process-util: add pidref_is_kernel_thread()

src/basic/process-util.c

@@ -389,7 +389,7 @@ int namespace_get_leader(pid_t pid, NamespaceType type, pid_t *ret) {
         }
 }
 
-int is_kernel_thread(pid_t pid) {
+int pid_is_kernel_thread(pid_t pid) {
         _cleanup_free_ char *line = NULL;
         unsigned long long flags;
         size_t l, i;
@@ -447,6 +447,23 @@ int is_kernel_thread(pid_t pid) {
         return !!(flags & PF_KTHREAD);
 }
 
+int pidref_is_kernel_thread(const PidRef *pid) {
+        int result, r;
+
+        if (!pidref_is_set(pid))
+                return -ESRCH;
+
+        result = pid_is_kernel_thread(pid->pid);
+        if (result < 0)
+                return result;
+
+        r = pidref_verify(pid); /* Verify that the PID wasn't reused since */
+        if (r < 0)
+                return r;
+
+        return result;
+}
+
 int get_process_capeff(pid_t pid, char **ret) {
         const char *p;
         int r;

src/basic/process-util.h

@@ -79,7 +79,8 @@ void sigkill_nowaitp(pid_t *pid);
 
 int kill_and_sigcont(pid_t pid, int sig);
 
-int is_kernel_thread(pid_t pid);
+int pid_is_kernel_thread(pid_t pid);
+int pidref_is_kernel_thread(const PidRef *pid);
 
 int getenv_for_pid(pid_t pid, const char *field, char **_value);
 

src/cgtop/cgtop.c

@@ -209,7 +209,7 @@ static int process(
                 g->n_tasks = 0;
                 while (cg_read_pid(f, &pid) > 0) {
 
-                        if (arg_count == COUNT_USERSPACE_PROCESSES && is_kernel_thread(pid) > 0)
+                        if (arg_count == COUNT_USERSPACE_PROCESSES && pid_is_kernel_thread(pid) > 0)
                                 continue;
 
                         g->n_tasks++;

src/core/dbus-unit.c

@@ -1295,7 +1295,7 @@ static int append_cgroup(sd_bus_message *reply, const char *p, Set *pids) {
                 if (r < 0)
                         return r;
 
-                if (is_kernel_thread(pid) > 0)
+                if (pid_is_kernel_thread(pid) > 0)
                         continue;
 
                 r = append_process(reply, p, pid, pids);

src/core/unit.c

@@ -5953,7 +5953,7 @@ int unit_pid_attachable(Unit *u, PidRef *pid, sd_bus_error *error) {
                 return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Process " PID_FMT " is a manager process, refusing.", pid->pid);
 
         /* Don't even begin to bother with kernel threads */
-        r = is_kernel_thread(pid->pid);
+        r = pidref_is_kernel_thread(pid);
         if (r == -ESRCH)
                 return sd_bus_error_setf(error, SD_BUS_ERROR_UNIX_PROCESS_ID_UNKNOWN, "Process with ID " PID_FMT " does not exist.", pid->pid);
         if (r < 0)

src/shared/cgroup-setup.c

@@ -611,7 +611,7 @@ int cg_migrate(
                          * them there. */
                         if (cfrom &&
                             empty_or_root(pfrom) &&
-                            is_kernel_thread(pid) > 0)
+                            pid_is_kernel_thread(pid) > 0)
                                 continue;
 
                         r = cg_attach(cto, pto, pid);

src/shared/cgroup-show.c

@@ -114,7 +114,7 @@ static int show_cgroup_one_by_path(
                 if (r < 0)
                         return r;
 
-                if (!(flags & OUTPUT_KERNEL_THREADS) && is_kernel_thread(pid) > 0)
+                if (!(flags & OUTPUT_KERNEL_THREADS) && pid_is_kernel_thread(pid) > 0)
                         continue;
 
                 if (!GREEDY_REALLOC(pids, n + 1))

src/shared/killall.c

@@ -77,7 +77,7 @@ static bool ignore_proc(pid_t pid, bool warn_rootfs) {
                 return true;
 
         /* Ignore kernel threads */
-        r = is_kernel_thread(pid);
+        r = pid_is_kernel_thread(pid);
         if (r != 0)
                 return true; /* also ignore processes where we can't determine this */
 

src/test/test-cgroup-util.c

@@ -209,7 +209,7 @@ TEST(proc) {
                 if (r < 0)
                         continue;
 
-                if (is_kernel_thread(pid))
+                if (pid_is_kernel_thread(pid) != 0)
                         continue;
 
                 cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &path);

src/test/test-process-util.c

@@ -76,7 +76,7 @@ static void test_get_process_comm_one(pid_t pid) {
                 assert_se(e > 0);
         }
 
-        assert_se(is_kernel_thread(pid) == 0 || pid != 1);
+        assert_se(pid_is_kernel_thread(pid) == 0 || pid != 1);
 
         r = get_process_exe(pid, &f);
         assert_se(r >= 0 || r == -EACCES);