drm/i915: Use a dummy timeline name for a signaled fence
authorChris Wilson <chris@chris-wilson.co.uk>
Thu, 30 Mar 2017 11:16:14 +0000 (12:16 +0100)
committerChris Wilson <chris@chris-wilson.co.uk>
Thu, 30 Mar 2017 13:18:38 +0000 (14:18 +0100)
commit05506b5be081b728353f1612b05c8ff689772832
treecfc08066a0e03c5ac2af7fa9b327e296b6b78b12
parenta69035ebdf385e1f69d824937f3104801b7fa8fb
drm/i915: Use a dummy timeline name for a signaled fence

Michał Winiarski pointed out that the debugging infrastructure (such as
trace_dma_fence_release) likes to pretty print the timeline name, long
after we have freed the timeline. Our timelines currently live as part of
the GTT (due to the strict ordering we currently use through each) which
belong to the context. We aim to free the context and release its
hardware resources as soon as we able to (i.e. when the last
fence/request using it has been signaled and retired). As the
.get_timeline_name is purely a debug feature, rather than extending the
lifetime of the context, or splitting it into many different release
phases just to keep the name around, replace the timeline name with a
constant after the fence has been signaled. This avoids the potential
use-after-free.

Reported-by: Krzysztof Olinski <krzysztof.e.olinski@intel.com>
Fixes: 80b204bce8f2 ("drm/i915: Enable multiple timelines")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <stable@vger.kernel.org> # v4.10+
Link: http://patchwork.freedesktop.org/patch/msgid/20170330111614.29757-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
drivers/gpu/drm/i915/i915_gem_request.c