Fix some more bugs in signal handlers and process shutdown logic.

WalSndKill was doing things exactly backwards: it should first clear
MyWalSnd (to stop signal handlers from touching MyWalSnd->latch),
then disown the latch, and only then mark the WalSnd struct unused by
clearing its pid field.

Also, WalRcvSigUsr1Handler and worker_spi_sighup failed to preserve
errno, which is surely a requirement for any signal handler.

Per discussion of recent buildfarm failures.  Back-patch as far
as the relevant code exists.

diff --git a/contrib/worker_spi/worker_spi.c b/contrib/worker_spi/worker_spi.c
index 23ace7a8afe5bdee13569851eca79fbaf828db2c..560be21814edc93d77f042294204e6155c2a0ea6 100644 (file)
--- a/contrib/worker_spi/worker_spi.c
+++ b/contrib/worker_spi/worker_spi.c
@@ -42,6 +42,7 @@
 #include "tcop/utility.h"
 
 PG_MODULE_MAGIC;
+
 PG_FUNCTION_INFO_V1(worker_spi_launch);
 
 void           _PG_init(void);
@@ -82,15 +83,19 @@ worker_spi_sigterm(SIGNAL_ARGS)
 
 /*
  * Signal handler for SIGHUP
- *             Set a flag to let the main loop to reread the config file, and set
+ *             Set a flag to tell the main loop to reread the config file, and set
  *             our latch to wake it up.
  */
 static void
 worker_spi_sighup(SIGNAL_ARGS)
 {
+       int                     save_errno = errno;
+
        got_sighup = true;
        if (MyProc)
                SetLatch(&MyProc->procLatch);
+
+       errno = save_errno;
 }
 
 /*

diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index cc3d775307406e95a4d07f59866a2a74fffdd04d..e31977eee02eb51ff5031ffdb0daf09f168c9661 100644 (file)
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -740,7 +740,11 @@ WalRcvSigHupHandler(SIGNAL_ARGS)
 static void
 WalRcvSigUsr1Handler(SIGNAL_ARGS)
 {
+       int                     save_errno = errno;
+
        latch_sigusr1_handler();
+
+       errno = save_errno;
 }
 
 /* SIGTERM: set flag for main loop, or shutdown immediately if safe */

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 119a920af215b1c600b2239dd534111d41b6f31b..a661d8827715fca85a3467459e225a8f691c60d9 100644 (file)
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1401,17 +1401,23 @@ InitWalSenderSlot(void)
 static void
 WalSndKill(int code, Datum arg)
 {
-       Assert(MyWalSnd != NULL);
+       WalSnd     *walsnd = MyWalSnd;
+
+       Assert(walsnd != NULL);
+
+       /*
+        * Clear MyWalSnd first; then disown the latch.  This is so that signal
+        * handlers won't try to touch the latch after it's no longer ours.
+        */
+       MyWalSnd = NULL;
+
+       DisownLatch(&walsnd->latch);
 
        /*
         * Mark WalSnd struct no longer in use. Assume that no lock is required
         * for this.
         */
-       MyWalSnd->pid = 0;
-       DisownLatch(&MyWalSnd->latch);
-
-       /* WalSnd struct isn't mine anymore */
-       MyWalSnd = NULL;
+       walsnd->pid = 0;
 }
 
 /*