From cd961bb9eebb630452f49dcbf3e5f0059428614a Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Wed, 28 Jan 2015 10:02:23 +0100 Subject: drm/mst: fix recursive sleep warning on qlock With drm-next, we can get a backtrace from sleeping with mutex detection. this is due to the callback checking the txmsg state taking the mutex, which can cause a sleep inside a sleep, Daniel went over it and was happy we could drop this mutex in this case. Signed-off-by: Dave Airlie --- drivers/gpu/drm/drm_dp_mst_topology.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'drivers/gpu/drm/drm_dp_mst_topology.c') diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 9a5b68717ec8..379ab4555756 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -733,10 +733,14 @@ static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { bool ret; - mutex_lock(&mgr->qlock); + + /* + * All updates to txmsg->state are protected by mgr->qlock, and the two + * cases we check here are terminal states. For those the barriers + * provided by the wake_up/wait_event pair are enough. + */ ret = (txmsg->state == DRM_DP_SIDEBAND_TX_RX || txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT); - mutex_unlock(&mgr->qlock); return ret; } @@ -1363,12 +1367,13 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, return 0; } -/* must be called holding qlock */ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; int ret; + WARN_ON(!mutex_is_locked(&mgr->qlock)); + /* construct a chunk from the first msg in the tx_msg queue */ if (list_empty(&mgr->tx_msg_downq)) { mgr->tx_down_in_progress = false; -- cgit