Daniel noticed a problem where is we wrote to an object with ring A in the middle of a very long running batch, then executed a quick batch on ring B before a batch that reads from the same object, its obj->ring would now point to ring B, but its last_write_seqno would be still relative to ring A. This would allow for the user to read from the object before the GPU had completed the write, as set_domain would only check that ring B had passed the last_write_seqno.
To fix this simply (and inelegantly), we bump the last_write_seqno when switching rings so that the last_write_seqno is always relative to the current obj->ring. Signed-off-by: Chris Wilson <[email protected]> Cc: Daniel Vetter <[email protected]> Cc: [email protected] --- drivers/gpu/drm/i915/i915_gem.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 774620d..7c59cb1 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1954,6 +1954,10 @@ i915_gem_object_move_to_active(struct drm_i915_gem_object *obj, u32 seqno = intel_ring_get_seqno(ring); BUG_ON(ring == NULL); + if (obj->ring != ring && obj->last_write_seqno) { + /* Keep the seqno relative to the current ring */ + obj->last_write_seqno = seqno; + } obj->ring = ring; /* Add a reference if we're newly entering the active list. */ -- 1.8.3.2 _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
