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SubjectRe: Possible critical VIA vt82c686a chip bug (private question)
On Thu, Oct 26, 2000 at 12:04:21PM -0400, Richard B. Johnson wrote:

> ../drivers/block/ide.c, line 162, on version 2.2.17 does bad things
> to the timer. It writes 0 to the control-word for timer 0. This
> does the following:
>
> o Selects timer 0.
> o Latches the timer.
> o Selects mode 0.
> o Programs it to a 16 bit counter.
>
> The result is a latched (stopped) counter. Bits 5 and 4 should have been
> selected. Then you read bits 0-7 from 0x40, followed by bits 8-15 from
> the same port.
>
> Also, there is no spin-lock protecting access to these ports. If anybody
> else is mucking with the timer, all bets are off.

Well, at least on 2.4.0-test9, the above timing code is #ifed to
DISK_RECOVERY_TIME > 0, which in turn is #defined to 0 in
include/linux/ide.h.

So this is not our problem here. Anyway I guess it's time to hunt for
i8259 accesses in the kernel that lack the necessary spinlock, even when
they're not probably the cause of the problem we see here.

--
Vojtech Pavlik
SuSE Labs
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