Re: [RFC] Cancellable MCS spinlock rework

[Jason Low]

On Thu, 2014-07-03 at 08:35 -0700, Linus Torvalds wrote:
> On Thu, Jul 3, 2014 at 8:31 AM, Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > I don't think we'll support 2 _billion_ processes/threads waiting on
> > the same semaphore any time soon, so the 'long' seems a bit of an
> > overkill on 64-bit architectures.
> 
> Oh, never mind. The 'struct semaphore' uses it as just a plain count,
> but the rwsem ends up splitting up the bits for readers/writers, so we
> actually do want the full 64-bit value there.

Yeah, that was the key to reducing the struct size as the rwsem count
can't share a 64 bit chunk with the spinlock, unlike some of the other
lock.

Thanks,
Jason

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/