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SubjectRe: [patch] recover lost ticks
On Mon, Mar 15, 1999 at 01:28:27PM +0100, Ingo Molnar wrote:
> > I am not fixing the symptom, I am recovering the bug at runtime kprinting
> > the useful information as in your patch but with the difference that then
> > I am allowing the machine to run fine until the problem will get fixed
> > (and to get it fixed you may need to wait some time like in the scsi
> > code).
>
> the SCSI case is pure paranoia and an unmaintained subsystem. Fixing (one
> of ) the effects of overlong cli() just delays the real fix. (why should
> we bother fixing them when system time runs just fine) Some other
> side-effects of overlong clis, apart from lost timer ticks: lost
> characters on the serial line, lost keyboard events. If someone doing
> strange things can live with these other effects, he sure can live with
> lost timer ticks as well.

Well, almost any SCSI driver does things like
for (msec=1000; msec--; ) udelay (1000);
after a bus RESET was issued or detected. And the IRQ-safe io_request
spinlock is held.

I am not happy with this, and posted something to l-scsi, but nobody was
proposing a good solution other than major SCSI code rework in 2.3.

Maybe you can come up with a nice proposal.
Since then, I prefer Arca's patch which does both detect the problem and
still tries to the user from trouble.

Regards,
--
Dipl.Phys. Kurt Garloff <kurt@garloff.de> [Dortmund, FRG]
Plasma physics, high perf. computing [Linux-ix86,-axp, DUX]
PGP key: see mailheader / key servers [Linux SCSI driver: DC390]
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