i915_gem_handle_seqno_wrap() will zero all sync_seqnos but as the wrap can happen inside ring->sync_to(), pre wrap seqno was carried over and overwrote the zeroed sync_seqno. When wrap is handled, all outstanding requests will be retired and objects moved to inactive queue, causing their last_read_seqno to be zero. Use this to update the sync_seqno correctly. RING_SYNC registers after wrap will contain pre wrap values which are >= seqno. So injecting the semaphore wait into ring completes immediately. Original idea for using last_read_seqno from Chris Wilson. Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk> --- drivers/gpu/drm/i915/i915_gem.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 85a0948..4ef8b57 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2397,7 +2397,11 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj, ret = to->sync_to(to, from, seqno); if (!ret) - from->sync_seqno[idx] = seqno; + /* We use last_read_seqno because sync_to() + * might have just caused seqno wrap under + * the radar. + */ + from->sync_seqno[idx] = obj->last_read_seqno; return ret; } -- 1.7.9.5
