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SubjectRe: [patch]2.4.0-test6 "spinlock" preemption patch
On Tue, 12 Sep 2000, Andrea Arcangeli wrote:
> On Wed, 6 Sep 2000, George Anzinger wrote:
>
> >The times a kernel is not preemptable under this patch are:
> >
> >While handling interrupts.
> >While doing "bottom half" processing.
> >While holding a spinlock, writelock or readlock.
> >
> >At all other times the algorithm allows preemption.
>
> So it can deadlock if somebody is doing:
>
> while (test_and_set_bit(0, &something)) {
> /* critical section */
> mb();
> clear_bit(0, &something);
> }

> The above construct it's discouraged of course when you can do
> the same thing with a spinlock but some place is doing that.

Hmmm, maybe the Montavista people can volunteer to clean
up all those places in the kernel code? ;)

cheers,

Rik
--
"What you're running that piece of shit Gnome?!?!"
-- Miguel de Icaza, UKUUG 2000

http://www.conectiva.com/ http://www.surriel.com/

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