drm: Fix deadlock due to getconnector locking changes

In commit ccfc08655d5fd5076828f45fb09194c070f2f63a
Author: Rob Clark <robdclark@gmail.com>
Date:   Thu Dec 18 16:01:48 2014 -0500

    drm: tweak getconnector locking

We need to extend the locking to cover connector->state reading for
atomic drivers, but the above commit was a bit too eager and also
included the fill_modes callback. Which on i915 on old platforms using
load detection needs to acquire modeset locks, resulting in a deadlock
on output probing.

Reported-by: Marc Finet <m.dreadlock@gmail.com>
Cc: Marc Finet <m.dreadlock@gmail.com>
Cc: robdclark@gmail.com
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 6b00173d1be4fd6c96f749a803dd23ab5495de88..6b6b07ff720ba612d3f3a82f1063d0432f28da1f 100644 (file)
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2127,7 +2127,6 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
        DRM_DEBUG_KMS("[CONNECTOR:%d:?]\n", out_resp->connector_id);
 
        mutex_lock(&dev->mode_config.mutex);
-       drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 
        connector = drm_connector_find(dev, out_resp->connector_id);
        if (!connector) {
@@ -2157,6 +2156,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
        out_resp->mm_height = connector->display_info.height_mm;
        out_resp->subpixel = connector->display_info.subpixel_order;
        out_resp->connection = connector->status;
+
+       drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
        encoder = drm_connector_get_encoder(connector);
        if (encoder)
                out_resp->encoder_id = encoder->base.id;