Re: 2.6.4 on Alpha uninterruptible sleep of processes

From: Marc Giger
Date: Sat Mar 13 2004 - 05:12:35 EST

Hi Ivan,

On Sat, 13 Mar 2004 02:01:41 +0300
Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Fri, Mar 12, 2004 at 09:52:15PM +0100, Marc Giger wrote:
> > Right now I'm recompiling the kernel. So you say this patch isn't a
> > fix but a test?
> Yes. That patch just reverts new alpha semaphore stuff which went
> into 2.6.4.
> > This time I have additionally "semaphore debugging" enabled,
> > perhaps it's useful for you.
> Thanks, this might be helpful.

Hmm, I couldn't boot the kernel with enabled "semaphore debugging". It
hangs directly after aboot. No messages, nothing. Do I something wrong?
Now I've booted 2.6.4 without debugging.

> > > The answer is here:
> > >
> >
> > That's no answer, that's a statement:-) Do know the exactly reason
> > why it should be a bad idea? Is it mostly a bad idea on alpha?
> Hmm, I haven't discussed that with Richard, so I can't speak for him
> :-) IMHO, the benefits of the kernel preempt support in general are
> more than doubtful, the level of complexity that it adds to the kernel
> code is just unacceptable.

Ok, but I read somewhere exactly the opposite (lkml?).
The statement was something like the following: "Preempt doesn't need
much more infrastrucure in kernel code, because the needed locking
mechanism is already there (SMP)."

So I'm confused now:-) But I understand that every little more
complexity is not for free. More task switches etc...

Thank you for the infos.


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