drm: Include task->name and master status in debugfs clients info

Showing who is the current master is useful for trying to decypher
errors when trying to acquire master (e.g. a race with X taking over
from plymouth). By including the process name as well as the pid
simplifies the task of grabbing enough information remotely at the point
of error.

v2: Add the command column header and flesh out a couple of comments.
(David Herrmann)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_info.c b/drivers/gpu/drm/drm_info.c
index 3c99f6f..d1c5904 100644 (file)
--- a/drivers/gpu/drm/drm_info.c
+++ b/drivers/gpu/drm/drm_info.c
@@ -183,15 +183,32 @@ int drm_clients_info(struct seq_file *m, void *data)
        struct drm_device *dev = node->minor->dev;
        struct drm_file *priv;
 
+       seq_printf(m,
+                  "%20s %5s %3s master a %5s %10s\n",
+                  "command",
+                  "pid",
+                  "dev",
+                  "uid",
+                  "magic");
+
+       /* dev->filelist is sorted youngest first, but we want to present
+        * oldest first (i.e. kernel, servers, clients), so walk backwardss.
+        */
        mutex_lock(&dev->struct_mutex);
-       seq_printf(m, "a dev    pid    uid      magic\n\n");
-       list_for_each_entry(priv, &dev->filelist, lhead) {
-               seq_printf(m, "%c %3d %5d %5d %10u\n",
-                          priv->authenticated ? 'y' : 'n',
-                          priv->minor->index,
+       list_for_each_entry_reverse(priv, &dev->filelist, lhead) {
+               struct task_struct *task;
+
+               rcu_read_lock(); /* locks pid_task()->comm */
+               task = pid_task(priv->pid, PIDTYPE_PID);
+               seq_printf(m, "%20s %5d %3d   %c    %c %5d %10u\n",
+                          task ? task->comm : "<unknown>",
                           pid_vnr(priv->pid),
+                          priv->minor->index,
+                          priv->is_master ? 'y' : 'n',
+                          priv->authenticated ? 'y' : 'n',
                           from_kuid_munged(seq_user_ns(m), priv->uid),
                           priv->magic);
+               rcu_read_unlock();
        }
        mutex_unlock(&dev->struct_mutex);
        return 0;