drm/msm: Fix debugfs deadlock

In normal cases the gem obj lock is acquired first before mm_lock.  The
exception is iterating the various object lists.  In the shrinker path,
deadlock is avoided by using msm_gem_trylock() and skipping over objects
that cannot be locked.  But for debugfs the straightforward thing is to
split things out into a separate list of all objects protected by it's
own lock.

Fixes: d984457b31c4 ("drm/msm: Add priv->mm_lock to protect active/inactive lists")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210401012722.527712-4-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

diff --git a/drivers/gpu/drm/msm/msm_debugfs.c b/drivers/gpu/drm/msm/msm_debugfs.c
index 85ad0ba..d611cc8 100644 (file)
--- a/drivers/gpu/drm/msm/msm_debugfs.c
+++ b/drivers/gpu/drm/msm/msm_debugfs.c
@@ -111,23 +111,15 @@ static const struct file_operations msm_gpu_fops = {
 static int msm_gem_show(struct drm_device *dev, struct seq_file *m)
 {
        struct msm_drm_private *priv = dev->dev_private;
-       struct msm_gpu *gpu = priv->gpu;
        int ret;
 
-       ret = mutex_lock_interruptible(&priv->mm_lock);
+       ret = mutex_lock_interruptible(&priv->obj_lock);
        if (ret)
                return ret;
 
-       if (gpu) {
-               seq_printf(m, "Active Objects (%s):\n", gpu->name);
-               msm_gem_describe_objects(&gpu->active_list, m);
-       }
-
-       seq_printf(m, "Inactive Objects:\n");
-       msm_gem_describe_objects(&priv->inactive_dontneed, m);
-       msm_gem_describe_objects(&priv->inactive_willneed, m);
+       msm_gem_describe_objects(&priv->objects, m);
 
-       mutex_unlock(&priv->mm_lock);
+       mutex_unlock(&priv->obj_lock);
 
        return 0;
 }

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index c4e01b5..e12d5fb 100644 (file)
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -446,6 +446,9 @@ static int msm_drm_init(struct device *dev, const struct drm_driver *drv)
 
        priv->wq = alloc_ordered_workqueue("msm", 0);
 
+       INIT_LIST_HEAD(&priv->objects);
+       mutex_init(&priv->obj_lock);
+
        INIT_LIST_HEAD(&priv->inactive_willneed);
        INIT_LIST_HEAD(&priv->inactive_dontneed);
        INIT_LIST_HEAD(&priv->inactive_purged);

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 5cad921..2536340 100644 (file)
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -174,7 +174,14 @@ struct msm_drm_private {
        struct msm_rd_state *hangrd;   /* debugfs to dump hanging submits */
        struct msm_perf_state *perf;
 
-       /*
+       /**
+        * List of all GEM objects (mainly for debugfs, protected by obj_lock
+        * (acquire before per GEM object lock)
+        */
+       struct list_head objects;
+       struct mutex obj_lock;
+
+       /**
         * Lists of inactive GEM objects.  Every bo is either in one of the
         * inactive lists (depending on whether or not it is shrinkable) or
         * gpu->active_list (for the gpu it is active on[1])

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 156e4ec..b8dde53 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -961,7 +961,7 @@ void msm_gem_describe_objects(struct list_head *list, struct seq_file *m)
        size_t size = 0;
 
        seq_puts(m, "   flags       id ref  offset   kaddr            size     madv      name\n");
-       list_for_each_entry(msm_obj, list, mm_list) {
+       list_for_each_entry(msm_obj, list, node) {
                struct drm_gem_object *obj = &msm_obj->base;
                seq_puts(m, "   ");
                msm_gem_describe(obj, m);
@@ -980,6 +980,10 @@ void msm_gem_free_object(struct drm_gem_object *obj)
        struct drm_device *dev = obj->dev;
        struct msm_drm_private *priv = dev->dev_private;
 
+       mutex_lock(&priv->obj_lock);
+       list_del(&msm_obj->node);
+       mutex_unlock(&priv->obj_lock);
+
        mutex_lock(&priv->mm_lock);
        if (msm_obj->dontneed)
                mark_unpurgable(msm_obj);
@@ -1169,6 +1173,10 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
        list_add_tail(&msm_obj->mm_list, &priv->inactive_willneed);
        mutex_unlock(&priv->mm_lock);
 
+       mutex_lock(&priv->obj_lock);
+       list_add_tail(&msm_obj->node, &priv->objects);
+       mutex_unlock(&priv->obj_lock);
+
        return obj;
 
 fail:
@@ -1239,6 +1247,10 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,
        list_add_tail(&msm_obj->mm_list, &priv->inactive_willneed);
        mutex_unlock(&priv->mm_lock);
 
+       mutex_lock(&priv->obj_lock);
+       list_add_tail(&msm_obj->node, &priv->objects);
+       mutex_unlock(&priv->obj_lock);
+
        return obj;
 
 fail:

diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 13aabfe..e6b28ed 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -60,10 +60,16 @@ struct msm_gem_object {
         */
        uint8_t vmap_count;
 
+       /**
+        * Node in list of all objects (mainly for debugfs, protected by
+        * priv->obj_lock
+        */
+       struct list_head node;
+
        /**
         * An object is either:
-        *  inactive - on priv->inactive_dontneed/willneed/purged depending
-        *     on status
+        *  inactive - on priv->inactive_dontneed or priv->inactive_willneed
+        *     (depending on purgability status)
         *  active   - on one one of the gpu's active_list..  well, at
         *     least for now we don't have (I don't think) hw sync between
         *     2d and 3d one devices which have both, meaning we need to