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

[Jani Nikula]

On Thu, 17 Apr 2025, Christian König <christian.koenig at amd.com> wrote:
> 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.

Please see the completely untested patch below for a starting point.

BR,
Jani.



>From 55968ab339467c5b6e12ceb157ecbaf62eaa6082 Mon Sep 17 00:00:00 2001
From: Sunil Khatri <sunil.khatri at amd.com>
Date: Thu, 17 Apr 2025 14:43:51 +0530
Subject: [PATCH] drm: add macro drm_file_err to print process info
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Cc: Jani Nikula <jani.nikula at intel.com>

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

Signed-off-by: Sunil Khatri <sunil.khatri at amd.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/drm_file.c | 45 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_file.h     |  3 +++
 2 files changed, 48 insertions(+)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index c299cd94d3f7..dea954f57890 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -1025,3 +1025,48 @@ struct file *mock_drm_getfile(struct drm_minor *minor, unsigned int flags)
 	return file;
 }
 EXPORT_SYMBOL_FOR_TESTS_ONLY(mock_drm_getfile);
+
+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)
+{
+	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
+ * @format: printf() like format string
+ *
+ * This update the user provided buffer with process
+ * name and pid information for @file_priv
+ */
+void drm_file_err(struct drm_file *file_priv, const char *format, ...)
+{
+	struct drm_device *dev = file_priv->minor->dev;
+	struct task_struct *task;
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, format);
+	vaf.fmt = format;
+	vaf.va = &args;
+
+	task = drm_task_lock(file_priv);
+	drm_err(dev, "comm: %s pid: %d client: %s %pV",
+		task ? task->comm : "", task ? task->pid : 0,
+		file_priv->client_name ?: "Unset", &vaf);
+	drm_task_unlock(file_priv);
+}
+EXPORT_SYMBOL(drm_file_err);
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 94d365b22505..ceb08a67f0b7 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -446,6 +446,9 @@ static inline bool drm_is_accel_client(const struct drm_file *file_priv)
 	return file_priv->minor->type == DRM_MINOR_ACCEL;
 }
 
+__printf(2, 3)
+void drm_file_err(struct drm_file *file_priv, const char *format, ...);
+
 void drm_file_update_pid(struct drm_file *);
 
 struct drm_minor *drm_minor_acquire(struct xarray *minors_xa, unsigned int minor_id);
-- 
2.39.5




-- 
Jani Nikula, Intel