Re: Subtle MM bug

[Stephen C. Tweedie]

Hi,

On Thu, Jan 11, 2001 at 02:03:48PM -0500, Alexander Viro wrote:
> On Thu, 11 Jan 2001, Stephen C. Tweedie wrote:
> 
> > On Thu, Jan 11, 2001 at 02:12:05PM +0100, Trond Myklebust wrote:
> > > 
> > >  What's wrong with copy-on-write style semantics? IOW, anyone who
> > > wants to change the credentials needs to make a private copy of the
> > > existing structure first.
> > 
> > Because COW only solves the problem if each task is only changing its
> > own, local, private copy of the credentials.  Posix threads demand
> > that one thread changing credentials also affects all the other
> > threads immediately, and making your own local private copy won't help
> > you to change the other tasks' credentials safely.
> 
> And how is that different from the current situation?

It's not, which is the point I was making: COW doesn't actually solve
the pthreads problem.  Far better to do it in user space.

--Stephen