Op 29-06-17 om 11:44 schreef Daniel Vetter: > On Thu, Jun 29, 2017 at 11:33 AM, Maarten Lankhorst > <maarten.lankhorst@xxxxxxxxxxxxxxx> wrote: >> Op 29-06-17 om 11:23 schreef Daniel Vetter: >>> On Thu, Jun 29, 2017 at 11:10 AM, Maarten Lankhorst >>> <maarten.lankhorst@xxxxxxxxxxxxxxx> wrote: >>>> Op 27-06-17 om 16:59 schreef Daniel Vetter: >>>>> From: Thierry Reding <treding@xxxxxxxxxx> >>>>> >>>>> Move the modeset locking from drivers into FB helpers. >>>>> >>>>> v2: Also handle intel_connector_add_to_fbdev. >>>>> >>>>> Tested-by: John Stultz <john.stultz@xxxxxxxxxx> >>>>> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> (v1) >>>>> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> >>>>> --- >>>>> drivers/gpu/drm/drm_fb_helper.c | 40 +++++++++++++++++++++++++++++----- >>>>> drivers/gpu/drm/i915/intel_dp_mst.c | 6 ----- >>>>> drivers/gpu/drm/radeon/radeon_dp_mst.c | 7 ------ >>>>> 3 files changed, 34 insertions(+), 19 deletions(-) >>>> I know we suck at DP-MST. But I fear the unregister leaves open a race with mst_port being unset without connection_mutex.. >>>> >>>> best_encoder() and mode_valid() appear to use it. It's probably harmless and I have no good solution, so maybe just annotate it in the patch? Might also affect i915_hpd_poll_init_work, though I think the race in itself is harmless. >>> Hm, but this did race even before that already ... Should I just wrap >>> the mst_port = NULL in the connection_mutex? With a big warning that >>> we should have proper refcounting for this instead (both connectors >>> and all the mst things are refcounted already). >>> -Daniel >> I think leave open the race, the DP-MST modeset code itself doesn't use the connector->mst_port, just the detect callbacks do. In case of nonblocking modeset mst_port might already fall away so it's not like the race is any worse now. >> >> I don't even know how to solve it, except by not unplugging. :) > Why does grabbing the lock not fix the race? ->detect eventually calls > drm_dp_get_validated_port_ref, which will bail on a zombie mst port.. Oh ok. But there will always be a race. If DP-MST fails immediately after drm_dp_get_validated_port_ref, you'd still not be able to do anything about it. :) _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
