core: add IgnoreOnSoftReboot= unit option

As it says on the tin, configures the unit to survive a soft reboot.
Currently all the following options have to be set by hand:

Conflicts=reboot.target kexec.target poweroff.target halt.target
Before=reboot.target kexec.target poweroff.target halt.target
After=sysinit.target basic.target
DefaultDependencies=no
IgnoreOnIsolate=yes

This is not very user friendly. If new default dependencies are added,
or new shutdown/reboot types, they also have to be added manually.

The new option is much simpler, easy to find, and does the right thing
by default.

src/core/dbus-unit.c

@@ -921,6 +921,7 @@ const sd_bus_vtable bus_unit_vtable[] = {
         SD_BUS_PROPERTY("RefuseManualStop", "b", bus_property_get_bool, offsetof(Unit, refuse_manual_stop), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("AllowIsolate", "b", bus_property_get_bool, offsetof(Unit, allow_isolate), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("DefaultDependencies", "b", bus_property_get_bool, offsetof(Unit, default_dependencies), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("IgnoreOnSoftReboot", "b", bus_property_get_bool, offsetof(Unit, ignore_on_soft_reboot), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("OnSuccesJobMode", "s", property_get_job_mode, offsetof(Unit, on_success_job_mode), SD_BUS_VTABLE_PROPERTY_CONST|SD_BUS_VTABLE_HIDDEN), /* deprecated */
         SD_BUS_PROPERTY("OnSuccessJobMode", "s", property_get_job_mode, offsetof(Unit, on_success_job_mode), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("OnFailureJobMode", "s", property_get_job_mode, offsetof(Unit, on_failure_job_mode), SD_BUS_VTABLE_PROPERTY_CONST),
@@ -2175,6 +2176,9 @@ static int bus_unit_set_transient_property(
         if (streq(name, "DefaultDependencies"))
                 return bus_set_transient_bool(u, name, &u->default_dependencies, message, flags, error);
 
+        if (streq(name, "IgnoreOnSoftReboot"))
+                return bus_set_transient_bool(u, name, &u->ignore_on_soft_reboot, message, flags, error);
+
         if (streq(name, "OnSuccessJobMode"))
                 return bus_set_transient_job_mode(u, name, &u->on_success_job_mode, message, flags, error);
 

src/core/load-fragment-gperf.gperf.in

@@ -312,6 +312,7 @@ Unit.RefuseManualStart,                  config_parse_bool,
 Unit.RefuseManualStop,                   config_parse_bool,                           0,                                  offsetof(Unit, refuse_manual_stop)
 Unit.AllowIsolate,                       config_parse_bool,                           0,                                  offsetof(Unit, allow_isolate)
 Unit.DefaultDependencies,                config_parse_bool,                           0,                                  offsetof(Unit, default_dependencies)
+Unit.IgnoreOnSoftReboot,                 config_parse_bool,                           0,                                  offsetof(Unit, ignore_on_soft_reboot)
 Unit.OnSuccessJobMode,                   config_parse_job_mode,                       0,                                  offsetof(Unit, on_success_job_mode)
 Unit.OnFailureJobMode,                   config_parse_job_mode,                       0,                                  offsetof(Unit, on_failure_job_mode)
 {# The following is a legacy alias name for compatibility #}

src/core/path.c

@@ -342,12 +342,24 @@ static int path_add_default_dependencies(Path *p) {
                 return r;
 
         if (MANAGER_IS_SYSTEM(UNIT(p)->manager)) {
-                r = unit_add_two_dependencies_by_name(UNIT(p), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                r = unit_add_two_dependencies_by_name(UNIT(p),
+                                UNIT_AFTER,
+                                UNIT(p)->ignore_on_soft_reboot ? -EINVAL : UNIT_REQUIRES,
+                                SPECIAL_SYSINIT_TARGET,
+                                true,
+                                UNIT_DEPENDENCY_DEFAULT);
                 if (r < 0)
                         return r;
         }
 
-        return unit_add_two_dependencies_by_name(UNIT(p), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (!UNIT(p)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(p),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
+
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(p));
 }
 
 static int path_add_trigger_dependencies(Path *p) {

src/core/scope.c

@@ -131,23 +131,22 @@ static void scope_set_state(Scope *s, ScopeState state) {
 }
 
 static int scope_add_default_dependencies(Scope *s) {
-        int r;
-
         assert(s);
 
         if (!UNIT(s)->default_dependencies)
                 return 0;
 
         /* Make sure scopes are unloaded on shutdown */
-        r = unit_add_two_dependencies_by_name(
-                        UNIT(s),
-                        UNIT_BEFORE, UNIT_CONFLICTS,
-                        SPECIAL_SHUTDOWN_TARGET, true,
-                        UNIT_DEPENDENCY_DEFAULT);
-        if (r < 0)
-                return r;
+        if (!UNIT(s)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(s),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
 
