> On 24 Apr 2001, Jeff Trawick wrote:
>
> > > Why is this field going into the scoreboard? This field is really private
> > > to the child process, and doesn't need to go into shared memory.
> > >
> > > Can't the problem describes above be solved with a simple
> > >
> > > workers_may_exit = 1;
> > >
> > > at line 732 of threaded.c?
> >
> > You're at least close to right.
> >
> > You still have the problem that there is nothing to wake up the worker
> > threads; thus we need to write to the pipe of death as done in the
> > patch.
I believe Ryan is right here...
All but one worker should be blocked on the accept mutex (find SAFE_ACCEPT() in
threaded.c). One worker is blocked in apr_poll(). When the parent writes to the pipe
of
death, the thread in apr_poll is awakened and it is able to intuit if the pipe of death
was written to or not, so it calls check_pipe_of_death(). If the pipe_of_death() was
written to, workers_may_exit is set. Then the thread releases the accept mutex and
exits.
The release of the accept mutex allows another thread to enter the locked region. The
very
first thing it does is check workers_may_exit, sees that it is set, releases the accept
mutex and exits. This pattern should repeat untill all the workers have exited at
which
point the main thread pthread_join call fails allowing the main thread to exit.
I don't think we need the workers_may_exit in shared memory because the accept_mutex
guarantees no workers will sneak into the apr_poll() call.
Bill
