From 992d38cc787d353aba8b0e13d37a719a3431db79 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sat, 13 May 2017 11:52:00 +0100 Subject: [PATCH] drm/dp: Read the tx msg state once after checking for an event Both as an exercise to document that we are reading the state outside of the appropriate mutex and to ensure that we only read the value once before the multiple comparisons, use READ_ONCE. Signed-off-by: Chris Wilson Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20170513105201.17658-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d1cbb9c8f806..3bdd314f02b1 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -737,16 +737,16 @@ static void drm_dp_mst_put_payload_id(struct drm_dp_mst_topology_mgr *mgr, static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { - bool ret; + unsigned int state; /* * 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); - return ret; + state = READ_ONCE(txmsg->state); + return (state == DRM_DP_SIDEBAND_TX_RX || + state == DRM_DP_SIDEBAND_TX_TIMEOUT); } static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, -- 2.20.1