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

[Tvrtko Ursulin]

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.kha...@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);