postgres.git / summary / log / commit / refs

commit    6f1a4077310e97fe32379263918a31b95f85e2ed
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Sat Feb 01 21:21:00 2014 +0000
First released in: 9.4.0, 9.1.12, 9.2.7, 9.3.3

    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       |  6 +++++-
 src/backend/replication/walreceiver.c |  4 ++++
 src/backend/replication/walsender.c   | 18 ++++++++++++------
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/contrib/worker_spi/worker_spi.c b/contrib/worker_spi/worker_spi.c
index 99501fa5668..beffab1cad2 100644
--- a/contrib/worker_spi/worker_spi.c
+++ b/contrib/worker_spi/worker_spi.c
@@ -79,15 +79,19 @@ 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 7fe80a94a30..ae087535f78 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -737,7 +737,11 @@ 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 afd559dae46..cdd9c6a5334 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1214,17 +1214,23 @@ 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;
 }
 
 /*


[parent: 27942baf49eb]