-        return 0;
+        /* Unless we are meant to survive soft reboot, in which case we need to conflict with
+         * non-soft-reboot targets. */
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(s));
 }
 
 static int scope_verify(Scope *s) {

src/core/service.c

@@ -722,11 +722,16 @@ static int service_add_default_dependencies(Service *s) {
          * majority of services. */
 
         if (MANAGER_IS_SYSTEM(UNIT(s)->manager)) {
-                /* First, pull in the really early boot stuff, and
-                 * require it, so that we fail if we can't acquire
-                 * it. */
+                /* First, pull in the really early boot stuff, and require it, so that we fail if we can't
+                 * acquire it. But only add ordering if this is meant to survive a soft reboot, otherwise
+                 * it will be pulled down. */
 
-                r = unit_add_two_dependencies_by_name(UNIT(s), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                r = unit_add_two_dependencies_by_name(UNIT(s),
+                                UNIT_AFTER,
+                                UNIT(s)->ignore_on_soft_reboot ? -EINVAL : UNIT_REQUIRES,
+                                SPECIAL_SYSINIT_TARGET,
+                                true,
+                                UNIT_DEPENDENCY_DEFAULT);
                 if (r < 0)
                         return r;
         } else {
@@ -747,7 +752,17 @@ static int service_add_default_dependencies(Service *s) {
                 return r;
 
         /* Third, add us in for normal shutdown. */
-        return unit_add_two_dependencies_by_name(UNIT(s), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (!UNIT(s)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(UNIT(s),
+                                UNIT_BEFORE,
+                                UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET,
+                                true,
+                                UNIT_DEPENDENCY_DEFAULT);
+
+        /* Unless we are meant to survive soft reboot, in which case we need to conflict with
+         * non-soft-reboot targets. */
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(s));
 }
 
 static void service_fix_stdio(Service *s) {

src/core/slice.c

@@ -64,22 +64,22 @@ static int slice_add_parent_slice(Slice *s) {
 }
 
 static int slice_add_default_dependencies(Slice *s) {
-        int r;
-
         assert(s);
 
         if (!UNIT(s)->default_dependencies)
                 return 0;
 
         /* Make sure slices are unloaded on shutdown */
-        r = unit_add_two_dependencies_by_name(
-                        UNIT(s),
-                        UNIT_BEFORE, UNIT_CONFLICTS,
-                        SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
-        if (r < 0)
-                return r;
+        if (!UNIT(s)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(s),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
 
-        return 0;
+        /* Unless we are meant to survive soft reboot, in which case we need to conflict with
+         * non-soft-reboot targets. */
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(s));
 }
 
 static int slice_verify(Slice *s) {

src/core/socket.c

@@ -278,12 +278,24 @@ static int socket_add_default_dependencies(Socket *s) {
                 return r;
 
         if (MANAGER_IS_SYSTEM(UNIT(s)->manager)) {
-                r = unit_add_two_dependencies_by_name(UNIT(s), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                r = unit_add_two_dependencies_by_name(UNIT(s),
+                                UNIT_AFTER,
+                                UNIT(s)->ignore_on_soft_reboot ? -EINVAL : UNIT_REQUIRES,
+                                SPECIAL_SYSINIT_TARGET,
+                                true,
+                                UNIT_DEPENDENCY_DEFAULT);
                 if (r < 0)
                         return r;
         }
 
-        return unit_add_two_dependencies_by_name(UNIT(s), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (!UNIT(s)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(s),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
+
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(s));
 }
 
 _pure_ static bool socket_has_exec(Socket *s) {

src/core/target.c

@@ -66,7 +66,16 @@ static int target_add_default_dependencies(Target *t) {
                 return 0;
 
         /* Make sure targets are unloaded on shutdown */
-        return unit_add_two_dependencies_by_name(UNIT(t), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (!UNIT(t)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(t),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
+
+        /* Unless we are meant to survive soft reboot, in which case we need to conflict with
+         * non-soft-reboot targets. */
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(t));
 }
 
 static int target_load(Unit *u) {

src/core/timer.c

@@ -94,7 +94,12 @@ static int timer_add_default_dependencies(Timer *t) {
                 return r;
 
         if (MANAGER_IS_SYSTEM(UNIT(t)->manager)) {
-                r = unit_add_two_dependencies_by_name(UNIT(t), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                r = unit_add_two_dependencies_by_name(UNIT(t),
+                                UNIT_AFTER,
+                                UNIT(t)->ignore_on_soft_reboot ? -EINVAL : UNIT_REQUIRES,
+                                SPECIAL_SYSINIT_TARGET,
+                                true,
+                                UNIT_DEPENDENCY_DEFAULT);
                 if (r < 0)
                         return r;
 
@@ -112,7 +117,14 @@ static int timer_add_default_dependencies(Timer *t) {
                 }
         }
 
