Re: [rtl] RTLinux & XFree 4.1

[David Olofson <david.olofson@reologica.se>]

On Monday 03 December 2001 17:31, Stefan Doehla wrote:
[...]
> Too much work meant:
> Are you a realtime programmer or a XFree programmer? (Personally: I
> wouldn't like to read some 1000 lines of code I don't understand ...)
> If you can fix the problem - do it ...

Well, for anyone with the time and motivation to hack XFree86;

	1. Some drivers don't bother to check the hardware
	   command FIFO status before writing, which occasionally
	   results in the CPU blocking on the PCI bus - which
	   really means *blocking* - even busmaster DMA is
	   delayed! In some cases, this can be fixed with a
	   configuration option, but I don't know if it fixes
	   the problem with all drivers, or all cases.

	2. Some drivers/servers disable IRQs directly using CPU
	   instructions (to implement fast sync constructs
	   without kernel calls?) - which means that no kernel
	   patch can prevent this from affecting RT IRQ latency!
	   Don't know if this is still the case with 4.1.x - and
	   no one knows for sure what's in those nVidia
	   drivers... ;-)


//David Olofson --- Programmer, Reologica Instruments AB

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