Ensure that 'errno' is saved and restored by all signal handlers that

might change it.  Experimentation shows that the signal handler call
mechanism does not save/restore errno for you, at least not on Linux
or HPUX, so this is definitely a real risk.

src/backend/commands/async.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.73 2000/11/28 23:27:54 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.74 2000/12/18 17:33:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -589,6 +589,7 @@ AtAbort_Notify()
 void
 Async_NotifyHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
 
 	/*
 	 * Note: this is a SIGNAL HANDLER.	You must be very wary what you do
@@ -637,6 +638,8 @@ Async_NotifyHandler(SIGNAL_ARGS)
 		 */
 		notifyInterruptOccurred = 1;
 	}
+
+	errno = save_errno;
 }
 
 /*

src/backend/postmaster/postmaster.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.198 2000/12/03 20:45:34 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.199 2000/12/18 17:33:40 tgl Exp $
  *
  * NOTES
  *
@@ -217,7 +217,7 @@ static int	initMasks(fd_set *rmask, fd_set *wmask);
 static char *canAcceptConnections(void);
 static long PostmasterRandom(void);
 static void RandomSalt(char *salt);
-static void SignalChildren(SIGNAL_ARGS);
+static void SignalChildren(int signal);
 static int	CountChildren(void);
 static bool CreateOptsFile(int argc, char *argv[]);
 
@@ -1303,10 +1303,13 @@ reset_shared(unsigned short port)
 static void
 SIGHUP_handler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	if (Shutdown > SmartShutdown)
 		return;
 	got_SIGHUP = true;
 	SignalChildren(SIGHUP);
+	errno = save_errno;
 }
 
 
@@ -1317,6 +1320,8 @@ SIGHUP_handler(SIGNAL_ARGS)
 static void
 pmdie(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	PG_SETMASK(&BlockSig);
 
 	if (DebugLvl >= 1)
@@ -1330,8 +1335,12 @@ pmdie(SIGNAL_ARGS)
 			 * Send SIGUSR2 to all children (AsyncNotifyHandler)
 			 */
 			if (Shutdown > SmartShutdown)
+			{
+				errno = save_errno;
 				return;
+			}
 			SignalChildren(SIGUSR2);
+			errno = save_errno;
 			return;
 
 		case SIGTERM:
@@ -1342,24 +1351,34 @@ pmdie(SIGNAL_ARGS)
 			 * let children to end their work and ShutdownDataBase.
 			 */
 			if (Shutdown >= SmartShutdown)
+			{
+				errno = save_errno;
 				return;
+			}
 			Shutdown = SmartShutdown;
 			tnow = time(NULL);
 			fprintf(stderr, "Smart Shutdown request at %s", ctime(&tnow));
 			fflush(stderr);
 			if (DLGetHead(BackendList)) /* let reaper() handle this */
+			{
+				errno = save_errno;
 				return;
+			}
 
 			/*
 			 * No children left. Shutdown data base system.
 			 */
 			if (StartupPID > 0 || FatalError)	/* let reaper() handle
 												 * this */
+			{
+				errno = save_errno;
 				return;
+			}
 			if (ShutdownPID > 0)
 				abort();
 
 			ShutdownPID = ShutdownDataBase();
+			errno = save_errno;
 			return;
 
 		case SIGINT:
@@ -1371,7 +1390,10 @@ pmdie(SIGNAL_ARGS)
 			 * and exit) and ShutdownDataBase.
 			 */
 			if (Shutdown >= FastShutdown)
+			{
+				errno = save_errno;
 				return;
+			}
 			tnow = time(NULL);
 			fprintf(stderr, "Fast Shutdown request at %s", ctime(&tnow));
 			fflush(stderr);
@@ -1384,11 +1406,13 @@ pmdie(SIGNAL_ARGS)
 					fflush(stderr);
 					SignalChildren(SIGTERM);
 				}
+				errno = save_errno;
 				return;
 			}
 			if (Shutdown > NoShutdown)
 			{
 				Shutdown = FastShutdown;
+				errno = save_errno;
 				return;
 			}
 			Shutdown = FastShutdown;
@@ -1398,11 +1422,15 @@ pmdie(SIGNAL_ARGS)
 			 */
 			if (StartupPID > 0 || FatalError)	/* let reaper() handle
 												 * this */
+			{
+				errno = save_errno;
 				return;
+			}
 			if (ShutdownPID > 0)
 				abort();
 