-        return unit_add_two_dependencies_by_name(UNIT(t), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (!UNIT(t)->ignore_on_soft_reboot)
+                return unit_add_two_dependencies_by_name(
+                                UNIT(t),
+                                UNIT_BEFORE, UNIT_CONFLICTS,
+                                SPECIAL_SHUTDOWN_TARGET, true,
+                                UNIT_DEPENDENCY_DEFAULT);
+
+        return unit_add_dependencies_on_real_shutdown_targets(UNIT(t));
 }
 
 static int timer_add_trigger_dependencies(Timer *t) {

src/core/transaction.c

@@ -628,7 +628,7 @@ static int transaction_apply(
                 HASHMAP_FOREACH(j, m->jobs) {
                         assert(j->installed);
 
-                        if (j->unit->ignore_on_isolate)
+                        if (j->unit->ignore_on_isolate || j->unit->ignore_on_soft_reboot)
                                 continue;
 
                         if (hashmap_contains(tr->jobs, j->unit))
@@ -1159,6 +1159,9 @@ static bool shall_stop_on_isolate(Transaction *tr, Unit *u) {
         if (u->ignore_on_isolate)
                 return false;
 
+        if (u->ignore_on_soft_reboot)
+                return false;
+
         /* Is there already something listed for this? */
         if (hashmap_contains(tr->jobs, u))
                 return false;

src/core/unit-serialize.c

@@ -830,6 +830,7 @@ void unit_dump(Unit *u, FILE *f, const char *prefix) {
                         "%s\tRefuseManualStart: %s\n"
                         "%s\tRefuseManualStop: %s\n"
                         "%s\tDefaultDependencies: %s\n"
+                        "%s\tIgnoreOnSoftReboot: %s\n"
                         "%s\tOnSuccessJobMode: %s\n"
                         "%s\tOnFailureJobMode: %s\n"
                         "%s\tIgnoreOnIsolate: %s\n",
@@ -837,6 +838,7 @@ void unit_dump(Unit *u, FILE *f, const char *prefix) {
                         prefix, yes_no(u->refuse_manual_start),
                         prefix, yes_no(u->refuse_manual_stop),
                         prefix, yes_no(u->default_dependencies),
+                        prefix, yes_no(u->ignore_on_soft_reboot),
                         prefix, job_mode_to_string(u->on_success_job_mode),
                         prefix, job_mode_to_string(u->on_failure_job_mode),
                         prefix, yes_no(u->ignore_on_isolate));

src/core/unit.c

@@ -3291,19 +3291,46 @@ int unit_add_dependency(
 }
 
 int unit_add_two_dependencies(Unit *u, UnitDependency d, UnitDependency e, Unit *other, bool add_reference, UnitDependencyMask mask) {
-        int r, s;
+        int r = 0, s = 0;
+
+        assert(u);
+        assert(d >= 0 || e >= 0);
+
+        if (d >= 0) {
+                r = unit_add_dependency(u, d, other, add_reference, mask);
+                if (r < 0)
+                        return r;
+        }
+
+        if (e >= 0) {
+                s = unit_add_dependency(u, e, other, add_reference, mask);
+                if (s < 0)
+                        return s;
+        }
+
+        return r > 0 || s > 0;
+}
+
+int unit_add_dependencies_on_real_shutdown_targets(Unit *u) {
+        int r;
 
         assert(u);
 
-        r = unit_add_dependency(u, d, other, add_reference, mask);
-        if (r < 0)
-                return r;
+        STRV_FOREACH(target, STRV_MAKE(SPECIAL_REBOOT_TARGET,
+                                SPECIAL_KEXEC_TARGET,
+                                SPECIAL_HALT_TARGET,
+                                SPECIAL_POWEROFF_TARGET)) {
+                r = unit_add_two_dependencies_by_name(u,
+                                UNIT_BEFORE,
+                                UNIT_CONFLICTS,
+                                *target,
+                                /* add_reference= */ true,
+                                UNIT_DEPENDENCY_DEFAULT);
+                if (r < 0)
+                        return r;
+        }
 
-        s = unit_add_dependency(u, e, other, add_reference, mask);
-        if (s < 0)
-                return s;
-
-        return r > 0 || s > 0;
+        return 0;
 }
 
 static int resolve_template(Unit *u, const char *name, char **buf, const char **ret) {

src/core/unit.h

@@ -450,6 +450,9 @@ typedef struct Unit {
         /* Create default dependencies */
         bool default_dependencies;
 
+        /* Configure so that the unit survives a soft reboot without stopping/starting. */
+        bool ignore_on_soft_reboot;
+
         /* Refuse manual starting, allow starting only indirectly via dependency. */
         bool refuse_manual_start;
 
@@ -852,6 +855,8 @@ int unit_add_dependency_by_name(Unit *u, UnitDependency d, const char *name, boo
 int unit_add_two_dependencies_by_name(Unit *u, UnitDependency d, UnitDependency e, const char *name, bool add_reference, UnitDependencyMask mask);
 
 int unit_add_exec_dependencies(Unit *u, ExecContext *c);
+/* Helper for IgnoreOnSoftReboot units that need to survive soft-reboot.target but not others */
+int unit_add_dependencies_on_real_shutdown_targets(Unit *u);
 
 int unit_choose_id(Unit *u, const char *name);
 int unit_set_description(Unit *u, const char *description);