[PATCH v1 1/3] drm: function to get process name and pid

[Tvrtko Ursulin]

On 14/04/2025 18:58, Christian König wrote:
> Adding Pierre-eric and Tvrtko as well.

Thanks!

> Am 11.04.25 um 15:04 schrieb Sunil Khatri:
>> Add helper function which get the process information for
>> the drm_file and updates the user provided character buffer
>> with the information of process name and pid as a string.
>>
>> Signed-off-by: Sunil Khatri <sunil.khatri at amd.com>
>> ---
>>   drivers/gpu/drm/drm_file.c | 30 ++++++++++++++++++++++++++++++
>>   include/drm/drm_file.h     |  1 +
>>   2 files changed, 31 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>> index cb5f22f5bbb6..4434258d21b5 100644
>> --- a/drivers/gpu/drm/drm_file.c
>> +++ b/drivers/gpu/drm/drm_file.c
>> @@ -965,6 +965,36 @@ void drm_show_fdinfo(struct seq_file *m, struct file *f)
>>   }
>>   EXPORT_SYMBOL(drm_show_fdinfo);
>>   
>> +/**
>> + * drm_process_info - Fill info string with process name and pid
>> + * @file_priv: context of interest for process name and pid
>> + * @proc_info: user char ptr to write the string to
>> + * @buff_size: size of the buffer passed for the string
>> + *
>> + * This update the user provided buffer with process
>> + * name and pid information for @file_priv
>> + */
>> +void drm_process_info(struct drm_file *file_priv, char *proc_info, size_t buff_size)
>> +{
>> +	struct task_struct *task;
>> +	struct pid *pid;
>> +	struct drm_device *dev = file_priv->minor->dev;
>> +
>> +	if (!proc_info) {
>> +		drm_err(dev, "Invalid user buffer\n");

I'd replace this with drm_WARN_ON_ONCE.

Another thing I would consider is avoiding the need for stack space by 
exporting a logging helper instead. Something like (from patch 3/3):

drm_file_err(uq_mgr->file, "Timed out waiting for fence %p\n", f);

Which would output the client name info as a prefix or something.

Especially attractive if you add client name.

Also while here, is %p for the fence is useful? FWIW in the tracing 
series we are going for %llu:%llu (context:seqno).

Regards,

Tvrtko

>> +		return;
>> +	}
>> +
>> +	rcu_read_lock();
>> +	pid = rcu_dereference(file_priv->pid);
>> +	task = pid_task(pid, PIDTYPE_TGID);
>> +	if (task)
>> +		snprintf(proc_info, buff_size, "comm:%s pid:%d", task->comm, task->pid);
> 
> Looks good in general, but I think people would like to see the optional client name here as well.
> 
> It's rather useful to have for native context.
> 
> Regards,
> Christian.
> 
>> +
>> +	rcu_read_unlock();
>> +}
>> +EXPORT_SYMBOL(drm_process_info);
>> +
>>   /**
>>    * mock_drm_getfile - Create a new struct file for the drm device
>>    * @minor: drm minor to wrap (e.g. #drm_device.primary)
>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>> index f0ef32e9fa5e..c01b34936968 100644
>> --- a/include/drm/drm_file.h
>> +++ b/include/drm/drm_file.h
>> @@ -501,6 +501,7 @@ void drm_print_memory_stats(struct drm_printer *p,
>>   
>>   void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file);
>>   void drm_show_fdinfo(struct seq_file *m, struct file *f);
>> +void drm_process_info(struct drm_file *file_priv, char *proc_info, size_t buff_size);
>>   
>>   struct file *mock_drm_getfile(struct drm_minor *minor, unsigned int flags);
>>   
>