It semms that my suggestion will still not always fix the problem.
There is still an ABA problem, Because the descriptor that just died
could already be reused for a different purpose. So I changed the code
to retry several times until it fails. This fixed the deadlocks so far.
Unfortunately the native OS/2 select implementation has a different
interface. So the code is not 1:1 portable.
On 17.03.12 10.13, Marcel M?ller wrote:
> If select() in the implementation of pa_poll returns an error because of
> an invalid socket, pa_poll tries to find out which descriptor is bad.
> And then retries the select. But this is still in not synchronized
> context. So a second descriptor may become bad on the second call to
> select. This is not captured. And consequently pa_poll fails and the
> mainloop terminates, resulting in deadlocks if further activity is on
> the way.
> It seems that I managed to trigger this problem on OS/2 from time to
> time when closing a pa_stream and a pa_context and opening another
> context at almost the same time.
>
> I would recommend to jump to the previous select() call instead of
> executing another one without error checking. To avoid infinite loops
> this should only be done if the check removed at least one descriptor.
-----
#if defined(OS_IS_OS2)
int pa_poll (struct pollfd *fds, unsigned long int nfds, int timeout) {
int* selectfds;
int nselectfds;
struct pollfd* f;
struct pollfd* fdsend = fds + nfds;
int nreads, nwrites, nexcepts;
int* pselectfd;
int ready;
int nretry = nfds;
/* First check how many descriptors we need */
nselectfds = 0;
for (f = fds; f != fdsend; ++f)
{ int events = f->events;
nselectfds += !!(events & POLLIN)
+ !!(events & POLLPRI)
+ !!(events & POLLOUT);
f->revents = 0;
}
selectfds = alloca(nselectfds * sizeof *selectfds);
retry:
/* populate selectfds */
nreads = 0;
nwrites = 0;
nexcepts = 0;
pselectfd = selectfds;
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLIN)
{ *pselectfd++ = f->fd;
++nreads;
}
}
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLOUT)
{ *pselectfd++ = f->fd;
++nwrites;
}
}
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLPRI)
{ *pselectfd++ = f->fd;
++nexcepts;
}
}
/* execute select */
ready = os2_select(selectfds, nreads, nwrites, nexcepts, timeout);
if (ready == -1)
{ errno = sock_errno();
/* One of the descriptors is bad. Find out which one. */
int removed = 0;
for (f = fds; f != fdsend; ++f)
if (f->events != 0)
{ if (os2_select(&f->fd, 1, 0, 0, 0) == -1)
{ /* do not care any more */
f->events = 0;
++removed;
}
}
DEBUGLOG(("pa_poll - recover? %i\n", removed));
if (nretry)
{ --nretry;
goto retry;
}
} else if (ready)
{ /* Find out the descriptors that got ready. */
ready = 0;
pselectfd = selectfds;
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLIN)
{ if (*pselectfd++ != -1)
{ ++ready;
f->revents = POLLIN;
}
}
}
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLOUT)
{ if (*pselectfd++ != -1)
{ if (!f->revents)
++ready;
f->revents |= POLLOUT;
}
}
}
for (f = fds; f != fdsend; ++f)
{ if (f->events & POLLPRI)
{ if (*pselectfd++ != -1)
{ if (!f->revents)
++ready;
f->revents |= POLLPRI;
}
}
}
}
return ready;
}
#elif !defined(HAVE_POLL_H) || defined(OS_IS_DARWIN)
