drm/i915: Hold struct_mutex for per-file stats in debugfs/i915_gem_object

As we walk the obj->vma_list in per_file_stats(), we need to hold
struct_mutex to prevent alteration of that list.

Fixes: 1d2ac403ae3b ("drm: Protect dev->filelist with its own mutex")
Fixes: c84455b4bacc ("drm/i915: Move debug only per-request pid tracking from request to ctx")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101460
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170617115744.4452-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 1f1176b6400e5b43cc3c5b9d1e01285cf91d2f6a..f7aa6cbe3a2eef1e306176a271d892c2dfaef4ff 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -292,6 +292,8 @@ static int per_file_stats(int id, void *ptr, void *data)
        struct file_stats *stats = data;
        struct i915_vma *vma;
 
+       lockdep_assert_held(&obj->base.dev->struct_mutex);
+
        stats->count++;
        stats->total += obj->base.size;
        if (!obj->bind_count)
@@ -476,6 +478,8 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
                struct drm_i915_gem_request *request;
                struct task_struct *task;
 
+               mutex_lock(&dev->struct_mutex);
+
                memset(&stats, 0, sizeof(stats));
                stats.file_priv = file->driver_priv;
                spin_lock(&file->table_lock);
@@ -487,7 +491,6 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
                 * still alive (e.g. get_pid(current) => fork() => exit()).
                 * Therefore, we need to protect this ->comm access using RCU.
                 */
-               mutex_lock(&dev->struct_mutex);
                request = list_first_entry_or_null(&file_priv->mm.request_list,
                                                   struct drm_i915_gem_request,
                                                   client_link);
@@ -497,6 +500,7 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
                                PIDTYPE_PID);
                print_file_stats(m, task ? task->comm : "<unknown>", stats);
                rcu_read_unlock();
+
                mutex_unlock(&dev->struct_mutex);
        }
        mutex_unlock(&dev->filelist_mutex);