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v3 1/3] drm: Create an app info option for wedge events

On Mon, May 12, 2025 at 05:34:35PM -0300, André Almeida wrote:
> When a device get wedged, it might be caused by a guilty application.
> For userspace, knowing which app was the cause can be useful for some
> situations, like for implementing a policy, logs or for giving a chance
> for the compositor to let the user know what app caused the problem.
> This is an optional argument, when the app info is not available, the
> PID and APP string won't appear in the event string.
> 
> Sometimes just the PID isn't enough giving that the app might be already
> dead by the time userspace will try to check what was this PID's name,
> so to make the life easier also notify what's the app's name in the user
> event.

...

> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 3dc7acd56b1d..e30efa4ac330 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -542,6 +542,7 @@ static const char *drm_get_wedge_recovery(unsigned int opt)
>   * drm_dev_wedged_event - generate a device wedged uevent
>   * @dev: DRM device
>   * @method: method(s) to be used for recovery
> + * @info: optional information about the guilty app
>   *
>   * This generates a device wedged uevent for the DRM device specified by @dev.
>   * Recovery @method\(s) of choice will be sent in the uevent environment as
> @@ -554,13 +555,14 @@ static const char *drm_get_wedge_recovery(unsigned int opt)
>   *
>   * Returns: 0 on success, negative error code otherwise.
>   */
> -int drm_dev_wedged_event(struct drm_device *dev, unsigned long method)
> +int drm_dev_wedged_event(struct drm_device *dev, unsigned long method,
> +			 struct drm_wedge_app_info *info)
>  {
>  	const char *recovery = NULL;
>  	unsigned int len, opt;
>  	/* Event string length up to 28+ characters with available methods */
> -	char event_string[32];
> -	char *envp[] = { event_string, NULL };
> +	char event_string[32], pid_string[15] = "", comm_string[TASK_COMM_LEN] = "";

Let's make these into proper defines for consistency,

#define WEDGE_STR_LEN
#define PID_LEN

and drop redundant comment.

> +	char *envp[] = { event_string, NULL, NULL, NULL };
>  
>  	len = scnprintf(event_string, sizeof(event_string), "%s", "WEDGED=");
>  
> @@ -582,6 +584,13 @@ int drm_dev_wedged_event(struct drm_device *dev, unsigned long method)
>  	drm_info(dev, "device wedged, %s\n", method == DRM_WEDGE_RECOVERY_NONE ?
>  		 "but recovered through reset" : "needs recovery");
>  
> +	if (info) {
> +		snprintf(pid_string, sizeof(pid_string), "PID=%u", info->pid);
> +		snprintf(comm_string, sizeof(comm_string), "APP=%s", info->comm);

Since this is a core helper, we'd want to make sure these fields are valid
and not being abused.

Also s/APP/TASK IMHO, but upto you.

Raag