Add description of the deadlock problem with child processes and pipes, and
hints about how to work around it.
Closes SF bug #530637.
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index f234e13..33c1e54 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -339,6 +339,11 @@
\class{Popen3} and \class{Popen4} classes from the \refmodule{popen2}
module; these are only available on \UNIX.
+For a discussion of possible dead lock conditions related to the use
+of these functions, see ``\ulink{Flow Control
+Issues}{popen2-flow-control.html}''
+(section~\ref{popen2-flow-control}).
+
\begin{funcdesc}{popen2}{cmd\optional{, mode\optional{, bufsize}}}
Executes \var{cmd} as a sub-process. Returns the file objects
\code{(\var{child_stdin}, \var{child_stdout})}.