call previous signal handler with raise(3) is not synchronous

My program uses a library that installs a SIGHUP handler. I need to add another handler.

I found here: http://stackoverflow.com/a/13290134/447503 a suggestion to restore the original handler and call raise() , then restore my handler.

It's considered better, because you don't need to check for three-args or one-arg version of the handler and for SIG_DFL and SIG_IGN in your code.

However, raise() returns before the original hadler is called. I restore my handler and only then my program receives the signal I just sent. So the program enters infinite loop.

PrevSigHupSignalHandler = sigset(SIGHUP,SgpCacheRefreshSignalHandler);

static void SgpCacheRefreshSignalHandler(int signo)
{
  signal(SIGHUP, PrevSigHupSignalHandler);
  raise(SIGHUP);
  /* when it returns here .. set our signal handler again */
  signal(SIGHUP, SgpCacheRefreshSignalHandler);
}