On Mon, Mar 09, 2020 at 12:15:29PM +0000, Chris Wilson wrote:
> Mark up the potential racy read in drm_mm_initialized(), as we want a
> cheap and cheerful check:
>
> [ 121.098731] BUG: KCSAN: data-race in _i915_gem_object_create_stolen [i915] / rm_hole
> [ 121.098766]
> [ 121.098789] write (marked) to 0xffff8881f01ed330 of 8 bytes by task 3568 on cpu 3:
> [ 121.098831] rm_hole+0x64/0x140
> [ 121.098860] drm_mm_insert_node_in_range+0x3d3/0x6c0
> [ 121.099254] i915_gem_stolen_insert_node_in_range+0x91/0xe0 [i915]
> [ 121.099646] _i915_gem_object_create_stolen+0x9d/0x100 [i915]
> [ 121.100047] i915_gem_object_create_region+0x7a/0xa0 [i915]
> [ 121.100451] i915_gem_object_create_stolen+0x33/0x50 [i915]
> [ 121.100849] intel_engine_create_ring+0x1af/0x280 [i915]
> [ 121.101242] __execlists_context_alloc+0xce/0x3d0 [i915]
> [ 121.101635] execlists_context_alloc+0x25/0x40 [i915]
> [ 121.102030] intel_context_alloc_state+0xb6/0xf0 [i915]
> [ 121.102420] __intel_context_do_pin+0x1ff/0x220 [i915]
> [ 121.102815] i915_gem_do_execbuffer+0x46b4/0x4c20 [i915]
> [ 121.103211] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915]
> [ 121.103244] drm_ioctl_kernel+0xe4/0x120
> [ 121.103269] drm_ioctl+0x297/0x4c7
> [ 121.103296] ksys_ioctl+0x89/0xb0
> [ 121.103321] __x64_sys_ioctl+0x42/0x60
> [ 121.103349] do_syscall_64+0x6e/0x2c0
> [ 121.103377] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 121.103403]
> [ 121.103426] read to 0xffff8881f01ed330 of 8 bytes by task 3109 on cpu 1:
> [ 121.103819] _i915_gem_object_create_stolen+0x30/0x100 [i915]
> [ 121.104228] i915_gem_object_create_region+0x7a/0xa0 [i915]
> [ 121.104631] i915_gem_object_create_stolen+0x33/0x50 [i915]
> [ 121.105025] intel_engine_create_ring+0x1af/0x280 [i915]
> [ 121.105420] __execlists_context_alloc+0xce/0x3d0 [i915]
> [ 121.105818] execlists_context_alloc+0x25/0x40 [i915]
> [ 121.106202] intel_context_alloc_state+0xb6/0xf0 [i915]
> [ 121.106595] __intel_context_do_pin+0x1ff/0x220 [i915]
> [ 121.106985] i915_gem_do_execbuffer+0x46b4/0x4c20 [i915]
> [ 121.107375] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915]
> [ 121.107409] drm_ioctl_kernel+0xe4/0x120
> [ 121.107437] drm_ioctl+0x297/0x4c7
> [ 121.107464] ksys_ioctl+0x89/0xb0
> [ 121.107489] __x64_sys_ioctl+0x42/0x60
> [ 121.107511] do_syscall_64+0x6e/0x2c0
> [ 121.107535] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
A bit on the fence on this, but also kinda the only option.
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> include/drm/drm_mm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
> index d7939c054259..ee8b0e80ca90 100644
> --- a/include/drm/drm_mm.h
> +++ b/include/drm/drm_mm.h
> @@ -272,7 +272,7 @@ static inline bool drm_mm_node_allocated(const struct drm_mm_node *node)
> */
> static inline bool drm_mm_initialized(const struct drm_mm *mm)
> {
> - return mm->hole_stack.next;
> + return READ_ONCE(mm->hole_stack.next);
> }
>
> /**
> --
> 2.20.1
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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