Re: [9fans] waitfor() call question?

["Bruce Ellis" <bruce.ellis@gmail.com>]

the culprit, not the scene of the crime.

brucee

On 10/13/06, Russ Cox <rsc@swtch.com> wrote:
> > Nemo's book (http://lsub.org/who/nemo/9.intro.pdf, page 91) gives code
> > for waiting for a particular descendant process if that's what's
> > wanted.  Actually, he uses it for the immediate child process, which
> > makes me wonder—after the child process has exited, can the parent
> > wait() for a grandchild?
>
> Nope.
>
> > Why is waitfor() "occasionally unavoidable" on UNIX?
>
> Because sometimes what would be multiple processes on Plan 9
> is a single process on Unix, depending on the implementation of
> the thread library, and two shared-memory procs each waiting for
> their own children need not to get the other's child.
> You could have some shared list of accidentally-waited-for children
> but then the coordination to wake up the guy who is actually
> waiting gets cumbersome.
>
> Russ
>