I haven't gone to see where it started, but as of late a good number of pretty nasty deadlock issues have appeared with the kernel. Easy reproduction recipe on a laptop with i915/amdgpu prime with lockdep enabled:
DRI_PRIME=1 glxinfo
Additionally, some more race conditions exist that I've managed to trigger with piglit and lockdep enabled after applying these patches:
============================= WARNING: suspicious RCU usage 4.14.3Lyude-Test+ #2 Not tainted ----------------------------- ./include/linux/reservation.h:216 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1 1 lock held by ext_image_dma_b/27451: #0: (reservation_ww_class_mutex){+.+.}, at: [<ffffffffa034f2ff>] ttm_bo_unref+0x9f/0x3c0 [ttm]
stack backtrace: CPU: 0 PID: 27451 Comm: ext_image_dma_b Not tainted 4.14.3Lyude-Test+ #2 Hardware name: HP HP ZBook 15 G4/8275, BIOS P70 Ver. 01.02 06/09/2017 Call Trace: dump_stack+0x8e/0xce lockdep_rcu_suspicious+0xc5/0x100 reservation_object_copy_fences+0x292/0x2b0 ? ttm_bo_unref+0x9f/0x3c0 [ttm] ttm_bo_unref+0xbd/0x3c0 [ttm] amdgpu_bo_unref+0x2a/0x50 [amdgpu] amdgpu_gem_object_free+0x4b/0x50 [amdgpu] drm_gem_object_free+0x1f/0x40 [drm] drm_gem_object_put_unlocked+0x40/0xb0 [drm] drm_gem_object_handle_put_unlocked+0x6c/0xb0 [drm] drm_gem_object_release_handle+0x51/0x90 [drm] drm_gem_handle_delete+0x5e/0x90 [drm] ? drm_gem_handle_create+0x40/0x40 [drm] drm_gem_close_ioctl+0x20/0x30 [drm] drm_ioctl_kernel+0x5d/0xb0 [drm] drm_ioctl+0x2f7/0x3b0 [drm] ? drm_gem_handle_create+0x40/0x40 [drm] ? trace_hardirqs_on_caller+0xf4/0x190 ? trace_hardirqs_on+0xd/0x10 amdgpu_drm_ioctl+0x4f/0x90 [amdgpu] do_vfs_ioctl+0x93/0x670 ? __fget+0x108/0x1f0 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x23/0xc2
I've also added the relevant fixes for the issue mentioned above.
Christian König (3): drm/ttm: fix ttm_bo_cleanup_refs_or_queue once more dma-buf: make reservation_object_copy_fences rcu save drm/amdgpu: reserve root PD while releasing it
Michel Dänzer (1): drm/ttm: Always and only destroy bo->ttm_resv in ttm_bo_release_list
drivers/dma-buf/reservation.c | 56 +++++++++++++++++++++++++--------- drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 13 ++++++-- drivers/gpu/drm/ttm/ttm_bo.c | 43 +++++++++++++------------- 3 files changed, 74 insertions(+), 38 deletions(-)
-- 2.14.3