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Neil Conway
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Refactor fork()-related code. We need to do various housekeeping tasks
before we can invoke fork() -- flush stdio buffers, save and restore the profiling timer on Linux with LINUX_PROFILE, and handle BeOS stuff. This patch moves that code into a single function, fork_process(), instead of duplicating it at the various callsites of fork(). This patch doesn't address the EXEC_BACKEND case; there is room for further cleanup there.
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7 files changed

+108
-151
lines changed

7 files changed

+108
-151
lines changed

‎src/backend/port/beos/support.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -265,7 +265,7 @@ beos_startup(int argc, char **argv)
265265

266266

267267

268-
/* The behavior of fork is borken on beos regarding shared memory. In fact
268+
/* The behavior of fork is broken on beos regarding shared memory. In fact
269269
all shared memory areas are clones in copy on write mode in the new process.
270270
271271
We need to do a remapping of these areas. Just afer the fork we performe the

‎src/backend/postmaster/Makefile

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4,15 +4,15 @@
44
# Makefile for src/backend/postmaster
55
#
66
# IDENTIFICATION
7-
# $PostgreSQL: pgsql/src/backend/postmaster/Makefile,v 1.19 2004/08/05 23:32:10 tgl Exp $
7+
# $PostgreSQL: pgsql/src/backend/postmaster/Makefile,v 1.20 2005/03/10 07:14:03 neilc Exp $
88
#
99
#-------------------------------------------------------------------------
1010

1111
subdir = src/backend/postmaster
1212
top_builddir = ../../..
1313
include $(top_builddir)/src/Makefile.global
1414

15-
OBJS = postmaster.o bgwriter.o pgstat.o pgarch.o syslogger.o
15+
OBJS = bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o syslogger.o
1616

1717
all: SUBSYS.o
1818

‎src/backend/postmaster/fork_process.c

Lines changed: 80 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,80 @@
1+
/*
2+
* fork_process.c
3+
* A simple wrapper on top of fork(). This does not handle the
4+
* EXEC_BACKEND case; it might be extended to do so, but it would be
5+
* considerably more complex.
6+
*
7+
* Copyright (c) 1996-2005, PostgreSQL Global Development Group
8+
*
9+
* IDENTIFICATION
10+
* $PostgreSQL: pgsql/src/backend/postmaster/fork_process.c,v 1.1 2005/03/10 07:14:03 neilc Exp $
11+
*/
12+
#include "postgres.h"
13+
#include "postmaster/fork_process.h"
14+
15+
#include <unistd.h>
16+
17+
/*
18+
* Wrapper for fork(). Return values are the same as those for fork():
19+
* -1 if the fork failed, 0 in the child process, and the PID of the
20+
* child in the parent process.
21+
*/
22+
pid_t
23+
fork_process(void)
24+
{
25+
pid_t result;
26+
#ifdef LINUX_PROFILE
27+
struct itimerval prof_itimer;
28+
#endif
29+
30+
/*
31+
* Flush stdio channels just before fork, to avoid double-output
32+
* problems. Ideally we'd use fflush(NULL) here, but there are still a
33+
* few non-ANSI stdio libraries out there (like SunOS 4.1.x) that
34+
* coredump if we do. Presently stdout and stderr are the only stdio
35+
* output channels used by the postmaster, so fflush'ing them should
36+
* be sufficient.
37+
*/
38+
fflush(stdout);
39+
fflush(stderr);
40+
41+
#ifdef LINUX_PROFILE
42+
/*
43+
* Linux's fork() resets the profiling timer in the child process. If
44+
* we want to profile child processes then we need to save and restore
45+
* the timer setting. This is a waste of time if not profiling,
46+
* however, so only do it if commanded by specific -DLINUX_PROFILE
47+
* switch.
48+
*/
49+
getitimer(ITIMER_PROF, &prof_itimer);
50+
#endif
51+
52+
#ifdef __BEOS__
53+
/* Specific beos actions before backend startup */
54+
beos_before_backend_startup();
55+
#endif
56+
57+
result = fork();
58+
if (result == (pid_t) -1)
59+
{
60+
/* fork failed */
61+
#ifdef __BEOS__
62+
/* Specific beos backend startup actions */
63+
beos_backend_startup_failed();
64+
#endif
65+
}
66+
else if (result == 0)
67+
{
68+
/* fork succeeded, in child */
69+
#ifdef LINUX_PROFILE
70+
setitimer(ITIMER_PROF, &prof_itimer, NULL);
71+
#endif
72+
73+
#ifdef __BEOS__
74+
/* Specific beos backend startup actions */
75+
beos_backend_startup();
76+
#endif
77+
}
78+
79+
return result;
80+
}

