Re: mm->mmap_sem

[James Simmons <jsimmons@edgeglobal.com>]

> No, you are trying to do _mandatory_ locking enforced by the kernel.
> For cooperative locking on sane GFX hardware a userspace spinlock is
> indeed all that is required, but for the broken hardware you are talking
> about kernel locking would be required.

What are all the broken cards out their? I was reading my old Matrox
Millenium I docs and even that card supports similutaneous access to 
the accel engine and framebuffer. If the number of cards that are that
broken are small then I just will not support them.

> This means that when the accel engine is initiated you must unmap all
> pages of the framebuffer (8k pages on modern cards), install a no-page
> handler and flush the TLBs of all processors.

All the processors!! Thats really bad.



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