Re: [PATCH v4 1/5] drm: add macro drm_file_err to print process info

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 17 Apr 2025, "Khatri, Sunil" <sukhatri@amd.com> wrote:
> On 4/16/2025 7:55 PM, Jani Nikula wrote:
>> On Wed, 16 Apr 2025, Sunil Khatri<sunil.khatri@amd.com> wrote:
>>> Add a drm helper macro which append the process information for
>>> the drm_file over drm_err.
>>>
>>> Signed-off-by: Sunil Khatri<sunil.khatri@amd.com>
>>> ---
>>>   include/drm/drm_file.h | 41 +++++++++++++++++++++++++++++++++++++++++
>>>   1 file changed, 41 insertions(+)
>>>
>>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>>> index 94d365b22505..5ae5ad1048fb 100644
>>> --- a/include/drm/drm_file.h
>>> +++ b/include/drm/drm_file.h
>>> @@ -37,6 +37,7 @@
>>>   #include <uapi/drm/drm.h>
>>>   
>>>   #include <drm/drm_prime.h>
>>> +#include <drm/drm_print.h>
>> Not a fan of including drm_print.h everywhere that drm_file.h is
>> included. We've been trying to get rid of this, and go the other
>> way. It's really hard to manage dependencies when everything ends up
>> including everything.
>>
>>>   
>>>   struct dma_fence;
>>>   struct drm_file;
>>> @@ -446,6 +447,46 @@ static inline bool drm_is_accel_client(const struct drm_file *file_priv)
>>>   	return file_priv->minor->type == DRM_MINOR_ACCEL;
>>>   }
>>>   
>>> +static struct task_struct *drm_task_lock(struct drm_file *file_priv)
>>> +					__attribute__((__maybe_unused));
>> inline is the keyword you're missing here, and that's why you've had to
>> add maybe unused...
>>
>>> +static 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 void drm_task_unlock(struct drm_file *file_priv) __attribute__((__maybe_unused));
>>> +static void drm_task_unlock(struct drm_file *file_priv)
>>> +{
>>> +	rcu_read_unlock();
>>> +	mutex_unlock(&file_priv->client_name_lock);
>>> +}
>> ...but *why* are you inlining these? To make this header self-contained,
>> I think you'd need to add maybe sched.h, pid.h, rcupdate.h, mutex.h, or
>> something. I consider static inlines actively harmful if they force you
>> to pull in a lot of other headers.
>
> Code readability and easy maintenance is the key to make these as 
> inline.

Oh, quite the opposite. Static inlines are a maintenance nightmare.

BR,
Jani.


> Also we are  keeping the logic function which gets the task with 
> locks in separate function then actually
>
> passing that in the drm_err as string.
>
>>
>>> +/**
>>> + * 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)
>>> +
>> For that matter, why is *this* inline? For debugs it makes a little more
>> sense when it adds the function, but drm_err() doesn't.
>>
>> Make all of these real functions, no need to include drm_print.h, and
>> everything is better.
>>
> Only reason of hacing drm_file_err as a macro as the variadic fmt and 
> args are not possible to pass without using local variables to make 
> strings of fmt and args separately and with macro to macro they Are 
> passed cleanly and no local variables needed. you can check V3 i guess 
> where this whole was an function only.
>
> Regards Sunil Khatri
>
>> BR,
>> Jani.
>>
>>>   void drm_file_update_pid(struct drm_file *);
>>>   
>>>   struct drm_minor *drm_minor_acquire(struct xarray *minors_xa, unsigned int minor_id);

-- 
Jani Nikula, Intel