[PATCH 0/4] Backported amdgpu ttm deadlock fixes for 4.14

Lyude Paul lyude at redhat.com
Fri Dec 1 00:23:02 UTC 2017

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:
     ? 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]
     ? __fget+0x108/0x1f0

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(-)


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