Re: Several questions.

[Michael Livshin]

Marius Vollmer <address@hidden> writes:

> Dirk Herrmann <address@hidden> writes:
> 
> > On 20 Apr 2001, Marius Vollmer wrote:
> > 
> > > > * scm_smobs is a malloc'd array that gets resized for every new
> > > >   smob.  With preemptive threading, this will not work well:  It would 
> > > > be
> > > >   necessary to guard every access to scm_smobs with a mutex.
> > > 
> > > Does pthreads offer something like a atomic update for a pointer?
> > > With such a thing, we could atomically swap in the new smobtable.
> > 
> > I don't think so.  The problem does not depend on whether the pointer can
> > be updated atomically.

just a small point: while the POSIX spec doesn't guarantee (or specify
a way to get) memory coherence (i.e. atomic updates) in general, all
the interesting platforms update word-sized (and word-aligned, of
course) locations atomically.  ISTR that Java counts on it.

this is from memory, though.

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