[patch] Fix Linux attach to signalled/stopped processes

[Roland McGrath]

> > In practice you will 99.44% of the time be able to find some RT signal
> > that is not blocked.  But to worry about the 0.66% you still have to
> > fall back to SIGSTOP, and in that case you can't rely on queuing.
> 
> Wouldn't this be racy, again?  If the process is running, it might be
> about to block the signal we chose to stop it.

Yes.