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process-util: add new helper pidref_get_ppid_as_pidref()

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This commit is contained in:
Lennart Poettering 2025-01-07 09:53:53 +01:00
parent 8c0da3af28
commit 9237a63a80
3 changed files with 62 additions and 0 deletions
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38
src/basic/process-util.c
View File

@ -742,6 +742,44 @@ int pidref_get_ppid(const PidRef *pidref, pid_t *ret) {
return 0;
}
int pidref_get_ppid_as_pidref(const PidRef *pidref, PidRef *ret) {
pid_t ppid;
int r;
assert(ret);
r = pidref_get_ppid(pidref, &ppid);
if (r < 0)
return r;
for (unsigned attempt = 0; attempt < 16; attempt++) {
_cleanup_(pidref_done) PidRef parent = PIDREF_NULL;
r = pidref_set_pid(&parent, ppid);
if (r < 0)
return r;
/* If we have a pidfd of the original PID, let's verify that the process we acquired really
* is the parent still */
if (pidref->fd >= 0) {
r = pidref_get_ppid(pidref, &ppid);
if (r < 0)
return r;
/* Did the PPID change since we queried it? if so we might have pinned the wrong
* process, if its PID got reused by now. Let's try again */
if (parent.pid != ppid)
continue;
}
*ret = TAKE_PIDREF(parent);
return 0;
}
/* Give up after 16 tries */
return -ENOTRECOVERABLE;
}
int pid_get_start_time(pid_t pid, usec_t *ret) {
_cleanup_free_ char *line = NULL;
const char *p;

1
src/basic/process-util.h
View File

@ -54,6 +54,7 @@ int get_process_root(pid_t pid, char **ret);
int get_process_environ(pid_t pid, char **ret);
int pid_get_ppid(pid_t pid, pid_t *ret);
int pidref_get_ppid(const PidRef *pidref, pid_t *ret);
int pidref_get_ppid_as_pidref(const PidRef *pidref, PidRef *ret);
int pid_get_start_time(pid_t pid, usec_t *ret);
int pidref_get_start_time(const PidRef *pid, usec_t *ret);
int get_process_umask(pid_t pid, mode_t *ret);

23
src/test/test-process-util.c
View File

@ -848,6 +848,29 @@ TEST(pid_get_ppid) {
pid = ppid;
}
/* the same via pidref */
_cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
ASSERT_OK(pidref_set_self(&pidref));
for (;;) {
_cleanup_free_ char *c1 = NULL, *c2 = NULL;
_cleanup_(pidref_done) PidRef parent = PIDREF_NULL;
r = pidref_get_ppid_as_pidref(&pidref, &parent);
if (r == -EADDRNOTAVAIL) {
log_info("No further parent PID");
break;
}
ASSERT_OK(r);
ASSERT_OK(pidref_get_cmdline(&pidref, SIZE_MAX, PROCESS_CMDLINE_COMM_FALLBACK, &c1));
ASSERT_OK(pidref_get_cmdline(&parent, SIZE_MAX, PROCESS_CMDLINE_COMM_FALLBACK, &c2));
log_info("Parent of " PID_FMT " (%s) is " PID_FMT " (%s).", pidref.pid, c1, parent.pid, c2);
pidref_done(&pidref);
pidref = TAKE_PIDREF(parent);
}
}
TEST(set_oom_score_adjust) {