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process-util: add FORK_DETACH flag for forking of detached child

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A test for this is later added indirectly, via aynchronous_rm_rf() that
uses this and comes with a suitable test.
This commit is contained in:
Lennart Poettering
2023-06-23 10:02:15 +02:00
parent f7bccef178
commit 2e7b105eb9
2 changed files with 35 additions and 2 deletions
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src/basic/process-util.c
+34 -2
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@@ -1195,9 +1195,12 @@ int safe_fork_full(
pid_t original_pid, pid;
sigset_t saved_ss, ss;
_unused_ _cleanup_(restore_sigsetp) sigset_t *saved_ssp = NULL;
bool block_signals = false, block_all = false;
bool block_signals = false, block_all = false, intermediary = false;
int prio, r;
assert(!FLAGS_SET(flags, FORK_DETACH) || !ret_pid);
assert(!FLAGS_SET(flags, FORK_DETACH|FORK_WAIT));
/* A wrapper around fork(), that does a couple of important initializations in addition to mere forking. Always
* returns the child's PID in *ret_pid. Returns == 0 in the child, and > 0 in the parent. */
@@ -1231,6 +1234,31 @@ int safe_fork_full(
saved_ssp = &saved_ss;
}
if (FLAGS_SET(flags, FORK_DETACH)) {
assert(!FLAGS_SET(flags, FORK_WAIT));
assert(!ret_pid);
/* Fork off intermediary child if needed */
r = is_reaper_process();
if (r < 0)
return log_full_errno(prio, r, "Failed to determine if we are a reaper process: %m");
if (!r) {
/* Not a reaper process, hence do a double fork() so we are reparented to one */
pid = fork();
if (pid < 0)
return log_full_errno(prio, errno, "Failed to fork off '%s': %m", strna(name));
if (pid > 0) {
log_debug("Successfully forked off intermediary '%s' as PID " PID_FMT ".", strna(name), pid);
return 1; /* return in the parent */
}
intermediary = true;
}
}
if ((flags & (FORK_NEW_MOUNTNS|FORK_NEW_USERNS)) != 0)
pid = raw_clone(SIGCHLD|
(FLAGS_SET(flags, FORK_NEW_MOUNTNS) ? CLONE_NEWNS : 0) |
@@ -1240,8 +1268,12 @@ int safe_fork_full(
if (pid < 0)
return log_full_errno(prio, errno, "Failed to fork off '%s': %m", strna(name));
if (pid > 0) {
/* We are in the parent process */
/* If we are in the intermediary process, exit now */
if (intermediary)
_exit(EXIT_SUCCESS);
/* We are in the parent process */
log_debug("Successfully forked off '%s' as PID " PID_FMT ".", strna(name), pid);
if (flags & FORK_WAIT) {