On pe, 2016-08-12 at 18:52 +0100, Chris Wilson wrote: > Daniel Vetter proposed a new challenge to the serialisation inside the > busy-ioctl that exposed a flaw that could result in us reporting the > wrong engine as being busy. If the request is reallocated as we test > its busyness and then reassigned to this object by another thread, we > would not notice that the test itself was incorrect. > > We are faced with a choice of using __i915_gem_active_get_request_rcu() > to first acquire a reference to the request preventing the race, or to > acknowledge the race and accept the limitations upon the accuracy of the > busy flags. Note that we guarantee that we never falsely report the > object as idle (providing userspace itself doesn't race), and so the > most important use of the busy-ioctl and its guarantees are fulfilled. > If Daniel acks the userspace change, Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Regards, Joonas -- Joonas Lahtinen Open Source Technology Center Intel Corporation _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
