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[1045/1094] drm: Fix getconnector connection_mutex locking

Message ID 1413889294-31328-1046-git-send-email-dheerajx.s.jamwal@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Dheeraj Jamwal Oct. 21, 2014, 11 a.m. UTC 
From: Daniel Vetter <daniel.vetter@ffwll.ch>

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 <daniel.vetter@ffwll.ch>
Date:   Thu May 29 23:54:47 2014 +0200

    drm: Split connection_mutex out of mode_config.mutex (v3)

Cc: Rob Clark <robdclark@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 832fd395ce61710c82d871196f7c7cd41fb076b6)

Signed-off-by: Dheeraj Jamwal <dheerajx.s.jamwal@intel.com>
---
 drivers/gpu/drm/drm_crtc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 7b046ba..d4c94de 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;