drm/dp/mst: make sure mst_primary mstb is valid in work function

This validates the mst_primary under the lock, and then calls
into the check and send function. This makes the code a lot
easier to understand the locking rules in.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 132581c..1c96706 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1189,7 +1189,7 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m
                                               struct drm_dp_mst_branch *mstb)
 {
        struct drm_dp_mst_port *port;
-
+       struct drm_dp_mst_branch *mstb_child;
        if (!mstb->link_address_sent) {
                drm_dp_send_link_address(mgr, mstb);
                mstb->link_address_sent = true;
@@ -1204,17 +1204,31 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m
                if (!port->available_pbn)
                        drm_dp_send_enum_path_resources(mgr, mstb, port);
 
-               if (port->mstb)
-                       drm_dp_check_and_send_link_address(mgr, port->mstb);
+               if (port->mstb) {
+                       mstb_child = drm_dp_get_validated_mstb_ref(mgr, port->mstb);
+                       if (mstb_child) {
+                               drm_dp_check_and_send_link_address(mgr, mstb_child);
+                               drm_dp_put_mst_branch_device(mstb_child);
+                       }
+               }
        }
 }
 
 static void drm_dp_mst_link_probe_work(struct work_struct *work)
 {
        struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work);
+       struct drm_dp_mst_branch *mstb;
 
-       drm_dp_check_and_send_link_address(mgr, mgr->mst_primary);
-
+       mutex_lock(&mgr->lock);
+       mstb = mgr->mst_primary;
+       if (mstb) {
+               kref_get(&mstb->kref);
+       }
+       mutex_unlock(&mgr->lock);
+       if (mstb) {
+               drm_dp_check_and_send_link_address(mgr, mstb);
+               drm_dp_put_mst_branch_device(mstb);
+       }
 }
 
 static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,