Back-patch assorted latch-related fixes.

Fix a whole bunch of signal handlers that had been hacked to do things that
might change errno, without adding the necessary save/restore logic for
errno.  Also make some minor fixes in unix_latch.c, and clean up bizarre
and unsafe scheme for disowning the process's latch.  While at it, rename
the PGPROC latch field to procLatch for consistency with 9.2.

Issues noted while reviewing a patch by Peter Geoghegan.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index aaa048525b4..bc7b3146b7b 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1188,18 +1188,26 @@ XLogSend(char *msgbuf, bool *caughtup)
 static void
 WalSndSigHupHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	got_SIGHUP = true;
 	if (MyWalSnd)
 		SetLatch(&MyWalSnd->latch);
+
+	errno = save_errno;
 }
 
 /* SIGTERM: set flag to shut down */
 static void
 WalSndShutdownHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	walsender_shutdown_requested = true;
 	if (MyWalSnd)
 		SetLatch(&MyWalSnd->latch);
+
+	errno = save_errno;
 }
 
 /*
@@ -1238,16 +1246,24 @@ WalSndQuickDieHandler(SIGNAL_ARGS)
 static void
 WalSndXLogSendHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	latch_sigusr1_handler();
+
+	errno = save_errno;
 }
 
 /* SIGUSR2: set flag to do a last cycle and shut down afterwards */
 static void
 WalSndLastCycleHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	walsender_ready_to_stop = true;
 	if (MyWalSnd)
 		SetLatch(&MyWalSnd->latch);
+
+	errno = save_errno;
 }
 
 /* Set up signal handlers */