[PATCH 2/2] drm/dp/mst: take lock around looking up the branch device on hpd irq

[Dave Airlie]

From: Dave Airlie <airl...@redhat.com>

If we are doing an MST transaction and we've gotten HPD and we
lookup the device from the incoming msg, we should take the mgr
lock around it, so that mst_primary and mstb->ports are valid.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 3c7e5cd..15a6d8e 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1175,6 +1175,8 @@ static struct drm_dp_mst_branch 
*drm_dp_get_mst_branch_device(struct drm_dp_mst_
        struct drm_dp_mst_port *port;
        int i;
        /* find the port by iterating down */
+
+       mutex_lock(&mgr->lock);
        mstb = mgr->mst_primary;

        for (i = 0; i < lct - 1; i++) {
@@ -1194,6 +1196,7 @@ static struct drm_dp_mst_branch 
*drm_dp_get_mst_branch_device(struct drm_dp_mst_
                }
        }
        kref_get(&mstb->kref);
+       mutex_unlock(&mgr->lock);
        return mstb;
 }

-- 
2.4.1