Re: 2.6.4 on Alpha uninterruptible sleep of processes

[Marc Giger <gigerstyle@gmx.ch>]

Hi Ivan,

On Sat, 13 Mar 2004 02:01:41 +0300
Ivan Kokshaysky <ink@jurassic.park.msu.ru> 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:
> > > http://bugzilla.kernel.org/show_bug.cgi?id=397
> > 
> > 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.

greets

Marc