From 214c7a4f0b1784ce855512c2961b09c9f51dafd8 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 1 Feb 2014 16:20:56 -0500
Subject: [PATCH] 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.
---
contrib/worker_spi/worker_spi.c | 7 ++++++-
src/backend/replication/walreceiver.c | 4 ++++
src/backend/replication/walsender.c | 18 ++++++++++++------
3 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/contrib/worker_spi/worker_spi.c b/contrib/worker_spi/worker_spi.c
index 23ace7a8afe..560be21814e 100644
--- 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 cc3d7753074..e31977eee02 100644
--- 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 119a920af21..a661d882771 100644
--- 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;
}
/*
--
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