Subj : Re: double-checked locking in C
To   : comp.programming.threads
From : David Schwartz
Date : Thu Jul 07 2005 05:27 pm


"Chris Friesen" <cfriesen@nortel.com> wrote in message 
news:11craebqk6u9v93@corp.supernews.com...

> Consider a hypothetical cpu that does everything it can to screw up 
> programs which are not written to the POSIX standard:  It's a multi-cpu 
> box with no cache coherence.  Data is modified in local cache, and random 
> bits of it get written to main memory.  When you release the lock, then 
> main memory is updated.  Random bits of main memory are read into the 
> local cache, but when you aquire an appropriate lock the local cache gets 
> updated.

    Worse, when you release the lock, nothing happens except a marker is 
placed. When another thread tries to acquire a lock, it waits until all 
writes made before markers for that lock complete.

    DS

.