On Fri, Jun 19, 2015 at 10:53:10AM +1000, Dave Airlie wrote: > From: Dave Airlie <airlied@xxxxxxxxxx> > > We should validate the passed in mstb under the lock > this should stop us getting an invalid mstb here. > > (first attempt with cancelling work has lockdep issues). Yeah cancel_work_sync is nasty that way ;-) Btw random bikeshed, but mgr->work would look nice as mgr->probe_work. > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89366 Bugzilla: https://bugs.archlinux.org/task/45369 seems the more accurate one, the fdo one is a mess. > > Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx> > --- > drivers/gpu/drm/drm_dp_mst_topology.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c > index fb65f5d..ad0d1bf 100644 > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > @@ -1198,9 +1198,14 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_ > } > > static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr, > - struct drm_dp_mst_branch *mstb) > + struct drm_dp_mst_branch *mstb_in) > { > struct drm_dp_mst_port *port; > + struct drm_dp_mst_branch *mstb; > + > + mstb = drm_dp_get_validated_mstb_ref(mgr, mstb_in); > + if (!mstb) > + return; > > if (!mstb->link_address_sent) { > drm_dp_send_link_address(mgr, mstb); > @@ -1219,6 +1224,7 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m > if (port->mstb) > drm_dp_check_and_send_link_address(mgr, port->mstb); > } > + drm_dp_put_mst_branch_device(mstb); > } I am a bit concerned about the lifetime rules of the mgr->mst_primary pointer. port->mstb is controlled by the lifetime of the port and that by the parent mst branch, so I think we're covered dereferencing that one. But mgr->mst_primary seems to be protected only by mgr->lock, and you're not holding that in the probe work. I did review drm_dp_mst_topology_mgr_set_mst and that does seem to clean up ->mst_primary correctly but might be helped with a comment. But we do need the locking I think. Assuming the added locking doesn't piss off lockdep this is Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> -Daniel --- diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 132581ca4ad8..08c3c65e7d08 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1213,7 +1213,9 @@ static void drm_dp_mst_link_probe_work(struct work_struct *work) { struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work); + mutex_lock(&mgr->lock); drm_dp_check_and_send_link_address(mgr, mgr->mst_primary); + mutex_unlock(&mgr->lock); } @@ -1921,6 +1923,8 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms } else { /* disable MST on the device */ mstb = mgr->mst_primary; + /* inherit reference from ->mst_primary, will be cleaned up + * at the end. */ mgr->mst_primary = NULL; /* this can fail if the device is gone */ drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0); -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
