Leave SIGTTIN/SIGTTOU signal handling alone in postmaster child processes.

For reasons lost in the mists of time, most postmaster child processes
reset SIGTTIN/SIGTTOU signal handling to SIG_DFL, with the major exception
that backend sessions do not.  It seems like a pretty bad idea for any
postmaster children to do that: if stderr is connected to the terminal,
and the user has put the postmaster in background, any log output would
result in the child process freezing up.  Hence, switch them all to
doing what backends do, ie, nothing.  This allows them to inherit the
postmaster's SIG_IGN setting.  On the other hand, manually-launched
processes such as standalone backends will have default processing,
which seems fine.

In passing, also remove useless resets of SIGCONT and SIGWINCH signal
processing.  Perhaps the postmaster once changed those to something
besides SIG_DFL, but it doesn't now, so these are just wasted (and
confusing) syscalls.

Basically, this propagates the changes made in commit 8e2998d8a from
backends to other postmaster children.  Probably the only reason these
calls now exist elsewhere is that I missed changing pgstat.c along with
postgres.c at the time.

Given the lack of field complaints that can be traced to this, I don't
presently feel a need to back-patch.

Discussion: https://postgr.es/m/[email protected]

10 files changed, 11 insertions, 36 deletions

diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index b1e9bb2c537..54a042843da 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -133,10 +133,6 @@ BackgroundWriterMain(void)
 	 * Reset some signals that are accepted by postmaster but not here
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	/* We allow SIGQUIT (quickdie) at all times */
 	sigdelset(&BlockSig, SIGQUIT);
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 1a033093c53..9eac86b554b 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -218,10 +218,6 @@ CheckpointerMain(void)
 	 * Reset some signals that are accepted by postmaster but not here
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	/* We allow SIGQUIT (quickdie) at all times */
 	sigdelset(&BlockSig, SIGQUIT);
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 885e85ad8af..0ebd63650c6 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -226,11 +226,8 @@ PgArchiverMain(int argc, char *argv[])
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, pgarch_waken);
 	pqsignal(SIGUSR2, pgarch_waken_stop);
+	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 	PG_SETMASK(&UnBlockSig);
 
 	/*
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 42bccce0af4..790d7f02af1 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -4267,11 +4267,8 @@ PgstatCollectorMain(int argc, char *argv[])
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, SIG_IGN);
 	pqsignal(SIGUSR2, SIG_IGN);
+	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 	PG_SETMASK(&UnBlockSig);
 
 	/*
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index cb49f3255f9..68bb35ab791 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -646,8 +646,17 @@ PostmasterMain(int argc, char *argv[])
 	pqsignal_no_restart(SIGUSR2, dummy_handler);	/* unused, reserve for
 													 * children */
 	pqsignal_no_restart(SIGCHLD, reaper);	/* handle child termination */
+
+	/*
+	 * No other place in Postgres should touch SIGTTIN/SIGTTOU handling.  We
+	 * ignore those signals in a postmaster environment, so that there is no
+	 * risk of a child process freezing up due to writing to stderr.  But for
+	 * a standalone backend, their default handling is reasonable.  Hence, all
+	 * child processes should just allow the inherited settings to stand.
+	 */
 	pqsignal(SIGTTIN, SIG_IGN); /* ignored */
 	pqsignal(SIGTTOU, SIG_IGN); /* ignored */
+
 	/* ignore SIGXFSZ, so that ulimit violations work like disk full */
 #ifdef SIGXFSZ
 	pqsignal(SIGXFSZ, SIG_IGN); /* ignored */
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index 2926211e35d..983a05d7db5 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -188,10 +188,6 @@ StartupProcessMain(void)
 	 * Reset some signals that are accepted by postmaster but not here
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	/*
 	 * Register timeouts needed for standby mode
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 29bdcec8958..35755138890 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -257,10 +257,6 @@ SysLoggerMain(int argc, char *argv[])
 	 * Reset some signals that are accepted by postmaster but not here
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	PG_SETMASK(&UnBlockSig);
 
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index fb66bceeedf..3e09827854d 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -121,10 +121,6 @@ WalWriterMain(void)
 	 * Reset some signals that are accepted by postmaster but not here
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	/* We allow SIGQUIT (quickdie) at all times */
 	sigdelset(&BlockSig, SIGQUIT);
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 6f4b3538ac4..cb7bb47c9bd 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -279,10 +279,6 @@ WalReceiverMain(void)
 
 	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 
 	/* We allow SIGQUIT (quickdie) at all times */
 	sigdelset(&BlockSig, SIGQUIT);
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 39337d2f1f8..3f24f9b4e05 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3003,10 +3003,6 @@ WalSndSignals(void)
 
 	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
-	pqsignal(SIGTTIN, SIG_DFL);
-	pqsignal(SIGTTOU, SIG_DFL);
-	pqsignal(SIGCONT, SIG_DFL);
-	pqsignal(SIGWINCH, SIG_DFL);
 }
 
 /* Report shared-memory space needed by WalSndShmemInit */