[PATCH v5 1/3] drm: Create a task info option for wedge events

[Raag Jadav]

On Tue, May 20, 2025 at 01:32:41PM -0300, André Almeida wrote:
> When a device get wedged, it might be caused by a guilty application.
> For userspace, knowing which task 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 task caused the problem.
> This is an optional argument, when the task info is not available, the
> PID and TASK string won't appear in the event string.
> 
> Sometimes just the PID isn't enough giving that the task 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 task's name in the user
> event.

...

> -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_task_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[WEDGE_STR_LEN], pid_string[PID_LEN] = "", comm_string[TASK_COMM_LEN] = "";
> +	char *envp[] = { event_string, NULL, NULL, NULL };
>  
>  	len = scnprintf(event_string, sizeof(event_string), "%s", "WEDGED=");
>  
> @@ -582,6 +586,13 @@ 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 && ((info->comm && info->comm[0] != '\0'))) {

Thanks for adding this. Should we check if pid > 0?

Also, I was wondering what if the driver only has info on one of the
given members? Should we allow it to be flagged independently?

> +		snprintf(pid_string, sizeof(pid_string), "PID=%u", info->pid);
> +		snprintf(comm_string, sizeof(comm_string), "TASK=%s", info->comm);
> +		envp[1] = pid_string;
> +		envp[2] = comm_string;
> +	}
> +
>  	return kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
>  }
>  EXPORT_SYMBOL(drm_dev_wedged_event);

...

> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index e2f894f1b90a..c13fe85210f2 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -30,6 +30,14 @@ struct pci_controller;
>  #define DRM_WEDGE_RECOVERY_REBIND	BIT(1)	/* unbind + bind driver */
>  #define DRM_WEDGE_RECOVERY_BUS_RESET	BIT(2)	/* unbind + reset bus device + bind */
>  
> +/**
> + * struct drm_wedge_task_info - information about the guilty app of a wedge dev

s/app/task, missed an instance ;)

> + */
> +struct drm_wedge_task_info {
> +	pid_t pid;
> +	char *comm;
> +};

Raag