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

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

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.

> +/**
> + * 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.

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