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.

1 files changed, 11 insertions, 39 deletions

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index 49bd6d07e51..6a68af49d3e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.55 1998/07/03 04:24:13 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.56 1998/07/09 03:29:08 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -361,6 +361,16 @@ parseInput(PGconn *conn)
 														 PGRES_EMPTY_QUERY);
 					conn->asyncStatus = PGASYNC_READY;
 					break;
+				case 'K':		/* secret key data from the backend */
+					/* This is expected only during backend startup,
+					 * but it's just as easy to handle it as part of the
+					 * main loop.  Save the data and continue processing.
+					 */
+					if (pqGetInt(&(conn->be_pid), 4, conn))
+						return;
+					if (pqGetInt(&(conn->be_key), 4, conn))
+						return;
+					break;
 				case 'N':		/* notices from the backend */
 					if (getNotice(conn))
 						return;
@@ -762,44 +772,6 @@ PQexec(PGconn *conn, const char *query)
 
 
 /*
- * Attempt to request cancellation of the current operation.
- *
- * The return value is TRUE if the cancel request was successfully
- * dispatched, FALSE if not (in which case errorMessage is set).
- * Note: successful dispatch is no guarantee that there will be any effect at
- * the backend.  The application must read the operation result as usual.
- */
-
-int
-PQrequestCancel(PGconn *conn)
-{
-	char msg[1];
-
-	if (!conn)
-		return FALSE;
-
-	if (conn->sock < 0)
-	{
-		sprintf(conn->errorMessage,
-				"PQrequestCancel() -- connection is not open\n");
-		return FALSE;
-	}
-
-	msg[0] = '\0';
-
-	if (send(conn->sock, msg, 1, MSG_OOB) < 0)
-	{
-		sprintf(conn->errorMessage,
-				"PQrequestCancel() -- couldn't send OOB data: errno=%d\n%s\n",
-				errno, strerror(errno));
-		return FALSE;
-	}
-
-	return TRUE;
-}
-
-
-/*
  * Attempt to read a Notice response message.
  * This is possible in several places, so we break it out as a subroutine.
  * Entry: 'N' flag character has already been consumed.