0006-Pass-CAC-as-argument-to-backend-process.patch

From c25b67c045018a2bf05e6ff53819d26e561fc83f Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Sun, 18 Jun 2023 14:11:16 +0300
Subject: [PATCH 6/9] Pass CAC as argument to backend process.

We used to smuggle it to the child process in the Port struct, but it seems
better to pass it down as a separate argument.
---
 src/backend/postmaster/postmaster.c | 43 +++++++++++++++++++++--------
 src/include/libpq/libpq-be.h        | 12 --------
 2 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index fa6f2c8e29c..3ce9d76a850 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -417,7 +417,18 @@ static void HandleChildCrash(int pid, int exitstatus, const char *procname);
 static void LogChildExit(int lev, const char *procname,
 						 int pid, int exitstatus);
 static void PostmasterStateMachine(void);
-static void BackendInitialize(Port *port);
+
+typedef enum CAC_state
+{
+	CAC_OK,
+	CAC_STARTUP,
+	CAC_SHUTDOWN,
+	CAC_RECOVERY,
+	CAC_NOTCONSISTENT,
+	CAC_TOOMANY
+} CAC_state;
+
+static void BackendInitialize(Port *port, CAC_state cac);
 static void BackendRun(Port *port) pg_attribute_noreturn();
 static void ExitPostmaster(int status) pg_attribute_noreturn();
 static int	ServerLoop(void);
@@ -474,7 +485,7 @@ typedef struct
 } win32_deadchild_waitinfo;
 #endif							/* WIN32 */
 
-static pid_t backend_forkexec(Port *port);
+static pid_t backend_forkexec(Port *port, CAC_state cac);
 static pid_t internal_forkexec(int argc, char *argv[], Port *port);
 
 /* Type for a socket that can be inherited to a client process */
@@ -4075,6 +4086,7 @@ BackendStartup(Port *port)
 {
 	Backend    *bn;				/* for backend cleanup */
 	pid_t		pid;
+	CAC_state	cac;
 
 	/*
 	 * Create backend data structure.  Better before the fork() so we can
@@ -4106,8 +4118,8 @@ BackendStartup(Port *port)
 	bn->cancel_key = MyCancelKey;
 
 	/* Pass down canAcceptConnections state */
-	port->canAcceptConnections = canAcceptConnections(BACKEND_TYPE_NORMAL);
-	bn->dead_end = (port->canAcceptConnections != CAC_OK);
+	cac = canAcceptConnections(BACKEND_TYPE_NORMAL);
+	bn->dead_end = (cac != CAC_OK);
 
 	/*
 	 * Unless it's a dead_end child, assign it a child slot number
@@ -4121,7 +4133,7 @@ BackendStartup(Port *port)
 	bn->bgworker_notify = false;
 
 #ifdef EXEC_BACKEND
-	pid = backend_forkexec(port);
+	pid = backend_forkexec(port, cac);
 #else							/* !EXEC_BACKEND */
 	pid = fork_process();
 	if (pid == 0)				/* child */
@@ -4133,7 +4145,7 @@ BackendStartup(Port *port)
 		ClosePostmasterPorts(false);
 
 		/* Perform additional initialization and collect startup packet */
-		BackendInitialize(port);
+		BackendInitialize(port, cac);
 
 		/* And run the backend */
 		BackendRun(port);
@@ -4220,7 +4232,7 @@ report_fork_failure_to_client(Port *port, int errnum)
  * but have not yet set up most of our local pointers to shmem structures.
  */
 static void
-BackendInitialize(Port *port)
+BackendInitialize(Port *port, CAC_state cac)
 {
 	int			status;
 	int			ret;
@@ -4353,7 +4365,7 @@ BackendInitialize(Port *port)
 	 * now instead of wasting cycles on an authentication exchange. (This also
 	 * allows a pg_ping utility to be written.)
 	 */
-	switch (port->canAcceptConnections)
+	switch (cac)
 	{
 		case CAC_STARTUP:
 			ereport(FATAL,
@@ -4498,15 +4510,19 @@ postmaster_forkexec(int argc, char *argv[])
  * returns the pid of the fork/exec'd process, or -1 on failure
  */
 static pid_t
-backend_forkexec(Port *port)
+backend_forkexec(Port *port, CAC_state cac)
 {
-	char	   *av[4];
+	char	   *av[5];
 	int			ac = 0;
+	char		cacbuf[10];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forkbackend";
 	av[ac++] = NULL;			/* filled in by internal_forkexec */
 
+	snprintf(cacbuf, sizeof(cacbuf), "%d", (int) cac);
+	av[ac++] = cacbuf;
+
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
 
@@ -4910,7 +4926,10 @@ SubPostmasterMain(int argc, char *argv[])
 	/* Run backend or appropriate child */
 	if (strcmp(argv[1], "--forkbackend") == 0)
 	{
-		Assert(argc == 3);		/* shouldn't be any more args */
+		CAC_state	cac;
+
+		Assert(argc == 4);
+		cac = (CAC_state) atoi(argv[3]);
 
 		/*
 		 * Need to reinitialize the SSL library in the backend, since the
@@ -4944,7 +4963,7 @@ SubPostmasterMain(int argc, char *argv[])
 		 * PGPROC slots, we have already initialized libpq and are able to
 		 * report the error to the client.
 		 */
-		BackendInitialize(&port);
+		BackendInitialize(&port, cac);
 
 		/* Restore basic shared memory pointers */
 		InitShmemAccess(UsedShmemSegAddr);
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 3b2ce9908f8..625caa853a0 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -58,17 +58,6 @@ typedef struct
 #include "libpq/pqcomm.h"
 
 
-typedef enum CAC_state
-{
-	CAC_OK,
-	CAC_STARTUP,
-	CAC_SHUTDOWN,
-	CAC_RECOVERY,
-	CAC_NOTCONSISTENT,
-	CAC_TOOMANY
-} CAC_state;
-
-
 /*
  * GSSAPI specific state information
  */
@@ -156,7 +145,6 @@ typedef struct Port
 	int			remote_hostname_resolv; /* see above */
 	int			remote_hostname_errcode;	/* see above */
 	char	   *remote_port;	/* text rep of remote port */
-	CAC_state	canAcceptConnections;	/* postmaster connection status */
 
 	/*
 	 * Information that needs to be saved from the startup packet and passed
-- 
2.30.2