‎src/backend/postmaster/pgarch.c

Lines changed: 3 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@
1919
*
2020
*
2121
* IDENTIFICATION
22-
* $PostgreSQL: pgsql/src/backend/postmaster/pgarch.c,v 1.14 2004/12/31 22:00:40 pgsql Exp $
22+
* $PostgreSQL: pgsql/src/backend/postmaster/pgarch.c,v 1.15 2005/03/10 07:14:03 neilc Exp $
2323
*
2424
*-------------------------------------------------------------------------
2525
*/
@@ -34,6 +34,7 @@
3434
#include "access/xlog_internal.h"
3535
#include "libpq/pqsignal.h"
3636
#include "miscadmin.h"
37+
#include "postmaster/fork_process.h"
3738
#include "postmaster/pgarch.h"
3839
#include "postmaster/postmaster.h"
3940
#include "storage/fd.h"
@@ -141,36 +142,20 @@ pgarch_start(void)
141142
return 0;
142143
last_pgarch_start_time = curtime;
143144

144-
fflush(stdout);
145-
fflush(stderr);
146-
147-
#ifdef __BEOS__
148-
/* Specific beos actions before backend startup */
149-
beos_before_backend_startup();
150-
#endif
151-
152145
#ifdef EXEC_BACKEND
153146
switch ((pgArchPid = pgarch_forkexec()))
154147
#else
155-
switch ((pgArchPid = fork()))
148+
switch ((pgArchPid = fork_process()))
156149
#endif
157150
{
158151
case -1:
159-
#ifdef __BEOS__
160-
/* Specific beos actions */
161-
beos_backend_startup_failed();
162-
#endif
163152
ereport(LOG,
164153
(errmsg("could not fork archiver: %m")));
165154
return 0;
166155

167156
#ifndef EXEC_BACKEND
168157
case 0:
169158
/* in postmaster child ... */
170-
#ifdef __BEOS__
171-
/* Specific beos actions after backend startup */
172-
beos_backend_startup();
173-
#endif
174159
/* Close the postmaster's sockets */
175160
ClosePostmasterPorts(false);
176161

‎src/backend/postmaster/postmaster.c

Lines changed: 11 additions & 109 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
3737
*
3838
*
3939
* IDENTIFICATION
40-
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.445 2005/02/22 04:36:36 momjian Exp $
40+
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.446 2005/03/10 07:14:03 neilc Exp $
4141
*
4242
* NOTES
4343
*
@@ -92,6 +92,8 @@
9292
#include <DNSServiceDiscovery/DNSServiceDiscovery.h>
9393
#endif
9494

95+
#include "access/xlog.h"
96+
#include "bootstrap/bootstrap.h"
9597
#include "catalog/pg_control.h"
9698
#include "catalog/pg_database.h"
9799
#include "commands/async.h"
@@ -103,23 +105,22 @@
103105
#include "libpq/pqsignal.h"
104106
#include "miscadmin.h"
105107
#include "nodes/nodes.h"
106-
#include "postmaster/postmaster.h"
108+
#include "pgstat.h"
109+
#include "postmaster/fork_process.h"
107110
#include "postmaster/pgarch.h"
111+
#include "postmaster/postmaster.h"
108112
#include "postmaster/syslogger.h"
113+
#include "storage/bufmgr.h"
109114
#include "storage/fd.h"
110115
#include "storage/ipc.h"
111116
#include "storage/pg_shmem.h"
112117
#include "storage/pmsignal.h"
113118
#include "storage/proc.h"
114-
#include "storage/bufmgr.h"
115-
#include "access/xlog.h"
116119
#include "tcop/tcopprot.h"
117120
#include "utils/builtins.h"
118121
#include "utils/guc.h"
119122
#include "utils/memutils.h"
120123
#include "utils/ps_status.h"
121-
#include "bootstrap/bootstrap.h"
122-
#include "pgstat.h"
123124

124125
#ifdef EXEC_BACKEND
125126
#include "storage/spin.h"
@@ -1008,16 +1009,7 @@ pmdaemonize(void)
10081009
int i;
10091010
pid_t pid;
10101011

1011-
#ifdef LINUX_PROFILE
1012-
struct itimerval prof_itimer;
1013-
#endif
1014-
1015-
#ifdef LINUX_PROFILE
1016-
/* see comments in BackendStartup */
1017-
getitimer(ITIMER_PROF, &prof_itimer);
1018-
#endif
1019-
1020-
pid = fork();
1012+
pid = fork_process();
10211013
if (pid == (pid_t) -1)
10221014
{
10231015
write_stderr("%s: could not fork background process: %s\n",
@@ -1030,10 +1022,6 @@ pmdaemonize(void)
10301022
_exit(0);
10311023
}
10321024

1033-
#ifdef LINUX_PROFILE
1034-
setitimer(ITIMER_PROF, &prof_itimer, NULL);
1035-
#endif
1036-
10371025
MyProcPid = PostmasterPid = getpid(); /* reset PID vars to child */
10381026

10391027
/* GH: If there's no setsid(), we hopefully don't need silent mode.
@@ -2382,10 +2370,6 @@ BackendStartup(Port *port)
23822370
Backend *bn; /* for backend cleanup */
23832371
pid_t pid;
23842372

2385-
#ifdef LINUX_PROFILE
2386-
struct itimerval prof_itimer;
2387-
#endif
2388-
23892373
/*
23902374
* Compute the cancel key that will be assigned to this backend. The
23912375
* backend will have its own copy in the forked-off process' value of
@@ -2409,54 +2393,13 @@ BackendStartup(Port *port)
24092393
/* Pass down canAcceptConnections state (kluge for EXEC_BACKEND case) */
24102394
port->canAcceptConnections = canAcceptConnections();
24112395

