Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

Ingo Molnar
2004-11-02T08:01:57Z

* Bill Huey <bhuey@lnxw.com> wrote:

> The lock chains aren't that deep in Linux so the algorithmic
> complexity is not going to hit some crazy polynomial time unless
> there's some seriously nasty contention at a certain point in the
> kernel (billions of readers for example against a write aquire). But
> when we start to see things like that under pressure is when we need
> to start shortening the need for that/those lock(s) for that/those
> critical section(s) in question.

also note that in the -U series i removed the true 'read' logic from
semaphores. What we have now are single writers only, plus readers
emulated as a writer plus the ability to self-recurse. ('writers' are
not allowed to self-recurse.) This is quite close to the semantic needs
of Linux rwlocks and rwsems and it simplified both locking, deadlock
detection and PI quite significantly.

Ingo