Avoid extra system calls to block SIGPIPE if the platform provides either

sockopt(SO_NOSIGPIPE) or the MSG_NOSIGNAL flag to send().

We assume these features are available if (1) the symbol is defined at
compile time and (2) the kernel doesn't reject the call at runtime.
It might turn out that there are some platforms where (1) and (2) are
true and yet the signal isn't really blocked, in which case applications
would die on server crash.  If that sort of thing gets reported, then
we'll have to add additional defenses of some kind.

Jeremy Kerr

1 files changed, 42 insertions, 2 deletions

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index d20d0b60106..41c753a4f8c 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.375 2009/06/11 14:49:13 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.376 2009/07/24 17:58:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1018,6 +1018,7 @@ PQconnectPoll(PGconn *conn)
 {
 	PGresult   *res;
 	char		sebuf[256];
+	int			optval;
 
 	if (conn == NULL)
 		return PGRES_POLLING_FAILED;
@@ -1153,6 +1154,46 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif   /* F_SETFD */
 
+					/*----------
+					 * We have three methods of blocking SIGPIPE during
+					 * send() calls to this socket:
+					 *
+					 *  - setsockopt(sock, SO_NOSIGPIPE)
+					 *  - send(sock, ..., MSG_NOSIGNAL)
+					 *  - setting the signal mask to SIG_IGN during send()
+					 *
+					 * The third method requires three syscalls per send,
+					 * so we prefer either of the first two, but they are
+					 * less portable.  The state is tracked in the following
+					 * members of PGconn:
+					 *
+					 * conn->sigpipe_so		- we have set up SO_NOSIGPIPE
+					 * conn->sigpipe_flag	- we're specifying MSG_NOSIGNAL
+					 *
+					 * If we can use SO_NOSIGPIPE, then set sigpipe_so here
+					 * and we're done.  Otherwise, set sigpipe_flag so that
+					 * we will try MSG_NOSIGNAL on sends.  If we get an error
+					 * with MSG_NOSIGNAL, we'll clear that flag and revert to
+					 * signal masking.
+					 *----------
+					 */
+					conn->sigpipe_so = false;
+#ifdef MSG_NOSIGNAL
+					conn->sigpipe_flag = true;
+#else
+					conn->sigpipe_flag = false;
+#endif /* MSG_NOSIGNAL */
+
+#ifdef SO_NOSIGPIPE
+					optval = 1;
+					if (setsockopt(conn->sock, SOL_SOCKET, SO_NOSIGPIPE,
+								   (char *) &optval, sizeof(optval)) == 0)
+					{
+						conn->sigpipe_so = true;
+						conn->sigpipe_flag = false;
+					}
+#endif /* SO_NOSIGPIPE */
+
 					/*
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
@@ -1214,7 +1255,6 @@ keep_going:						/* We will come back to here until there is
 
 		case CONNECTION_STARTED:
 			{
-				int			optval;
 				ACCEPT_TYPE_ARG3 optlen = sizeof(optval);
 
 				/*