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 8cd839bda8399c50253dfdc7cd008f41d1b5a7f4..6304e2e46c0bd313d0e2603d8e00c46b1731a3c4 100644 (file)
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -174,7 +174,6 @@ static bool streamingDoneReceiving;
 static bool WalSndCaughtUp = false;
 
 /* Flags set by signal handlers for later service in main loop */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t got_SIGUSR2 = false;
 static volatile sig_atomic_t got_STOPPING = false;
 
@@ -190,7 +189,6 @@ static LogicalDecodingContext *logical_decoding_ctx = NULL;
 static XLogRecPtr logical_startptr = InvalidXLogRecPtr;
 
 /* Signal handlers */
-static void WalSndSigHupHandler(SIGNAL_ARGS);
 static void WalSndLastCycleHandler(SIGNAL_ARGS);
 
 /* Prototypes for private functions */
@@ -1104,9 +1102,9 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
            exit(1);
 
        /* Process any requests or signals received recently */
-       if (got_SIGHUP)
+       if (ConfigReloadPending)
        {
-           got_SIGHUP = false;
+           ConfigReloadPending = false;
            ProcessConfigFile(PGC_SIGHUP);
            SyncRepInitConfig();
        }
@@ -1188,9 +1186,9 @@ WalSndWaitForWal(XLogRecPtr loc)
            exit(1);
 
        /* Process any requests or signals received recently */
-       if (got_SIGHUP)
+       if (ConfigReloadPending)
        {
-           got_SIGHUP = false;
+           ConfigReloadPending = false;
            ProcessConfigFile(PGC_SIGHUP);
            SyncRepInitConfig();
        }
@@ -1843,9 +1841,9 @@ WalSndLoop(WalSndSendDataCallback send_data)
            exit(1);
 
        /* Process any requests or signals received recently */
-       if (got_SIGHUP)
+       if (ConfigReloadPending)
        {
-           got_SIGHUP = false;
+           ConfigReloadPending = false;
            ProcessConfigFile(PGC_SIGHUP);
            SyncRepInitConfig();
        }
@@ -2636,19 +2634,6 @@ HandleWalSndInitStopping(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;
-}
-
 /*
  * SIGUSR2: set flag to do a last cycle and shut down afterwards. The WAL
  * sender should already have been switched to WALSNDSTATE_STOPPING at
@@ -2670,7 +2655,7 @@ 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 8b9c3d4feb9ba2356d94fa8a1fd126713884a0bc..7a1b49a92758f0934ac71cbe6a5b034658260580 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -121,13 +121,6 @@ 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.
@@ -196,7 +189,6 @@ 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);
 
 
@@ -2676,13 +2668,19 @@ 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);
 
@@ -3674,8 +3672,8 @@ 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 */
 
@@ -4069,9 +4067,9 @@ 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 342105f0174b233913fec161cfa1014c18fcc88a..67c02f6e4c50f919340c73edbbb2c068ddcaf694 100644 (file)
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -31,6 +31,7 @@ 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 dec110650ec6df4100f85a754f7cb23bab39ac2a..5ecdb255ed3faa6036d0546e32ccb90ed8a80c0f 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 */
 
 
@@ -80,6 +82,7 @@
 extern PGDLLIMPORT volatile bool InterruptPending;
 extern PGDLLIMPORT volatile bool QueryCancelPending;
 extern PGDLLIMPORT volatile bool ProcDiePending;
+extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
 
 extern volatile bool ClientConnectionLost;
 
@@ -270,6 +273,8 @@ 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);