Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : Peter Dimov
Date : Wed May 25 2005 04:23 pm

David Schwartz wrote:
> "doug" <noone@nowhere.co.uk> wrote in message
> news:ZyPje.1900$iq5.1180@fe1.news.blueyonder.co.uk...
>
>> I know where you're coming from - that's where I came from too.  But
>> some folk (Peter, Giancarlo) explained that *yes*, you might read
>> the wrong value, but it doesn't matter.  You're guaranteed to get
>> the answer to the question "do I own this lock" correct.
>
>    Guaranteed by what?
>
>    Suppose you are thread "A1". The lock is held by "A2" and
> transfers to "B1" while you are checking the owner field. What stops
> you from seeing half of each and getting "A1", and thinking you own
> the lock?

We've been assuming atomic reads and writes, just no msync.

.