core: when forcibly killing/aborting left-over unit processes log about it

Let's lot at LOG_NOTICE about any processes that we are going to
SIGKILL/SIGABRT because clean termination of them didn't work.

This turns the various boolean flag parameters to cg_kill(), cg_migrate() and
related calls into a single binary flags parameter, simply because the function
now gained even more parameters and the parameter listed shouldn't get too
long.

Logging for killing processes is done either when the kill signal is SIGABRT or
SIGKILL, or on explicit request if KILL_TERMINATE_AND_LOG instead of LOG_TERMINATE
is passed. This isn't used yet in this patch, but is made use of in a later
patch.

1 files changed, 74 insertions, 24 deletions

diff --git a/src/core/unit.c b/src/core/unit.c
index fdf7ce3af3..4934a0e56f 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3144,7 +3144,7 @@ int unit_kill_common(
                 if (!pid_set)
                         return -ENOMEM;
 
-                q = cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, signo, false, false, false, pid_set);
+                q = cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, signo, 0, pid_set, NULL, NULL);
                 if (q < 0 && q != -EAGAIN && q != -ESRCH && q != -ENOENT)
                         r = q;
                 else
@@ -3512,6 +3512,43 @@ int unit_make_transient(Unit *u) {
         return 0;
 }
 
+static void log_kill(pid_t pid, int sig, void *userdata) {
+        _cleanup_free_ char *comm = NULL;
+
+        (void) get_process_comm(pid, &comm);
+
+        /* Don't log about processes marked with brackets, under the assumption that these are temporary processes
+           only, like for example systemd's own PAM stub process. */
+        if (comm && comm[0] == '(')
+                return;
+
+        log_unit_notice(userdata,
+                        "Killing process " PID_FMT " (%s) with signal SIG%s.",
+                        pid,
+                        strna(comm),
+                        signal_to_string(sig));
+}
+
+static int operation_to_signal(KillContext *c, KillOperation k) {
+        assert(c);
+
+        switch (k) {
+
+        case KILL_TERMINATE:
+        case KILL_TERMINATE_AND_LOG:
+                return c->kill_signal;
+
+        case KILL_KILL:
+                return SIGKILL;
+
+        case KILL_ABORT:
+                return SIGABRT;
+
+        default:
+                assert_not_reached("KillOperation unknown");
+        }
+}
+
 int unit_kill_context(
                 Unit *u,
                 KillContext *c,
@@ -3520,58 +3557,63 @@ int unit_kill_context(
                 pid_t control_pid,
                 bool main_pid_alien) {
 
-        bool wait_for_exit = false;
+        bool wait_for_exit = false, send_sighup;
+        cg_kill_log_func_t log_func;
         int sig, r;
 
         assert(u);
         assert(c);
 
+        /* Kill the processes belonging to this unit, in preparation for shutting the unit down. Returns > 0 if we
+         * killed something worth waiting for, 0 otherwise. */
+
         if (c->kill_mode == KILL_NONE)
                 return 0;
 
-        switch (k) {
-        case KILL_KILL:
-                sig = SIGKILL;
-                break;
-        case KILL_ABORT:
-                sig = SIGABRT;
-                break;
-        case KILL_TERMINATE:
-                sig = c->kill_signal;
-                break;
-        default:
-                assert_not_reached("KillOperation unknown");
-        }
+        sig = operation_to_signal(c, k);
+
+        send_sighup =
+                c->send_sighup &&
+                IN_SET(k, KILL_TERMINATE, KILL_TERMINATE_AND_LOG) &&
+                sig != SIGHUP;
+
+        log_func =
+                k != KILL_TERMINATE ||
+                IN_SET(sig, SIGKILL, SIGABRT) ? log_kill : NULL;
 
         if (main_pid > 0) {
-                r = kill_and_sigcont(main_pid, sig);
+                if (log_func)
+                        log_func(main_pid, sig, u);
 
+                r = kill_and_sigcont(main_pid, sig);
                 if (r < 0 && r != -ESRCH) {
                         _cleanup_free_ char *comm = NULL;
-                        get_process_comm(main_pid, &comm);
+                        (void) get_process_comm(main_pid, &comm);
 
                         log_unit_warning_errno(u, r, "Failed to kill main process " PID_FMT " (%s), ignoring: %m", main_pid, strna(comm));
                 } else {
                         if (!main_pid_alien)
                                 wait_for_exit = true;
 
-                        if (c->send_sighup && k == KILL_TERMINATE)
+                        if (r != -ESRCH && send_sighup)
                                 (void) kill(main_pid, SIGHUP);
                 }
         }
 
         if (control_pid > 0) {
-                r = kill_and_sigcont(control_pid, sig);
+                if (log_func)
+                        log_func(control_pid, sig, u);
 
+                r = kill_and_sigcont(control_pid, sig);
                 if (r < 0 && r != -ESRCH) {
                         _cleanup_free_ char *comm = NULL;
-                        get_process_comm(control_pid, &comm);
+                        (void) get_process_comm(control_pid, &comm);
 
                         log_unit_warning_errno(u, r, "Failed to kill control process " PID_FMT " (%s), ignoring: %m", control_pid, strna(comm));
                 } else {
                         wait_for_exit = true;
 
-                        if (c->send_sighup && k == KILL_TERMINATE)
+                        if (r != -ESRCH && send_sighup)
                                 (void) kill(control_pid, SIGHUP);
                 }
         }
@@ -3585,7 +3627,11 @@ int unit_kill_context(
                 if (!pid_set)
                         return -ENOMEM;
 
-                r = cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, sig, true, k != KILL_TERMINATE, false, pid_set);
+                r = cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path,
+                                      sig,
+                                      CGROUP_SIGCONT|CGROUP_IGNORE_SELF,
+                                      pid_set,
+                                      log_func, u);
                 if (r < 0) {
                         if (r != -EAGAIN && r != -ESRCH && r != -ENOENT)
                                 log_unit_warning_errno(u, r, "Failed to kill control group %s, ignoring: %m", u->cgroup_path);
@@ -3610,14 +3656,18 @@ int unit_kill_context(
                              (detect_container() == 0 && !unit_cgroup_delegate(u)))
                                 wait_for_exit = true;
 
-                        if (c->send_sighup && k != KILL_KILL) {
+                        if (send_sighup) {
                                 set_free(pid_set);
 
                                 pid_set = unit_pid_set(main_pid, control_pid);
                                 if (!pid_set)
                                         return -ENOMEM;
 
-                                cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, SIGHUP, false, true, false, pid_set);
+                                cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path,
+                                                  SIGHUP,
+                                                  CGROUP_IGNORE_SELF,
+                                                  pid_set,
+                                                  NULL, NULL);
                         }
                 }
         }