linux-kernel - Re: [PATCH v7 2/5] drm: Create a task info option for wedge events

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Message-ID: <aE6oFOBbQ_3oRwtB@black.fi.intel.com>
Date: Sun, 15 Jun 2025 14:01:40 +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>,
	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 v7 2/5] drm: Create a task info option for wedge events

On Fri, Jun 13, 2025 at 03:43:45PM -0300, André Almeida wrote:
> When a device get wedged, it might be caused by a guilty application.
> For userspace, knowing which task was involved 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 was involved in 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.
> 
> Acked-by: Rodrigo Vivi <rodrigo.vivi@...el.com> (for i915 and xe)
> Reviewed-by: Krzysztof Karas <krzysztof.karas@...el.com>
> Reviewed-by: Raag Jadav <raag.jadav@...el.com>

Although I'm okay with this version, a few aesthetic nits below.

> Signed-off-by: André Almeida <andrealmeid@...lia.com>

...

> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 56dd61f8e05a..eba99a081ec1 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -538,10 +538,15 @@ static const char *drm_get_wedge_recovery(unsigned int opt)
>  	}
>  }
>  
> +#define WEDGE_STR_LEN 32
> +#define PID_STR_LEN 15
> +#define COMM_STR_LEN (TASK_COMM_LEN + 5)

Align the values using tabs for readability, and since you're using
TASK_COMM_LEN here please include sched.h instead of relying on
intermediate header which may not guarantee it for other archs and
randconfigs.

> +
>  /**
>   * 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 task
>   *
>   * 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 +559,13 @@ 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_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_STR_LEN], comm_string[COMM_STR_LEN];
> +	char *envp[] = { event_string, NULL, NULL, NULL };

Let's make this reverse xmas order and be consistent with other helpers
in this file.

>  	len = scnprintf(event_string, sizeof(event_string), "%s", "WEDGED=");
>  
> @@ -582,6 +587,13 @@ 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[0] != '\0') && (info->pid >= 0)) {
> +		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..729e1c6da138 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 task of a wedge dev
> + */
> +struct drm_wedge_task_info {
> +	pid_t pid;
> +	char comm[TASK_COMM_LEN];

Ditto for sched.h.

Raag

> +};
> +
>  /**
>   * enum switch_power_state - power state of drm device
>   */
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 63b51942d606..3f76a32d6b84 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -487,7 +487,8 @@ void drm_put_dev(struct drm_device *dev);
>  bool drm_dev_enter(struct drm_device *dev, int *idx);
>  void drm_dev_exit(int idx);
>  void drm_dev_unplug(struct drm_device *dev);
> -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);
>  
>  /**
>   * drm_dev_is_unplugged - is a DRM device unplugged
> -- 
> 2.49.0
>