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SubjectRe: [RFC] I still see people using cli()
From
Date
Victor Yodaiken <yodaiken@fsmlabs.com> writes:

> On Mon, Oct 08, 2001 at 07:59:05PM +0530, BALBIR SINGH wrote:
> > BTW, that brings me to another issue, once the kernel becomes preemptibel,
> what
>
> > are the locking issues? how are semaphores and spin-locks affected? Has
> anybody
>
> > defined or come up with the rules/document yet?
>
> IF the kernel becomes preemptible it will be so slow, so buggy, and so painful
> to maintain, that those issues won't matter.

The preemptible kernel work just takes the current SMP code, and
allows it to work on a single processor. You are not interruptted if
you have a lock held. This makes the number of cases in the kernel
simpler, and should improve maintenance as more people will be
affected by the SMP issues.

Right now there is a preemptible kernel patch being maintained
somewhere. I haven't had a chance to look recently. But the recent
threads on low latency mentioned it.

As for rules. They are the usual SMP rules. In earlier version there
was a requirement or that you used balanced constructs.

i.e.
spin_lock_irqsave
...
spin_unlock_irqrestore

and not.

spin_lock_irqsave
...
spin_unlock
..
restore_flags.


Eric
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