[BUG] gpu: drm: amdgpu: Possible sleep-in-atomic-context bugs in amdgpu_uvd_ring_begin_use()

[Jia-Ju Bai]

Sorry, I am still not clear why the call chain I proposed is incorrect...

I find a conditional in amdgpu_mm_wreg():

     if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev))
         return amdgpu_virt_kiq_wreg(adev, reg, v);

Is amdgpu_virt_kiq_wreg() never called from WREG32() or RREG32()?


Best wishes,
Jia-Ju Bai


On 2018/9/15 17:10, Koenig, Christian wrote:
> amdgpu_ring_alloc() does call amdgpu_uvd_begin_use(), but never in the 
> call chain you proposed.
>
> Thinking about it I actually don't see a way a statically analysis 
> could ever figure that out.
>
> Christian.
>
> Am 15.09.2018 11:05 schrieb Jia-Ju Bai <baijiaju1990 at gmail.com>:
>
>     Thanks for your reply.
>
>     On 2018/9/15 17:01, Koenig, Christian wrote:
>
>         Sorry to say that but your analysis tool is buggy.
>
>         The proposed call paths will never trigger.
>
>
>     Could you please explain which piece of the call path is incorrect?
>     I am not very sure of my function pointer analysis.
>     Does amdgpu_ring_alloc() never calls amdgpu_uvd_ring_begin_use()?
>
>     Thanks in advance.
>
>
>     Best wishes,
>     Jia-Ju Bai
>
>
>         Regards,
>         Christian.
>
>         Am 15.09.2018 10:59 schrieb Jia-Ju Bai
>         <baijiaju1990 at gmail.com> <mailto:baijiaju1990 at gmail.com>:
>         The driver may sleep with holding a spinlock.
>         The function call paths (from bottom to top) in Linux-4.17 are:
>
>         [FUNC] mutex_lock_nested
>         drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c, 1477:
>              mutex_lock_nested in amdgpu_dpm_enable_uvd
>         drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c, 1154:
>              amdgpu_dpm_enable_uvd in amdgpu_uvd_ring_begin_use
>         drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c, 80:
>              [FUNC_PTR]amdgpu_uvd_ring_begin_use in amdgpu_ring_alloc
>         drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c, 199:
>              amdgpu_ring_alloc in amdgpu_virt_kiq_wreg
>         drivers/gpu/drm/amd/amdgpu/amdgpu_device.c, 207:
>              amdgpu_virt_kiq_wreg in amdgpu_mm_wreg
>         drivers/gpu/drm/amd/amdgpu/vi.c, 207:
>              amdgpu_mm_wreg in vi_gc_cac_rreg
>         drivers/gpu/drm/amd/amdgpu/vi.c, 206:
>              _raw_spin_lock_irqsave in vi_gc_cac_rreg
>
>         [FUNC] mutex_lock_nested
>         drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c, 1477:
>              mutex_lock_nested in amdgpu_dpm_enable_uvd
>         drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c, 1154:
>              amdgpu_dpm_enable_uvd in amdgpu_uvd_ring_begin_use
>         drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c, 80:
>              [FUNC_PTR]amdgpu_uvd_ring_begin_use in amdgpu_ring_alloc
>         drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c, 199:
>              amdgpu_ring_alloc in amdgpu_virt_kiq_wreg
>         drivers/gpu/drm/amd/amdgpu/amdgpu_device.c, 207:
>              amdgpu_virt_kiq_wreg in amdgpu_mm_wreg
>         drivers/gpu/drm/amd/amdgpu/soc15.c, 106:
>              amdgpu_mm_wreg in soc15_pcie_rreg
>         drivers/gpu/drm/amd/amdgpu/soc15.c, 105:
>              _raw_spin_lock_irqsave in soc15_pcie_rreg
>
>         [FUNC] mutex_lock_nested
>         drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c, 1477:
>              mutex_lock_nested in amdgpu_dpm_enable_uvd
>         drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c, 1154:
>              amdgpu_dpm_enable_uvd in amdgpu_uvd_ring_begin_use
>         drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c, 80:
>              [FUNC_PTR]amdgpu_uvd_ring_begin_use in amdgpu_ring_alloc
>         drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c, 199:
>              amdgpu_ring_alloc in amdgpu_virt_kiq_wreg
>         drivers/gpu/drm/amd/amdgpu/amdgpu_device.c, 207:
>              amdgpu_virt_kiq_wreg in amdgpu_mm_wreg
>         drivers/gpu/drm/amd/amdgpu/cik.c, 139:
>              amdgpu_mm_wreg in cik_uvd_ctx_wreg
>         drivers/gpu/drm/amd/amdgpu/cik.c, 138:
>              _raw_spin_lock_irqsave in cik_uvd_ctx_wreg
>
>         [FUNC] mutex_lock_nested
>         drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c, 1477:
>              mutex_lock_nested in amdgpu_dpm_enable_uvd
>         drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c, 1154:
>              amdgpu_dpm_enable_uvd in amdgpu_uvd_ring_begin_use
>         drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c, 80:
>              [FUNC_PTR]amdgpu_uvd_ring_begin_use in amdgpu_ring_alloc
>         drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c, 199:
>              amdgpu_ring_alloc in amdgpu_virt_kiq_wreg
>         drivers/gpu/drm/amd/amdgpu/amdgpu_device.c, 207:
>              amdgpu_virt_kiq_wreg in amdgpu_mm_wreg
>         drivers/gpu/drm/amd/amdgpu/dce_v6_0.c, 126:
>              amdgpu_mm_wreg in dce_v6_0_audio_endpt_rreg
>         drivers/gpu/drm/amd/amdgpu/dce_v6_0.c, 125:
>              _raw_spin_lock_irqsave in dce_v6_0_audio_endpt_rreg
>
>         Note that [FUNC_PTR] means a function pointer call is used.
>
>         These bugs are found by my static analysis tool DSAC.
>
>
>         Best wishes,
>         Jia-Ju Bai
>
>
>

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