From: Daniel Vetter Date: Thu, 5 Jun 2014 09:12:03 +0000 (+0200) Subject: drm: Fix getconnector connection_mutex locking X-Git-Tag: firefly_0821_release~176^2~3773^2~11 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c7560f1281640b1232d1c3cb242aabf5bd83a857;p=firefly-linux-kernel-4.4.55.git drm: Fix getconnector connection_mutex locking I've fumbled my own idea and enthusiastically wrapped all the getconnector code with the connection_mutex. But we only need it to chase the connector->encoder link. Even there it's not really needed since races with userspace won't matter, but better paranoid and consistent about this stuff. If we grap it everywhere connector probe callbacks can't grab it themselves, which means they'll deadlock. i915 does that for the load detect pipe. Furthermore i915 needs to do a ww dance since we also need to grab the mutex of the load detect crtc. This is a regression from commit 6e9f798d91c526982cca0026cd451e8fdbf18aaf Author: Daniel Vetter Date: Thu May 29 23:54:47 2014 +0200 drm: Split connection_mutex out of mode_config.mutex (v3) Cc: Rob Clark Cc: Dave Airlie Cc: Ville Syrjälä Reported-by: Ville Syrjälä Signed-off-by: Daniel Vetter Reviewed-by: Rob Clark Signed-off-by: Dave Airlie --- diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index 43735f38cd17..239342f554b4 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -1838,7 +1838,6 @@ 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) { @@ -1872,10 +1871,12 @@ 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); if (connector->encoder) out_resp->encoder_id = connector->encoder->base.id; else out_resp->encoder_id = 0; + drm_modeset_unlock(&dev->mode_config.connection_mutex); /* * This ioctl is called twice, once to determine how much space is @@ -1937,7 +1938,6 @@ int drm_mode_getconnector(struct drm_device *dev, void *data, out_resp->count_encoders = encoders_count; out: - drm_modeset_unlock(&dev->mode_config.connection_mutex); mutex_unlock(&dev->mode_config.mutex); return ret;