Mailing List Archive

Alan Cox wrote:
>
> The only horrible case to watch is terminating a live DMA. PCI does write
> posting so doing
>
>
> writel(STOP_DMA, card->control);
> kfree(buf);
>
> is fatal every so often, as the write will be posted, the buffer freed,
> reallocated and trashed before the DMA is posted. Instead use
>
> writel(STOP_DMA, card->control);
> readl(card->anythingboring);
> kfree(buf);
In theory even this isn't safe, since the read return is allowed to pass
inbound DMAs according to the PCI spec. In practice I doubt any non-
buggy hardware would actually do this to you. (I've got some hardware
that does, and I certainly consider it to be buggy...)
--
............................................................................
Peter Desnoyers
162 Pleasant St. (617) 661-1979 pjd@fred.cambridge.ma.us
Cambridge, Mass. 02139 (978) 461-0402 (work) pjd@giga-net.com
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