Re: 2.1.111: IDE DMA disabled?

Alan Cox (
Wed, 29 Jul 1998 11:36:00 +0100 (BST)

> So by just reading the IDE status register you'd essentally guarantee that
> whatever DMA activity happened earlier will have completed as far as the
> CPU is concerned.

There are other implicit data races in any X86 code. I spent a fair chunk
of my early 1.3.3x SMP work staring at strange output because of it. Notably
the dirty bit on pages is updated by the hardware and no lock in the kernel
will stop that occuring if we have ordering wrong anywhere. Dave was never
totally convinced I even got 2.0 right


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