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

["André Almeida" <andrealmeid@igalia.com>]

Em 21/05/2025 06:11, Raag Jadav escreveu:
> 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?
> 

Ack, added this for the v6.

> 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?

I think we can allow it, but for now I would say that we can wait for a 
driver that works like that to settle that.

> 
>> +		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
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