Re: furwocks: Fast Userspace Read/Write Locks

[Rusty Russell <rusty@rustcorp.com.au>]

In message <20020307153228.3A6773FE06@smtp.linux.ibm.com> you write:
> On Thursday 07 March 2002 07:50 am, Arjan van de Ven wrote:
> > Rusty Russell wrote:
> > > This is a userspace implementation of rwlocks on top of futexes.
> >
> > question: if rwlocks aren't actually slower in the fast path than
> > futexes,
> > would it make sense to only do the rw variant and in some userspace
> > layer
> > map "traditional" semaphores to write locks ?
> > Saves half the implementation and testing....
> 
> I m not in favor of that. The dominant lock will be mutexes.

To clarify: I'd love this, but rwlocks in the kernel aren't even
vaguely fair.  With a steady stream of overlapping readers, a writer
will never get the lock.

Hope that clarifies,
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.