 			ShutdownPID = ShutdownDataBase();
+			errno = save_errno;
 			return;
 
 		case SIGQUIT:
@@ -1435,18 +1463,18 @@ pmdie(SIGNAL_ARGS)
 static void
 reaper(SIGNAL_ARGS)
 {
-/* GH: replace waitpid for !HAVE_WAITPID. Does this work ? */
+	int			save_errno = errno;
 #ifdef HAVE_WAITPID
 	int			status;			/* backend exit status */
-
 #else
 	union wait	status;			/* backend exit status */
-
 #endif
 	int			exitstatus;
 	int			pid;			/* process id of dead backend */
 
 	PG_SETMASK(&BlockSig);
+	/* It's not really necessary to reset the handler each time is it? */
+	pqsignal(SIGCHLD, reaper);
 
 	if (DebugLvl)
 		fprintf(stderr, "%s: reaping dead processes...\n",
@@ -1499,12 +1527,11 @@ reaper(SIGNAL_ARGS)
 			CheckPointPID = 0;
 			checkpointed = time(NULL);
 
-			pqsignal(SIGCHLD, reaper);
+			errno = save_errno;
 			return;
 		}
 		CleanupProc(pid, exitstatus);
 	}
-	pqsignal(SIGCHLD, reaper);
 
 	if (FatalError)
 	{
@@ -1513,9 +1540,15 @@ reaper(SIGNAL_ARGS)
 		 * Wait for all children exit, then reset shmem and StartupDataBase.
 		 */
 		if (DLGetHead(BackendList))
+		{
+			errno = save_errno;
 			return;
+		}
 		if (StartupPID > 0 || ShutdownPID > 0)
+		{
+			errno = save_errno;
 			return;
+		}
 		tnow = time(NULL);
 		fprintf(stderr, "Server processes were terminated at %s"
 				"Reinitializing shared memory and semaphores\n",
@@ -1526,18 +1559,26 @@ reaper(SIGNAL_ARGS)
 		reset_shared(PostPortNumber);
 
 		StartupPID = StartupDataBase();
+		errno = save_errno;
 		return;
 	}
 
 	if (Shutdown > NoShutdown)
 	{
 		if (DLGetHead(BackendList))
+		{
+			errno = save_errno;
 			return;
+		}
 		if (StartupPID > 0 || ShutdownPID > 0)
+		{
+			errno = save_errno;
 			return;
+		}
 		ShutdownPID = ShutdownDataBase();
 	}
 
+	errno = save_errno;
 }
 
 /*
@@ -2002,6 +2043,7 @@ ExitPostmaster(int status)
 static void
 dumpstatus(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
 	Dlelem	   *curr;
 
 	PG_SETMASK(&BlockSig);
@@ -2015,6 +2057,7 @@ dumpstatus(SIGNAL_ARGS)
 		fprintf(stderr, "\tsock %d\n", port->sock);
 		curr = DLGetSucc(curr);
 	}
+	errno = save_errno;
 }
 
 /*

src/backend/storage/lmgr/proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.87 2000/12/18 00:44:47 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.88 2000/12/18 17:33:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,10 +48,11 @@
  *		This is so that we can support more backends. (system-wide semaphore
  *		sets run out pretty fast.)				  -ay 4/95
  *
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.87 2000/12/18 00:44:47 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.88 2000/12/18 17:33:41 tgl Exp $
  */
 #include "postgres.h"
 
+#include <errno.h>
 #include <sys/time.h>
 #include <unistd.h>
 #include <signal.h>
@@ -298,7 +299,7 @@ InitProcess(void)
 }
 
 /* -----------------------
- * get off the wait queue
+ * get process off any wait queue it might be on
  * -----------------------
  */
 static bool
@@ -623,10 +624,11 @@ ins:;
 	waitQueue->size++;
 
 	lock->waitMask |= myMask;
-	SpinRelease(spinlock);
 
