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.. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
