Re: SMP and mmap

Alan Cox (alan@lxorguk.ukuu.org.uk)
Sat, 18 Sep 1999 19:11:13 +0100 (BST)

> framebuffer at the same time as the accel engine. Well one solution was to
> unmap the framebuffer just before someone would access the accel engine.
> Then use a no_page routine to put processes to sleep while the accel
> engine was active. Then once the accel engine was idle wake up all the
> processes that attempted framebuffer access. Now this soultion is far to
> expensive. So I have been looking for another way.

That is expensive. It also requires you create a synchronization point at
PCI level

> try to access the MMIO mmap accel regions. This would confuse most
> cards. How could I prevent this from happening?

Ok if user space has fb mmapped the user is runnign X11 or a graphical
full screen app 99.99999% of the time. So why not simply ignore the problem.
When a user mmaps the fb finish any pending accelerations and stop using
acceleration in the driver until they unmap

Alan

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