 	MyProc->errType = NO_ERROR;		/* initialize result for success */
 
+	SpinRelease(spinlock);
+
 	/* --------------
 	 * Set timer so we can wake up after awhile and check for a deadlock.
 	 * If a deadlock is detected, the handler releases the process's
@@ -826,6 +828,7 @@ ProcAddLock(SHM_QUEUE *elem)
 void
 HandleDeadLock(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
 	LOCK	   *mywaitlock;
 
 	LockLockTable();
@@ -846,6 +849,7 @@ HandleDeadLock(SIGNAL_ARGS)
 		MyProc->links.next == INVALID_OFFSET)
 	{
 		UnlockLockTable();
+		errno = save_errno;
 		return;
 	}
 
@@ -858,6 +862,7 @@ HandleDeadLock(SIGNAL_ARGS)
 	{
 		/* No deadlock, so keep waiting */
 		UnlockLockTable();
+		errno = save_errno;
 		return;
 	}
 
@@ -891,6 +896,7 @@ HandleDeadLock(SIGNAL_ARGS)
 	 * conditions.	i don't claim to understand this...
 	 */
 	UnlockLockTable();
+	errno = save_errno;
 }
 
 void

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.195 2000/12/18 00:44:47 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.196 2000/12/18 17:33:41 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -984,8 +984,11 @@ FloatExceptionHandler(SIGNAL_ARGS)
 static void
 QueryCancelHandler(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	QueryCancel = true;
 	LockWaitCancel();
+	errno = save_errno;
 }
 
 void
@@ -1646,7 +1649,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[], const cha
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.195 $ $Date: 2000/12/18 00:44:47 $\n");
+		puts("$Revision: 1.196 $ $Date: 2000/12/18 17:33:41 $\n");
 	}
 
 	/*

src/bin/psql/common.c

@@ -3,7 +3,7 @@
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  *
- * $Header: /cvsroot/pgsql/src/bin/psql/common.c,v 1.28 2000/12/15 17:54:43 petere Exp $
+ * $Header: /cvsroot/pgsql/src/bin/psql/common.c,v 1.29 2000/12/18 17:33:42 tgl Exp $
  */
 #include "postgres.h"
 #include "common.h"
@@ -258,6 +258,8 @@ volatile bool cancel_pressed;
 void
 handle_sigint(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	/* Don't muck around if copying in or prompting for a password. */
 	if ((copy_in_state && pset.cur_cmd_interactive) || prompt_state)
 		return;
@@ -274,6 +276,7 @@ handle_sigint(SIGNAL_ARGS)
 		write_stderr("Could not send cancel request: ");
 		write_stderr(PQerrorMessage(cancelConn));
 	}
+	errno = save_errno;			/* just in case the write changed it */
 }
 
 #endif	 /* not WIN32 */

src/interfaces/libpq/fe-connect.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.154 2000/12/07 02:04:30 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.155 2000/12/18 17:33:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2084,6 +2084,7 @@ PQresetPoll(PGconn *conn)
  * malloc/free are often non-reentrant, and anything that might call them is
  * just as dangerous.  We avoid sprintf here for that reason.  Building up
  * error messages with strcpy/strcat is tedious but should be quite safe.
+ * We also save/restore errno in case the signal handler support doesn't.
  *
  * NOTE: this routine must not generate any error message longer than
  * INITIAL_EXPBUFFER_SIZE (currently 256), since we dare not try to
@@ -2093,6 +2094,7 @@ PQresetPoll(PGconn *conn)
 int
 PQrequestCancel(PGconn *conn)
 {
+	int			save_errno = errno;
 	int			tmpsock = -1;
 	struct
 	{
@@ -2109,6 +2111,7 @@ PQrequestCancel(PGconn *conn)
 		strcpy(conn->errorMessage.data,
 			   "PQrequestCancel() -- connection is not open\n");
 		conn->errorMessage.len = strlen(conn->errorMessage.data);
+		errno = save_errno;
 		return FALSE;
 	}
 
@@ -2154,6 +2157,7 @@ PQrequestCancel(PGconn *conn)
 	close(tmpsock);
 #endif
 
+	errno = save_errno;
 	return TRUE;
 
 cancel_errReturn:
@@ -2168,6 +2172,7 @@ cancel_errReturn:
 		close(tmpsock);
 #endif
 	}
+	errno = save_errno;
 	return FALSE;
 }