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mon_tools: Improve systemctl start error handling

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This fixes the same issue as in commit 82c8148983 ("cpuplugd: Improve
systemctl start error handling") for mon_tools (mon_procd and mon_fsstatd).

Currently "systemctl start mon_procd/fsstatd" does not report any errors
in case the startup fails.

Example (with mon_procd):

 (change interval in /etc/sysconfig/mon_procd to an invalid value "abc")
 # systemctl start mon_procd

The reason is that for type=simple systemd forks/execs mon_procd and if
that is successful immediately returns. There is no way to find out if the
initial startup fails.

Fix this by using type=fork and running the process in the background. In
this case systemd waits until the initial process returns.

In addition use PIDFile and ensure that the pid file is already available
when the initial process returns. To achieve this, use startup
synchronization via pipe. Without that systemd would print the following
warning:

systemd[1]: mon_procd.service: PID file /var/run/mon_procd.pid not readable
            (yet?) after start: No such file or directory

With this patch, an early startup error like in the example above, is now
reported correctly in "systemctl start":

 # systemctl start mon_procd
   Job for mon_procd.service failed because the control process exited...
   See "systemctl status mon_procd.service" and "journalctl -xe" for ...
 # journalctl -xe | grep mon_procd
   mon_procd[3184]: Error: Invalid interval (needs to be greater than 0)

