drm/i915: Serialise read/write of the barrier's engine

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We use the request pointer inside the i915_active_node as the indicator
of the barrier's status; we mark it as used during
i915_request_add_active_barriers(), and search for an available barrier
in reuse_idle_barrier(). That check must be carefully serialised to
ensure we do use an engine for the barrier and not just a random
pointer. (Along the other reuse path, we are fully serialised by the
timeline->mutex.) The acquisition of the barrier itself is ordered through
the strong memory barrier in llist_del_all().

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111397
Fixes: d8af05ff38 ("drm/i915: Allow sharing the idle-barrier from other kernel requests")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190813200905.11369-1-chris@chris-wilson.co.uk

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Chris Wilson 2019-08-13 21:09:05 +01:00

parent b26496ae78

commit f130b712ff

1 changed files with 23 additions and 5 deletions

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drivers/gpu/drm/i915/i915_active.c

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