Re: [RFC] New locking primitive for 2.5

yodaiken
2002-02-07T19:56:44Z

On Thu, Feb 07, 2002 at 04:38:57PM +0100, Martin Wirth wrote:
> This is a request for comment on a new locking primitive
> called a combilock.
>
> The goal of this development is:
>
> 1. To allow for a better SMP scalability of semaphores used as Mutex
> 2. As a replacement for long held spinlocks in an preemptible kernel
>
> The new lock uses a combination of a spinlock and a (mutex-)semaphore.
> You can lock it for short-term issues in a spin-lock mode:
>
> combi_spin_lock(struct combilock *x)
> combi_spin_unlock(struct combilock *x)
>
> and for longer lasting tasks in a sleeping mode by:
>
> combi_mutex_lock(struct combilock *x)
> combi_mutex_unlock(struct combilock *x)
>
> If a spin_lock request is blocked by a mutex_lock call, the spin_lock
> attempt also sleeps i.e. behaves like a semaphore.

So what's the difference between combi_spin and combi_mutex?
combi_spin becomes
if not mutex locked, spin
else sleep
Bizzare

The entire concept is revolting.