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
This commit is contained in:
Gerald Schaefer
2017-11-20 18:21:29 +01:00
committed by Michael Holzheu
parent 82c8148983
commit 780133f825
4 changed files with 70 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mon_tools/mon_fsstatd.c
+32 -8
View File
@@ -90,17 +90,18 @@ static void fsstatd_open_monwriter(void)
/*
* Store daemon's pid so it can be stopped
*/
static void store_pid(void)
static int store_pid(void)
{
FILE *f = fopen(pid_file, "w");
if (!f) {
syslog(LOG_ERR, "cannot open pid file %s: %s", pid_file,
strerror(errno));
exit(1);
return -1;
}
fprintf(f, "%d\n", getpid());
fclose(f);
return 0;
}
/*
@@ -244,41 +245,64 @@ static void fsstatd_write_ent(struct mntent *ent, time_t curr_time,
*/
static void fsstatd_daemonize(void)
{
int pipe_fds[2], startup_rc = 1;
pid_t pid;
if (pipe(pipe_fds) == -1) {
syslog(LOG_ERR, "pipe error: %s\n", strerror(errno));
exit(1);
}
/* Fork off the parent process */
pid = fork();
if (pid < 0) {
syslog(LOG_ERR, "fork error: %s\n", strerror(errno));
exit(1);
}
if (pid > 0)
exit(0);
if (pid > 0) {
/* Wait for startup return code from daemon */
if (read(pipe_fds[0], &startup_rc, sizeof(startup_rc)) == -1)
syslog(LOG_ERR, "pipe read error: %s\n", strerror(errno));
/* With startup_rc == 0, pid file was written at this point */
exit(startup_rc);
}
/* Change the file mode mask */
umask(0);
/* Store daemon pid */
store_pid();
/* Catch SIGINT and SIGTERM to clean up pid file on exit */
fsstatd_handle_signals();
/* Create a new SID for the child process */
if (setsid() < 0) {
syslog(LOG_ERR, "setsid error: %s\n", strerror(errno));
exit(1);
goto notify_parent;
}
/* Change the current working directory */
if (chdir("/") < 0) {
syslog(LOG_ERR, "chdir error: %s\n", strerror(errno));
exit(1);
goto notify_parent;
}
/* Close out the standard file descriptors */
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
/* Store daemon pid */
if (store_pid() < 0)
goto notify_parent;
startup_rc = 0;
notify_parent:
/* Inform waiting parent about startup return code */
if (write(pipe_fds[1], &startup_rc, sizeof(startup_rc)) == -1) {
syslog(LOG_ERR, "pipe write error: %s\n", strerror(errno));
exit(1);
}
if (startup_rc != 0)
exit(startup_rc);
}
static int fsstatd_do_work(void)
mon_tools/mon_procd.c
+32 -8
View File
@@ -109,17 +109,18 @@ static void procd_open_monwriter(void)
/*
* Store daemon's pid so it can be stopped
*/
static void store_pid(void)
static int store_pid(void)
{
FILE *f = fopen(pid_file, "w");
if (!f) {
syslog(LOG_ERR, "cannot open pid file %s: %s", pid_file,
strerror(errno));
exit(1);
return -1;
}
fprintf(f, "%d\n", getpid());
fclose(f);
return 0;
}
/*
@@ -897,41 +898,64 @@ static void read_tasks(void)
*/
static void procd_daemonize(void)
{
int pipe_fds[2], startup_rc = 1;
pid_t pid;
if (pipe(pipe_fds) == -1) {
syslog(LOG_ERR, "pipe error: %s\n", strerror(errno));
exit(1);
}
/* Fork off the parent process */
pid = fork();
if (pid < 0) {
syslog(LOG_ERR, "fork error: %s\n", strerror(errno));
exit(1);
}
if (pid > 0)
exit(0);
if (pid > 0) {
/* Wait for startup return code from daemon */
if (read(pipe_fds[0], &startup_rc, sizeof(startup_rc)) == -1)
syslog(LOG_ERR, "pipe read error: %s\n", strerror(errno));
/* With startup_rc == 0, pid file was written at this point */
exit(startup_rc);
}
/* Change the file mode mask */
umask(0);
/* Store daemon pid */
store_pid();
/* Catch SIGINT and SIGTERM to clean up pid file on exit */
procd_handle_signals();
/* Create a new SID for the child process */
if (setsid() < 0) {
syslog(LOG_ERR, "setsid error: %s\n", strerror(errno));
exit(1);
goto notify_parent;
}
/* Change the current working directory */
if (chdir("/") < 0) {
syslog(LOG_ERR, "chdir error: %s\n", strerror(errno));
exit(1);
goto notify_parent;
}
/* Close out the standard file descriptors */
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
/* Store daemon pid */
if (store_pid() < 0)
goto notify_parent;
startup_rc = 0;
notify_parent:
/* Inform waiting parent about startup return code */
if (write(pipe_fds[1], &startup_rc, sizeof(startup_rc)) == -1) {
syslog(LOG_ERR, "pipe write error: %s\n", strerror(errno));
exit(1);
}
if (startup_rc != 0)
exit(startup_rc);
}
static int procd_do_work(void)
systemd/mon_fsstatd.service.in
+3 -2
View File
@@ -30,10 +30,11 @@ EnvironmentFile=@sysconf_path@/sysconfig/mon_fsstatd
ExecStartPre=-/sbin/modprobe monwriter
ExecStartPre=/sbin/udevadm settle --timeout=10
ExecStart=@usrsbin_path@/mon_fsstatd -a -i $FSSTAT_INTERVAL
ExecStart=@usrsbin_path@/mon_fsstatd -i $FSSTAT_INTERVAL
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Type=simple
Type=forking
PIDFile=/var/run/mon_fsstatd.pid
[Install]
WantedBy=multi-user.target
systemd/mon_procd.service.in
+3 -2
View File
@@ -30,10 +30,11 @@ EnvironmentFile=@sysconf_path@/sysconfig/mon_procd
ExecStartPre=-/sbin/modprobe monwriter
ExecStartPre=/sbin/udevadm settle --timeout=10
ExecStart=@usrsbin_path@/mon_procd -a -i $PROC_INTERVAL
ExecStart=@usrsbin_path@/mon_procd -i $PROC_INTERVAL
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Type=simple
Type=forking
PIDFile=/var/run/mon_procd.pid
[Install]
WantedBy=multi-user.target