drm: Protect dev->filelist with its own mutex

amdgpu gained dev->struct_mutex usage, and that's because it's walking
the dev->filelist list. Protect that list with it's own lock to take
one more step towards getting rid of struct_mutex usage in drivers
once and for all.

While doing the conversion I noticed that 2 debugfs files in i915
completely lacked appropriate locking. Fix that up too.

v2: don't forget to switch to drm_gem_object_unreference_unlocked.

Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461691808-12414-9-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

@@ -93,7 +93,7 @@ void amdgpu_gem_force_release(struct amdgpu_device *adev)
 	struct drm_device *ddev = adev->ddev;
 	struct drm_file *file;
 
-	mutex_lock(&ddev->struct_mutex);
+	mutex_lock(&ddev->filelist_mutex);
 
 	list_for_each_entry(file, &ddev->filelist, lhead) {
 		struct drm_gem_object *gobj;
@@ -103,13 +103,13 @@ void amdgpu_gem_force_release(struct amdgpu_device *adev)
 		spin_lock(&file->table_lock);
 		idr_for_each_entry(&file->object_idr, gobj, handle) {
 			WARN_ONCE(1, "And also active allocations!\n");
-			drm_gem_object_unreference(gobj);
+			drm_gem_object_unreference_unlocked(gobj);
 		}
 		idr_destroy(&file->object_idr);
 		spin_unlock(&file->table_lock);
 	}
 
-	mutex_unlock(&ddev->struct_mutex);
+	mutex_unlock(&ddev->filelist_mutex);
 }
 
 /*
@@ -769,7 +769,7 @@ static int amdgpu_debugfs_gem_info(struct seq_file *m, void *data)
 	struct drm_file *file;
 	int r;
 
-	r = mutex_lock_interruptible(&dev->struct_mutex);
+	r = mutex_lock_interruptible(&dev->filelist_mutex);
 	if (r)
 		return r;
 
@@ -793,7 +793,7 @@ static int amdgpu_debugfs_gem_info(struct seq_file *m, void *data)
 		spin_unlock(&file->table_lock);
 	}
 
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&dev->filelist_mutex);
 	return 0;
 }
 

drivers/gpu/drm/drm_drv.c

@@ -590,6 +590,7 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
 	spin_lock_init(&dev->buf_lock);
 	spin_lock_init(&dev->event_lock);
 	mutex_init(&dev->struct_mutex);
+	mutex_init(&dev->filelist_mutex);
 	mutex_init(&dev->ctxlist_mutex);
 	mutex_init(&dev->master_mutex);
 

drivers/gpu/drm/drm_fops.c

@@ -297,9 +297,9 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
 	}
 	mutex_unlock(&dev->master_mutex);
 
-	mutex_lock(&dev->struct_mutex);
+	mutex_lock(&dev->filelist_mutex);
 	list_add(&priv->lhead, &dev->filelist);
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&dev->filelist_mutex);
 
 #ifdef __alpha__
 	/*
@@ -447,8 +447,11 @@ int drm_release(struct inode *inode, struct file *filp)
 
 	DRM_DEBUG("open_count = %d\n", dev->open_count);
 
-	mutex_lock(&dev->struct_mutex);
+	mutex_lock(&dev->filelist_mutex);
 	list_del(&file_priv->lhead);
+	mutex_unlock(&dev->filelist_mutex);
+
+	mutex_lock(&dev->struct_mutex);
 	if (file_priv->magic)
 		idr_remove(&file_priv->master->magic_map, file_priv->magic);
 	mutex_unlock(&dev->struct_mutex);

drivers/gpu/drm/drm_info.c

@@ -174,7 +174,7 @@ int drm_clients_info(struct seq_file *m, void *data)
 	/* 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);
+	mutex_lock(&dev->filelist_mutex);
 	list_for_each_entry_reverse(priv, &dev->filelist, lhead) {
 		struct task_struct *task;
 
@@ -190,7 +190,7 @@ int drm_clients_info(struct seq_file *m, void *data)
 			   priv->magic);
 		rcu_read_unlock();
 	}
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&dev->filelist_mutex);
 	return 0;
 }
 

drivers/gpu/drm/i915/i915_debugfs.c

@@ -498,6 +498,10 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 
 	seq_putc(m, '\n');
 	print_batch_pool_stats(m, dev_priv);
+
+	mutex_unlock(&dev->struct_mutex);
+
+	mutex_lock(&dev->filelist_mutex);
 	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
 		struct file_stats stats;
 		struct task_struct *task;
@@ -518,8 +522,7 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 		print_file_stats(m, task ? task->comm : "<unknown>", stats);
 		rcu_read_unlock();
 	}
-
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&dev->filelist_mutex);
 
 	return 0;
 }
@@ -2325,6 +2328,7 @@ static int i915_ppgtt_info(struct seq_file *m, void *data)
 	else if (INTEL_INFO(dev)->gen >= 6)
 		gen6_ppgtt_info(m, dev);
 
+	mutex_lock(&dev->filelist_mutex);
 	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
 		struct drm_i915_file_private *file_priv = file->driver_priv;
 		struct task_struct *task;
@@ -2339,6 +2343,7 @@ static int i915_ppgtt_info(struct seq_file *m, void *data)
 		idr_for_each(&file_priv->context_idr, per_file_ctx,
 			     (void *)(unsigned long)m);
 	}
+	mutex_unlock(&dev->filelist_mutex);
 
 out_put:
 	intel_runtime_pm_put(dev_priv);
@@ -2374,6 +2379,8 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 		   intel_gpu_freq(dev_priv, dev_priv->rps.min_freq_softlimit),
 		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq_softlimit),
 		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq));
+
+	mutex_lock(&dev->filelist_mutex);
 	spin_lock(&dev_priv->rps.client_lock);
 	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
 		struct drm_i915_file_private *file_priv = file->driver_priv;
@@ -2396,6 +2403,7 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 		   list_empty(&dev_priv->rps.mmioflips.link) ? "" : ", active");
 	seq_printf(m, "Kernel boosts: %d\n", dev_priv->rps.boosts);
 	spin_unlock(&dev_priv->rps.client_lock);
+	mutex_unlock(&dev->filelist_mutex);
 
 	return 0;
 }

include/drm/drmP.h

@@ -769,6 +769,7 @@ struct drm_device {
 	atomic_t buf_alloc;		/**< Buffer allocation in progress */
 	/*@} */
 
+	struct mutex filelist_mutex;
 	struct list_head filelist;
 
 	/** \name Memory management */