Merge pull request #29454 from poettering/cg-pidref-get-path

cgroup-util: add cg_pidref_get_path() helper and use it

TODO

@@ -209,7 +209,6 @@ Features:
   - pid_is_alive() → pidref_is_alive()
   - is_kernel_thread() → pidref_is_kernel_thread()
   - pid_is_my_child() → pidref_is_my_child()
-  - cg_pid_get_path() → cg_pidref_get_path()
   - get_process_uid() → pidref_get_uid()
   - actually wait for POLLIN on pidref's pidfd in service logic
   - exec_spawn()

src/basic/cgroup-util.c

@@ -809,6 +809,28 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **ret_path) {
         }
 }
 
+int cg_pidref_get_path(const char *controller, PidRef *pidref, char **ret_path) {
+        _cleanup_free_ char *path = NULL;
+        int r;
+
+        assert(ret_path);
+
+        if (!pidref_is_set(pidref))
+                return -ESRCH;
+
+        r = cg_pid_get_path(controller, pidref->pid, &path);
+        if (r < 0)
+                return r;
+
+        /* Before we return the path, make sure the procfs entry for this pid still matches the pidref */
+        r = pidref_verify(pidref);
+        if (r < 0)
+                return r;
+
+        *ret_path = TAKE_PTR(path);
+        return 0;
+}
+
 int cg_install_release_agent(const char *controller, const char *agent) {
         _cleanup_free_ char *fs = NULL, *contents = NULL;
         const char *sc;

src/basic/cgroup-util.h

@@ -204,6 +204,7 @@ int cg_get_path(const char *controller, const char *path, const char *suffix, ch
 int cg_get_path_and_check(const char *controller, const char *path, const char *suffix, char **fs);
 
 int cg_pid_get_path(const char *controller, pid_t pid, char **path);
+int cg_pidref_get_path(const char *controller, PidRef *pidref, char **path);
 
 int cg_rmdir(const char *controller, const char *path);
 

src/core/cgroup.c

@@ -3784,10 +3784,7 @@ Unit *manager_get_unit_by_pidref_cgroup(Manager *m, PidRef *pid) {
 
         assert(m);
 
-        if (!pidref_is_set(pid))
-                return NULL;
-
-        if (cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid->pid, &cgroup) < 0)
+        if (cg_pidref_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup) < 0)
                 return NULL;
 
         return manager_get_unit_by_cgroup(m, cgroup);