From: Tom Lane <tgl@sss.pgh.pa.us>

Making PQrequestCancel safe to call in a signal handler turned out to be
much easier than I feared.  So here are the diffs.

Some notes:
  * I modified the postmaster's packet "iodone" callback interface to allow
    the callback routine to return a continue-or-drop-connection return
    code; this was necessary to allow the connection to be closed after
    receiving a Cancel, rather than proceeding to launch a new backend...
    Being a neatnik, I also made the iodone proc have a typechecked
    parameter list.
  * I deleted all code I could find that had to do with OOB.
  * I made some edits to ensure that all signals mentioned in the code
    are referred to symbolically not by numbers ("SIGUSR2" not "2").
    I think Bruce may have already done at least some of the same edits;
    I hope that merging these patches is not too painful.

src/man/listen.l

@@ -1,6 +1,6 @@
 .\" This is -*-nroff-*-
 .\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/src/man/Attic/listen.l,v 1.6 1998/06/24 13:21:27 momjian Exp $
+.\" $Header: /cvsroot/pgsql/src/man/Attic/listen.l,v 1.7 1998/07/09 03:29:09 scrappy Exp $
 .TH "LISTEN" SQL 03/12/94 PostgreSQL PostgreSQL
 .SH NAME
 listen - listen for notification on a relation
@@ -21,9 +21,7 @@ is cleared.
 .PP
 This event notification is performed through the Libpq protocol
 and frontend application interface.  The application program 
-must explicitly poll a Libpq global variable, 
-.IR PQAsyncNotifyWaiting ,
-and call the routine
+must call the routine
 .IR PQnotifies
 in order to find out the name of the class to which a given 
 notification corresponds.  If this code is not included in 

src/man/notify.l

@@ -1,6 +1,6 @@
 .\" This is -*-nroff-*-
 .\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/src/man/Attic/notify.l,v 1.4 1998/06/24 13:21:27 momjian Exp $
+.\" $Header: /cvsroot/pgsql/src/man/Attic/notify.l,v 1.5 1998/07/09 03:29:11 scrappy Exp $
 .TH "NOTIFY" SQL 11/05/95 PostgreSQL PostgreSQL
 .SH NAME
 notify - signal all frontends and backends listening on a class
@@ -32,11 +32,14 @@ does is indicate that some backend wishes its peers to examine
 .IR class_name
 in some application-specific way.
 .PP
+In fact,
+.IR class_name
+need not be the name of an SQL class at all.  It is best thought of
+as a condition name that the application programmer selects.
+.PP
 This event notification is performed through the Libpq protocol
 and frontend application interface.  The application program
-must explicitly poll a Libpq global variable,
-.IR PQAsyncNotifyWaiting ,
-and call the routine
+must call the routine
 .IR PQnotifies
 in order to find out the name of the class to which a given
 notification corresponds.  If this code is not included in