Unify SIGHUP handling between normal and walsender backends.

anarazel · anarazel · commit 45d067d50d8e · 2017-06-05T19:18:16.000-07:00
Because walsender and normal backends share the same main loop it's problematic to have two different flag variables, set in signal handlers, indicating a pending configuration reload. Only certain walsender commands reach code paths checking for the variable (START_[LOGICAL_]REPLICATION, CREATE_REPLICATION_SLOT ... LOGICAL, notably not base backups). This is a bug present since the introduction of walsender, but has gotten worse in releases since then which allow walsender to do more. A later patch, not slated for v10, will similarly unify SIGHUP handling in other types of processes as well. Author: Petr Jelinek, Andres Freund Reviewed-By: Michael Paquier Discussion: https://postgr.es/m/20170423235941.qosiuoyqprq4nu7v@alap3.anarazel.de Backpatch: 9.2-, bug is present since 9.0
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
@@ -166,7 +166,6 @@ static volatile sig_atomic_t walsender_ready_to_stop = false;
 static volatile sig_atomic_t replication_active = false;
 
 /* Signal handlers */
-static void WalSndSigHupHandler(SIGNAL_ARGS);
 static void WalSndXLogSendHandler(SIGNAL_ARGS);
 static void WalSndLastCycleHandler(SIGNAL_ARGS);
 
@@ -979,9 +978,9 @@ WalSndLoop(void)
 			exit(1);
 
 		/* Process any requests or signals received recently */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			SyncRepInitConfig();
 		}
@@ -1712,19 +1711,6 @@ WalSndRqstFileReload(void)
 	}
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-WalSndSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	if (MyWalSnd)
-		SetLatch(&MyWalSnd->latch);
-
-	errno = save_errno;
-}
-
 /* SIGUSR1: set flag to send WAL records */
 static void
 WalSndXLogSendHandler(SIGNAL_ARGS)
@@ -1763,7 +1749,7 @@ void
 WalSndSignals(void)
 {
 	/* Set up signal handlers */
-	pqsignal(SIGHUP, WalSndSigHupHandler);		/* set flag to read config
+	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config
 												 * file */
 	pqsignal(SIGINT, SIG_IGN);	/* not used */
 	pqsignal(SIGTERM, die);		/* request shutdown */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
@@ -130,13 +130,6 @@ char	   *stack_base_ptr = NULL;
 char	   *register_stack_base_ptr = NULL;
 #endif
 
-/*
- * Flag to mark SIGHUP. Whenever the main loop comes around it
- * will reread the configuration file. (Better than doing the
- * reading in the signal handler, ey?)
- */
-static volatile sig_atomic_t got_SIGHUP = false;
-
 /*
  * Flag to keep track of whether we have started a transaction.
  * For extended query protocol this has to be remembered across messages.
@@ -205,7 +198,6 @@ static bool IsTransactionExitStmt(Node *parsetree);
 static bool IsTransactionExitStmtList(List *parseTrees);
 static bool IsTransactionStmtList(List *parseTrees);
 static void drop_unnamed_stmt(void);
-static void SigHupHandler(SIGNAL_ARGS);
 static void log_disconnections(int code, Datum arg);
 
 
@@ -2685,13 +2677,19 @@ FloatExceptionHandler(SIGNAL_ARGS)
 					   "invalid operation, such as division by zero.")));
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-SigHupHandler(SIGNAL_ARGS)
+/*
+ * SIGHUP: set flag to re-read config file at next convenient time.
+ *
+ * Sets the ConfigReloadPending flag, which should be checked at convenient
+ * places inside main loops. (Better than doing the reading in the signal
+ * handler, ey?)
+ */
+void
+PostgresSigHupHandler(SIGNAL_ARGS)
 {
 	int			save_errno = errno;
 
-	got_SIGHUP = true;
+	ConfigReloadPending = true;
 	if (MyProc)
 		SetLatch(&MyProc->procLatch);
 
@@ -3683,8 +3681,8 @@ PostgresMain(int argc, char *argv[],
 		WalSndSignals();
 	else
 	{
-		pqsignal(SIGHUP, SigHupHandler);		/* set flag to read config
-												 * file */
+		pqsignal(SIGHUP, PostgresSigHupHandler);		/* set flag to read config
+														 * file */
 		pqsignal(SIGINT, StatementCancelHandler);		/* cancel current query */
 		pqsignal(SIGTERM, die); /* cancel current query and exit */
 
@@ -4062,9 +4060,9 @@ PostgresMain(int argc, char *argv[],
 		 * (5) check for any other interesting events that happened while we
 		 * slept.
 		 */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
@@ -30,6 +30,7 @@ volatile bool QueryCancelPending = false;
 volatile bool ProcDiePending = false;
 volatile bool ClientConnectionLost = false;
 volatile bool ImmediateInterruptOK = false;
+volatile sig_atomic_t ConfigReloadPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
@@ -23,6 +23,8 @@
 #ifndef MISCADMIN_H
 #define MISCADMIN_H
 
+#include <signal.h>
+
 #include "pgtime.h"				/* for pg_time_t */
 
 
@@ -78,6 +80,7 @@
 extern PGDLLIMPORT volatile bool InterruptPending;
 extern volatile bool QueryCancelPending;
 extern volatile bool ProcDiePending;
+extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
 
 extern volatile bool ClientConnectionLost;
 
@@ -276,6 +279,8 @@ extern void restore_stack_base(pg_stack_base_t base);
 extern void check_stack_depth(void);
 extern bool stack_is_too_deep(void);
 
+extern void PostgresSigHupHandler(SIGNAL_ARGS);
+
 /* in tcop/utility.c */
 extern void PreventCommandIfReadOnly(const char *cmdname);
 extern void PreventCommandDuringRecovery(const char *cmdname);