2412-
/*
2413-
* Flush stdio channels just before fork, to avoid double-output
2414-
* problems. Ideally we'd use fflush(NULL) here, but there are still a
2415-
* few non-ANSI stdio libraries out there (like SunOS 4.1.x) that
2416-
* coredump if we do. Presently stdout and stderr are the only stdio
2417-
* output channels used by the postmaster, so fflush'ing them should
2418-
* be sufficient.
2419-
*/
2420-
fflush(stdout);
2421-
fflush(stderr);
2422-
24232396
#ifdef EXEC_BACKEND
2424-
24252397
pid = backend_forkexec(port);
2426-
24272398
#else /* !EXEC_BACKEND */
2428-
2429-
#ifdef LINUX_PROFILE
2430-
2431-
/*
2432-
* Linux's fork() resets the profiling timer in the child process. If
2433-
* we want to profile child processes then we need to save and restore
2434-
* the timer setting. This is a waste of time if not profiling,
2435-
* however, so only do it if commanded by specific -DLINUX_PROFILE
2436-
* switch.
2437-
*/
2438-
getitimer(ITIMER_PROF, &prof_itimer);
2439-
#endif
2440-
2441-
#ifdef __BEOS__
2442-
/* Specific beos actions before backend startup */
2443-
beos_before_backend_startup();
2444-
#endif
2445-
2446-
pid = fork();
2447-
2399+
pid = fork_process();
24482400
if (pid == 0) /* child */
24492401
{
2450-
#ifdef LINUX_PROFILE
2451-
setitimer(ITIMER_PROF, &prof_itimer, NULL);
2452-
#endif
2453-
2454-
#ifdef __BEOS__
2455-
/* Specific beos backend startup actions */
2456-
beos_backend_startup();
2457-
#endif
24582402
free(bn);
2459-
24602403
proc_exit(BackendRun(port));
24612404
}
24622405
#endif /* EXEC_BACKEND */
@@ -2466,10 +2409,6 @@ BackendStartup(Port *port)
24662409
/* in parent, fork failed */
24672410
int save_errno = errno;
24682411

2469-
#ifdef __BEOS__
2470-
/* Specific beos backend startup actions */
2471-
beos_backend_startup_failed();
2472-
#endif
24732412
free(bn);
24742413
errno = save_errno;
24752414
ereport(LOG,
@@ -2945,7 +2884,7 @@ internal_forkexec(int argc, char *argv[], Port *port)
29452884
argv[2] = tmpfilename;
29462885

29472886
/* Fire off execv in child */
2948-
if ((pid = fork()) == 0)
2887+
if ((pid = fork_process()) == 0)
29492888
{
29502889
if (execv(postgres_exec_path, argv) < 0)
29512890
{
@@ -3465,10 +3404,6 @@ StartChildProcess(int xlop)
34653404
int ac = 0;
34663405
char xlbuf[32];
34673406

3468-
#ifdef LINUX_PROFILE
3469-
struct itimerval prof_itimer;
3470-
#endif
3471-
34723407
/*
34733408
* Set up command-line arguments for subprocess
34743409
*/
@@ -3488,41 +3423,13 @@ StartChildProcess(int xlop)
34883423
av[ac] = NULL;
34893424
Assert(ac < lengthof(av));
34903425

3491-
/*
3492-
* Flush stdio channels (see comments in BackendStartup)
3493-
*/
3494-
fflush(stdout);
3495-
fflush(stderr);
3496-
34973426
#ifdef EXEC_BACKEND
3498-
34993427
pid = postmaster_forkexec(ac, av);
3500-
35013428
#else /* !EXEC_BACKEND */
3502-
3503-
#ifdef LINUX_PROFILE
3504-
/* see comments in BackendStartup */
3505-
getitimer(ITIMER_PROF, &prof_itimer);
3506-
#endif
3507-
3508-
#ifdef __BEOS__
3509-
/* Specific beos actions before backend startup */
3510-
beos_before_backend_startup();
3511-
#endif
3512-
3513-
pid = fork();
3429+
pid = fork_process();
35143430

35153431
if (pid == 0) /* child */
35163432
{
3517-
#ifdef LINUX_PROFILE
3518-
setitimer(ITIMER_PROF, &prof_itimer, NULL);
3519-
#endif
3520-
3521-
#ifdef __BEOS__
3522-
/* Specific beos actions after backend startup */
3523-
beos_backend_startup();
3524-
#endif
3525-
35263433
IsUnderPostmaster = true; /* we are a postmaster subprocess
35273434
* now */
35283435

@@ -3546,11 +3453,6 @@ StartChildProcess(int xlop)
35463453
{
35473454
/* in parent, fork failed */
35483455
int save_errno = errno;
3549-
3550-
#ifdef __BEOS__
3551-
/* Specific beos actions before backend startup */
3552-
beos_backend_startup_failed();
3553-
#endif
35543456
errno = save_errno;
35553457
switch (xlop)
35563458
{

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