Re: CVS commit: src/sys

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Sat, Jul 30, 2011 at 10:16:30PM +0100, David Laight wrote:
> On Sat, Jul 30, 2011 at 11:04:24PM +0200, Joerg Sonnenberger wrote:
> ... 
> > Note that for a uncontested resource, the overhead of a mutex for a
> > single operation tends to be comparable, if store fences have a similar
> > price than bus locked operation on an owned cache line.
> 
> I remember being told that you couldn't avoid a lock, and algorithms
> that claimed to do so were broken.

You can avoid some properties of a lock. E.g. if you are using a
lock-free queue in shared memory, you can completely kill a process at
any point and the queue will still be in a consistent state.

Joerg