Unify SIGHUP handling between normal and walsender backends.

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
index 9b455eef58579269a45ade70e721cfd6d89ba2f6..14ad50b737e7bf6256b4c084a93eed7bc909c5a9 100644 (file)
--- 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
index 4c140ee3154fc452e792f87e9556af5a64de1af2..538f9f3d32d966df644d26a8983815d85ef15e40 100644 (file)
--- 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
index 10463c6703dc56a0aec719cced1b1640aedc8f39..80e30833549751ba10ce172080ce0befeb44a5d9 100644 (file)
--- 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
index f88a49183b311c4cbc41ef4cf5aafe73f0491e38..d0ec3914e08d07b3f41c6a4d6c8995653e089d02 100644 (file)
--- 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);