SKL igt@prime_vgem@basic-userptr - WARNING: possible circular locking dependency detected

https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_9299/shard-skl5/igt@prime_vgem@basic-userptr.html Dmesg <6> [384.732710] Console: switching to colour dummy device 80x25 <6> [384.733324] [IGT] prime_vgem: executing <6> [384.876685] [IGT] prime_vgem: starting subtest basic-userptr <4> [385.026531] <4> [385.026566] ====================================================== <4> [385.026609] WARNING: possible circular locking dependency detected <4> [385.026656] 5.10.0-rc3-CI-CI_DRM_9299+ #1 (moved) Tainted: G U <4> [385.026702] ------------------------------------------------------ <4> [385.026746] prime_vgem/16542 is trying to acquire lock: <4> [385.026788] ffffffff82731ef0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x27/0x210 <4> [385.026888] but task is already holding lock: <4> [385.026933] ffffffff827539c0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: unmap_vmas+0x0/0x130 <4> [385.027042] which lock already depends on the new lock.