[Bug 214621] WARNING: CPU: 3 PID: 521 at drivers/gpu/drm/ttm/ttm_bo.c:409 ttm_bo_release+0xb64/0xe40 [ttm]

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=214621

--- Comment #10 from Lang Yu (Lang.Yu@amd.com) ---
(In reply to Christian König from comment #9)
> (In reply to Lang Yu from comment #8)
> > (In reply to Christian König from comment #7)
> > > Yeah, that won't work. As far as I can see the problem is not inside
> > amdgpu,
> > > but rather inside the driver which is importing buffers from amdgpu.
> > 
> > At least, we should call drm_prime_gem_destroy() to detach dma-buf(if
> > exists) before WARN_ON_ONCE(bo->pin_count).
> 
> Nope, that's incorrect. You are mixing things up here.
> 
> This is for the case when amdgpu imports a buffer, but the warning happens
> when amdgpu exports a buffer.
> 
> And on import you indeed only want to drop the attachment after the BO is
> really destroyed or not when the GEM handle is destroyed. Otherwise you
> could potentially unmap memory while it is still used by the hardware.
> 
> > And do you think if clients don't unmap/detach amdgpu dma-buf properly,
> > should amdgpu do that work? Thanks!
> 
> No. That rather looks like the importer is messing up some reference count
> and forgets to destroy the attachment before the dma-buf. There is
> absolutely nothing the exporter can do in that situation.
> 
> There is the slightly chance that the bug is indeed somewhere inside amdgpu
> or the dma-buf framework itself (Michel and I are huntin a similar issue at
> the moment), but it does work with other driver combinations.

Thanks for your clarification. Seems hard to reproduce the issue.

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are watching the assignee of the bug.