[Intel-gfx] [RFC PATCH] drm/radeon: fixup locking inversion between mmap_sem and reservations

[Maarten Lankhorst]

op 08-10-13 16:33, Jerome Glisse schreef:
> On Tue, Oct 08, 2013 at 04:14:40PM +0200, Maarten Lankhorst wrote:
>> Allocate and copy all kernel memory before doing reservations. This prevents a locking
>> inversion between mmap_sem and reservation_class, and allows us to drop the trylocking
>> in ttm_bo_vm_fault without upsetting lockdep.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
> I would say NAK. Current code only allocate temporary page in AGP case.
> So AGP case is userspace -> temp page -> cs checker -> radeon ib.
>
> Non AGP is directly memcpy to radeon IB.
>
> Your patch allocate memory memcpy userspace to it and it will then be
> memcpy to IB. Which means you introduce an extra memcpy in the process
> not something we want.
>
Can we move up the call to radeon_ib_get then to be done before calling radeon_cs_parser_relocs?

~Maarten