F_SETSIG broken/changed in 2.6 for UDP and TCP sockets?

[Russell Leighton <russ@elegant-software.com>]

I have a program that works fine under stock rh9 (2.4.2-8) but has 
issues getting signaled under FedoraCore2 (2.6.5-1.358)
using SETSIG to a Posix RT signal.

The program does the standard:

  /* hook to process */
  if ( fcntl(fdcallback->fd, F_SETOWN, mon->handler_q.thread->pid) == -1 ) {
    aw_log(fdcallback->handler->logger, AW_ERROR_LOG_LEVEL,
       "cannot set owner on fd (%s)",
       strerror(errno));
  }/* end if */

  /* make async */
  if ( fcntl(fdcallback->fd, F_SETFL, (O_NONBLOCK | O_ASYNC) ) == -1 ) {
    aw_log(fdcallback->handler->logger, AW_ERROR_LOG_LEVEL,
       "cannot set async on fd (%s)",
       strerror(errno));
  }/* end if */

  /* hook to signal */
  if ( fcntl(fdcallback->fd, F_SETSIG, AW_SIG_FD) == -1 ) {
    aw_log(fdcallback->handler->logger, AW_ERROR_LOG_LEVEL,
       "cannot set signal on fd (%s)",
       strerror(errno));
  }/* end if */

Under Fedora things work well for raw sockets (much lower latency than 
in 2.4!) but are inconsistent with udp or tcp sockets.

In the udp case, I when I listen for multicast packets my app only 
receives them when I am running a tcpdump (bizarre!).

In the tcp case, I don't get signaled if I do the F_SETSIG on more than 
1 fd.

Any tips on tracking this down would be much appreciated.

Thx

Russ