Re: [PATCH v3 1/4] drm: add function drm_file_err to print proc information too

[Tvrtko Ursulin <tvrtko.ursulin@igalia.com>]

On 15/04/2025 19:43, Sunil Khatri wrote:
> Add a drm helper function which get the process information for
> the drm_file and append the process information using the existing
> drm_err.
> 
> Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
> ---
>   include/drm/drm_file.h | 40 ++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 40 insertions(+)
> 
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 94d365b22505..e329299a2b2c 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>
>   
>   struct dma_fence;
>   struct drm_file;
> @@ -446,6 +447,45 @@ static inline bool drm_is_accel_client(const struct drm_file *file_priv)
>   	return file_priv->minor->type == DRM_MINOR_ACCEL;
>   }
>   
> +/**
> + * 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
> + */
> +__printf(2, 3)
> +static inline void drm_file_err(struct drm_file *file_priv, const char *fmt, ...)
> +{
> +	struct task_struct *task;
> +	struct pid *pid;
> +	struct drm_device *dev = file_priv->minor->dev;
> +	char new_fmt[256];
> +	char final_fmt[512];
> +	va_list args;
> +
> +	mutex_lock(&file_priv->client_name_lock);
> +	rcu_read_lock();
> +	pid = rcu_dereference(file_priv->pid);
> +	task = pid_task(pid, PIDTYPE_TGID);
> +
> +	if (drm_WARN_ON_ONCE(dev, !task))
> +		return;
> +
> +	snprintf(new_fmt, sizeof(new_fmt), "proc:%s pid:%d client_name:%s %s",
> +		task->comm, task->pid, file_priv->client_name ?: "Unset", fmt);
> +
> +	va_start(args, fmt);
> +	vsnprintf(final_fmt, sizeof(final_fmt), new_fmt, args);
> +
> +	drm_err(dev, "%s", final_fmt);
> +	va_end(args);
> +
> +	rcu_read_unlock();
> +	mutex_unlock(&file_priv->client_name_lock);
> +}
> +

I was hoping something primitive could be enough. With no temporary 
stack space required. Primitive on the level of (but simplified for 
illustration purpose):

#define some_err(_file, _fmt, ...) \
	drm_err(dev, "client-%s: " _fmt, (_this)->client_name, ##__VA_ARGS__)

Am I missing something or that would work?

Regards,

Tvrtko

>   void drm_file_update_pid(struct drm_file *);
>   
>   struct drm_minor *drm_minor_acquire(struct xarray *minors_xa, unsigned int minor_id);