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cpacfstatsd: use a PIPE to notify the parent that the initialization is done

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Use a PIPE to notify the parent that the initialization is complete and
all external communication channels are established. See
https://www.freedesktop.org/software/systemd/man/daemon.html for
details.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Marc Hartmayer
2023-05-26 11:13:06 +00:00
committed by Jan Höppner
parent 10f8565e32
commit 94e0b644a7
1 changed files with 50 additions and 10 deletions
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60
cpacfstats/cpacfstatsd.c
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@@ -252,14 +252,20 @@ static int do_print(int s, enum ctr_e ctr)
}
static int become_daemon(void)
static int become_daemon(int *startup_pipe)
{
int child_initialized = 0, fd;
int pipefds[2];
FILE *f;
int fd;
/* syslog */
openlog("cpacfstatsd", 0, LOG_DAEMON);
if (pipe(pipefds) != 0) {
eprint("pipe() failed, errno=%d [%s]\n", errno, strerror(errno));
return -1;
}
/*
* fork and terminate parent
* Reasons:
@@ -276,9 +282,23 @@ static int become_daemon(void)
case 0: /* child */
break;
default: /* parent */
(void)close(pipefds[1]);
if (read(pipefds[0], &child_initialized, sizeof(child_initialized)) !=
sizeof(child_initialized)) {
eprint("Couldn't read from PIPE, errno=%d [%s]\n", errno, strerror(errno));
(void)close(pipefds[0]);
_exit(EXIT_FAILURE);
}
(void)close(pipefds[0]);
if (!child_initialized)
_exit(EXIT_FAILURE);
_exit(0);
}
/* Executed within the child context only */
(void)close(pipefds[0]);
*startup_pipe = pipefds[1];
if (chdir("/") != 0) {
eprint("Chdir('/') failed, errno=%d [%s]\n",
errno, strerror(errno));
@@ -418,7 +438,7 @@ int eprint(const char *format, ...)
int main(int argc, char *argv[])
{
int rc, sfd, foreground = 0;
int rc, sfd, foreground = 0, startup_pipe = -1, initialized = 0;
struct sigaction act;
if (argc > 1) {
@@ -459,22 +479,22 @@ int main(int argc, char *argv[])
}
if (!foreground) {
if (become_daemon() != 0) {
if (become_daemon(&startup_pipe) != 0) {
eprint("Couldn't daemonize\n");
return EXIT_FAILURE;
goto error;
}
}
if (perf_init() != 0) {
eprint("Couldn't initialize perf lib\n");
return EXIT_FAILURE;
goto error;
}
atexit(perf_close);
sfd = open_socket(SERVER);
if (sfd < 0) {
eprint("Couldn't initialize server socket\n");
return EXIT_FAILURE;
goto error;
}
atexit(remove_sock);
@@ -484,17 +504,27 @@ int main(int argc, char *argv[])
if (sigaction(SIGINT, &act, 0) != 0) {
eprint("Couldn't establish signal handler for SIGINT, errno=%d [%s]\n",
errno, strerror(errno));
return EXIT_FAILURE;
goto error;
}
if (sigaction(SIGTERM, &act, 0) != 0) {
eprint("Couldn't establish signal handler for SIGTERM, errno=%d [%s]\n",
errno, strerror(errno));
return EXIT_FAILURE;
goto error;
}
/* Ignore SIGPIPE such that we see EPIPE as return from write. */
signal(SIGPIPE, SIG_IGN);
eprint("Running\n");
initialized = 1;
/* `startup_pipe` has been initialized, so we know we are
* running in daemon mode. Let's write to the pipe so that the
* parent knows that the initialization is complete.
*/
if (startup_pipe != -1 &&
write(startup_pipe, &initialized, sizeof(initialized)) != sizeof(initialized))
goto error;
(void)close(startup_pipe);
startup_pipe = -1;
while (!stopsig) {
enum ctr_e ctr;
@@ -507,7 +537,7 @@ int main(int argc, char *argv[])
continue;
eprint("Accept() failure, errno=%d [%s]\n",
errno, strerror(errno));
return EXIT_FAILURE;
goto error;
}
rc = recv_query(s, &ctr, &cmd);
@@ -542,4 +572,14 @@ int main(int argc, char *argv[])
remove_pidfile();
return 0;
error:
if (startup_pipe != -1) {
/* Notify the parent process that there was an error */
if (write(startup_pipe, &initialized, sizeof(initialized)) != sizeof(initialized))
eprint("Couldn't write to PIPE, errno=%d [%s]\n", errno, strerror(errno));
(void)close(startup_pipe);
}
return EXIT_FAILURE;
}