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author | Dave Airlie <airlied@redhat.com> | 2015-06-15 10:34:28 +1000 |
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committer | Dave Airlie <airlied@redhat.com> | 2015-06-25 11:57:23 +1000 |
commit | 6b8eeca65b18ae77e175cc2b6571731f0ee413bf (patch) | |
tree | df8de7144582b43d6e90024dc1a88fc873906499 /drivers | |
parent | 8b72ce158cf0dba443e36fc66e0bb29c2580e0b6 (diff) | |
download | op-kernel-dev-6b8eeca65b18ae77e175cc2b6571731f0ee413bf.zip op-kernel-dev-6b8eeca65b18ae77e175cc2b6571731f0ee413bf.tar.gz |
drm/dp/mst: close deadlock in connector destruction.
I've only seen this once, and I failed to capture the
lockdep backtrace, but I did some investigations.
If we are calling into the MST layer from EDID probing,
we have the mode_config mutex held, if during that EDID
probing, the MST hub goes away, then we can get a deadlock
where the connector destruction function in the driver
tries to retake the mode config mutex.
This offloads connector destruction to a workqueue,
and avoid the subsequenct lock ordering issue.
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/gpu/drm/drm_dp_mst_topology.c | 40 |
1 files changed, 38 insertions, 2 deletions
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index f721349..778bbb6 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -867,8 +867,16 @@ static void drm_dp_destroy_port(struct kref *kref) port->vcpi.num_slots = 0; kfree(port->cached_edid); - if (port->connector) - (*port->mgr->cbs->destroy_connector)(mgr, port->connector); + + /* we can't destroy the connector here, as + we might be holding the mode_config.mutex + from an EDID retrieval */ + if (port->connector) { + mutex_lock(&mgr->destroy_connector_lock); + list_add(&port->connector->destroy_list, &mgr->destroy_connector_list); + mutex_unlock(&mgr->destroy_connector_lock); + schedule_work(&mgr->destroy_connector_work); + } drm_dp_port_teardown_pdt(port, port->pdt); if (!port->input && port->vcpi.vcpi > 0) @@ -2649,6 +2657,30 @@ static void drm_dp_tx_work(struct work_struct *work) mutex_unlock(&mgr->qlock); } +static void drm_dp_destroy_connector_work(struct work_struct *work) +{ + struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work); + struct drm_connector *connector; + + /* + * Not a regular list traverse as we have to drop the destroy + * connector lock before destroying the connector, to avoid AB->BA + * ordering between this lock and the config mutex. + */ + for (;;) { + mutex_lock(&mgr->destroy_connector_lock); + connector = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_connector, destroy_list); + if (!connector) { + mutex_unlock(&mgr->destroy_connector_lock); + break; + } + list_del(&connector->destroy_list); + mutex_unlock(&mgr->destroy_connector_lock); + + mgr->cbs->destroy_connector(mgr, connector); + } +} + /** * drm_dp_mst_topology_mgr_init - initialise a topology manager * @mgr: manager struct to initialise @@ -2668,10 +2700,13 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->lock); mutex_init(&mgr->qlock); mutex_init(&mgr->payload_lock); + mutex_init(&mgr->destroy_connector_lock); INIT_LIST_HEAD(&mgr->tx_msg_upq); INIT_LIST_HEAD(&mgr->tx_msg_downq); + INIT_LIST_HEAD(&mgr->destroy_connector_list); INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work); INIT_WORK(&mgr->tx_work, drm_dp_tx_work); + INIT_WORK(&mgr->destroy_connector_work, drm_dp_destroy_connector_work); init_waitqueue_head(&mgr->tx_waitq); mgr->dev = dev; mgr->aux = aux; @@ -2696,6 +2731,7 @@ EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init); */ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) { + flush_work(&mgr->destroy_connector_work); mutex_lock(&mgr->payload_lock); kfree(mgr->payloads); mgr->payloads = NULL; |