core: introduce new KillMode=mixed which sends SIGTERM only to the main process, but SIGKILL to all daemon processes

This should fix some race with terminating systemd --user, where the
system systemd instance might race against the user systemd instance
when sending SIGTERM.

3 files changed, 4 insertions, 1 deletions

diff --git a/src/core/kill.c b/src/core/kill.c
index ea947c23ae..4271346511 100644
--- a/src/core/kill.c
+++ b/src/core/kill.c
@@ -52,6 +52,7 @@ void kill_context_dump(KillContext *c, FILE *f, const char *prefix) {
 static const char* const kill_mode_table[_KILL_MODE_MAX] = {
         [KILL_CONTROL_GROUP] = "control-group",
         [KILL_PROCESS] = "process",
+        [KILL_MIXED] = "mixed",
         [KILL_NONE] = "none"
 };
 
diff --git a/src/core/kill.h b/src/core/kill.h
index 41773f07ae..d5f125fa41 100644
--- a/src/core/kill.h
+++ b/src/core/kill.h
@@ -32,6 +32,7 @@ typedef enum KillMode {
         /* The kill mode is a property of a unit. */
         KILL_CONTROL_GROUP = 0,
         KILL_PROCESS,
+        KILL_MIXED,
         KILL_NONE,
         _KILL_MODE_MAX,
         _KILL_MODE_INVALID = -1
diff --git a/src/core/unit.c b/src/core/unit.c
index e5ea994e54..0ad679ba62 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -2966,7 +2966,7 @@ int unit_kill_context(
                 }
         }
 
-        if (c->kill_mode == KILL_CONTROL_GROUP && u->cgroup_path) {
+        if ((c->kill_mode == KILL_CONTROL_GROUP || (c->kill_mode == KILL_MIXED && sigkill)) && u->cgroup_path) {
                 _cleanup_set_free_ Set *pid_set = NULL;
 
                 /* Exclude the main/control pids from being killed via the cgroup */
@@ -2980,6 +2980,7 @@ int unit_kill_context(
                                 log_warning_unit(u->id, "Failed to kill control group: %s", strerror(-r));
                 } else if (r > 0) {
                         wait_for_exit = true;
+
                         if (c->send_sighup) {
                                 set_free(pid_set);