On 20 June 2015 at 01:42, Daniel Vetter <daniel@xxxxxxxx> wrote: > 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. yes probably. > 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. That won't work as we take the lock to do the lookups later, It doesn't actually matter if mgr->mst_primary gets messed up here I don't think, as long as we validate it. So the value is going to be either a) correct, b) NULL, c) garbage between a and b assuming its not atomic, the validate function locks the mgr, and checks primary, at this point primary will either be a or b as we hold the lock, and if primary from outside the function is a, b or c won't matter as the validation will either pass or fail depending on the state under the lock. Though in reviewing that I did find another bug with primary which I'll send another fix for. Dave. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
