[PATCH v6 1/5] drm: add macro drm_file_err to print process info

[Christian König]

Am 17.04.25 um 13:07 schrieb Jani Nikula:
> On Thu, 17 Apr 2025, Christian König <christian.koenig at amd.com> wrote:
>> Am 17.04.25 um 11:35 schrieb Jani Nikula:
>>> On Thu, 17 Apr 2025, Sunil Khatri <sunil.khatri at amd.com> wrote:
>>>> Add a drm helper macro which append the process information for
>>>> the drm_file over drm_err.
>>>>
>>>> v5: change to macro from function (Christian Koenig)
>>>>     add helper functions for lock/unlock (Christian Koenig)
>>>>
>>>> v6: remove __maybe_unused and make function inline (Jani Nikula)
>>>>     remove drm_print.h
>>> I guess I gave all kinds of comments, but in the end my conclusion was:
>>> why does *any* of this have to be static inline or macros? Make
>>> drm_file_err() a regular function and hide the implementation inside
>>> drm_file.c. That's the cleanest approach IMO.
>> That won't work. The macro is necessary to concatenate the format strings.
> I think you can handle them using struct va_format and %pV.

Oh, really good point! I wasn't aware that this functionality exists.

Going to discuss that with Sunil internally.

Thanks,
Christian.

>
> BR,
> Jani.
>
>
>> But the drm_task_lock() and drm_task_unlock() functions shouldn't be in the header. Those can be perfectly in drm_file.c or drm_print.c
>>
>> And we should put drm_file_err into drm_print.h instead of drm_file.h as far as I can see.
>>
>> Regards,
>> Christian.
>>
>>> BR,
>>> Jani.
>>>
>>>> Signed-off-by: Sunil Khatri <sunil.khatri at amd.com>
>>>> ---
>>>>  include/drm/drm_file.h | 37 +++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 37 insertions(+)
>>>>
>>>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>>>> index 94d365b22505..856b38e996c7 100644
>>>> --- a/include/drm/drm_file.h
>>>> +++ b/include/drm/drm_file.h
>>>> @@ -446,6 +446,43 @@ static inline bool drm_is_accel_client(const struct drm_file *file_priv)
>>>>  	return file_priv->minor->type == DRM_MINOR_ACCEL;
>>>>  }
>>>>  
>>>> +static inline struct task_struct *drm_task_lock(struct drm_file *file_priv)
>>>> +{
>>>> +	struct task_struct *task;
>>>> +	struct pid *pid;
>>>> +
>>>> +	mutex_lock(&file_priv->client_name_lock);
>>>> +	rcu_read_lock();
>>>> +	pid = rcu_dereference(file_priv->pid);
>>>> +	task = pid_task(pid, PIDTYPE_TGID);
>>>> +	return task;
>>>> +}
>>>> +
>>>> +static inline void drm_task_unlock(struct drm_file *file_priv)
>>>> +{
>>>> +	rcu_read_unlock();
>>>> +	mutex_unlock(&file_priv->client_name_lock);
>>>> +}
>>>> +/**
>>>> + * drm_file_err - Fill info string with process name and pid
>>>> + * @file_priv: context of interest for process name and pid
>>>> + * @fmt: prinf() like format string
>>>> + *
>>>> + * This update the user provided buffer with process
>>>> + * name and pid information for @file_priv
>>>> + */
>>>> +#define drm_file_err(file_priv, fmt, ...)						\
>>>> +	do {										\
>>>> +		struct task_struct *task;						\
>>>> +		struct drm_device *dev = file_priv->minor->dev;				\
>>>> +											\
>>>> +		task = drm_task_lock(file_priv);					\
>>>> +		drm_err(dev, "comm: %s pid: %d client: %s " fmt,			\
>>>> +			task ? task->comm : "", task ? task->pid : 0,			\
>>>> +			file_priv->client_name ?: "Unset", ##__VA_ARGS__);		\
>>>> +		drm_task_unlock(file_priv);						\
>>>> +	} while (0)
>>>> +
>>>>  void drm_file_update_pid(struct drm_file *);
>>>>  
>>>>  struct drm_minor *drm_minor_acquire(struct xarray *minors_xa, unsigned int minor_id);