Merge pull request #3170 from poettering/v230-preparation-fixes

make virtualization detection quieter, rework unit start limit logic, detect unit file drop-in changes correctly, fix autofs state propagation

18 files changed, 165 insertions, 104 deletions

diff --git a/src/core/automount.c b/src/core/automount.c
index 1239a0efc6..f06d837e30 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -75,6 +75,9 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(struct expire_data*, expire_data_free);
 
 static int open_dev_autofs(Manager *m);
 static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, void *userdata);
+static int automount_start_expire(Automount *a);
+static void automount_stop_expire(Automount *a);
+static int automount_send_ready(Automount *a, Set *tokens, int status);
 
 static void automount_init(Unit *u) {
         Automount *a = AUTOMOUNT(u);
@@ -87,8 +90,6 @@ static void automount_init(Unit *u) {
         UNIT(a)->ignore_on_isolate = true;
 }
 
-static int automount_send_ready(Automount *a, Set *tokens, int status);
-
 static void unmount_autofs(Automount *a) {
         int r;
 
@@ -235,6 +236,9 @@ static void automount_set_state(Automount *a, AutomountState state) {
         old_state = a->state;
         a->state = state;
 
+        if (state != AUTOMOUNT_RUNNING)
+                automount_stop_expire(a);
+
         if (state != AUTOMOUNT_WAITING &&
             state != AUTOMOUNT_RUNNING)
                 unmount_autofs(a);
@@ -408,7 +412,7 @@ static int autofs_send_ready(int dev_autofs_fd, int ioctl_fd, uint32_t token, in
         init_autofs_dev_ioctl(&param);
         param.ioctlfd = ioctl_fd;
 
-        if (status) {
+        if (status != 0) {
                 param.fail.token = token;
                 param.fail.status = status;
         } else
@@ -435,7 +439,7 @@ static int automount_send_ready(Automount *a, Set *tokens, int status) {
         if (ioctl_fd < 0)
                 return ioctl_fd;
 
-        if (status)
+        if (status != 0)
                 log_unit_debug_errno(UNIT(a), status, "Sending failure: %m");
         else
                 log_unit_debug(UNIT(a), "Sending success.");
@@ -462,59 +466,54 @@ static int automount_send_ready(Automount *a, Set *tokens, int status) {
         return r;
 }
 
-static int automount_start_expire(Automount *a);
-
-int automount_update_mount(Automount *a, MountState old_state, MountState state) {
+static void automount_trigger_notify(Unit *u, Unit *other) {
+        Automount *a = AUTOMOUNT(u);
         int r;
 
         assert(a);
+        assert(other);
+
+        /* Filter out invocations with bogus state */
+        if (other->load_state != UNIT_LOADED || other->type != UNIT_MOUNT)
+                return;
+
+        /* Don't propagate state changes from the mount if we are already down */
+        if (!IN_SET(a->state, AUTOMOUNT_WAITING, AUTOMOUNT_RUNNING))
+                return;
+
+        /* Propagate start limit hit state */
+        if (other->start_limit_hit) {
+                automount_enter_dead(a, AUTOMOUNT_FAILURE_MOUNT_START_LIMIT_HIT);
+                return;
+        }
+
+        /* Don't propagate anything if there's still a job queued */
+        if (other->job)
+                return;
+
+        /* The mount is successfully established */
+        if (IN_SET(MOUNT(other)->state, MOUNT_MOUNTED, MOUNT_REMOUNTING)) {
+                (void) automount_send_ready(a, a->tokens, 0);
 
-        switch (state) {
-        case MOUNT_MOUNTED:
-        case MOUNT_REMOUNTING:
-                automount_send_ready(a, a->tokens, 0);
                 r = automount_start_expire(a);
                 if (r < 0)
                         log_unit_warning_errno(UNIT(a), r, "Failed to start expiration timer, ignoring: %m");
-                break;
-         case MOUNT_DEAD:
-         case MOUNT_UNMOUNTING:
-         case MOUNT_MOUNTING_SIGTERM:
-         case MOUNT_MOUNTING_SIGKILL:
-         case MOUNT_REMOUNTING_SIGTERM:
-         case MOUNT_REMOUNTING_SIGKILL:
-         case MOUNT_UNMOUNTING_SIGTERM:
-         case MOUNT_UNMOUNTING_SIGKILL:
-         case MOUNT_FAILED:
-                if (old_state != state)
-                        automount_send_ready(a, a->tokens, -ENODEV);
-                (void) sd_event_source_set_enabled(a->expire_event_source, SD_EVENT_OFF);
-                break;
-        default:
-                break;
-        }
 
-        switch (state) {
-        case MOUNT_DEAD:
-                automount_send_ready(a, a->expire_tokens, 0);
-                break;
-         case MOUNT_MOUNTING:
-         case MOUNT_MOUNTING_DONE:
-         case MOUNT_MOUNTING_SIGTERM:
-         case MOUNT_MOUNTING_SIGKILL:
-         case MOUNT_REMOUNTING_SIGTERM:
-         case MOUNT_REMOUNTING_SIGKILL:
-         case MOUNT_UNMOUNTING_SIGTERM:
-         case MOUNT_UNMOUNTING_SIGKILL:
-         case MOUNT_FAILED:
-                if (old_state != state)
-                        automount_send_ready(a, a->expire_tokens, -ENODEV);
-                break;
-        default:
-                break;
+                automount_set_state(a, AUTOMOUNT_RUNNING);
         }
 
-        return 0;
+        /* The mount is in some unhappy state now, let's unfreeze any waiting clients */
+        if (IN_SET(MOUNT(other)->state,
+                   MOUNT_DEAD, MOUNT_UNMOUNTING,
+                   MOUNT_MOUNTING_SIGTERM, MOUNT_MOUNTING_SIGKILL,
+                   MOUNT_REMOUNTING_SIGTERM, MOUNT_REMOUNTING_SIGKILL,
+                   MOUNT_UNMOUNTING_SIGTERM, MOUNT_UNMOUNTING_SIGKILL,
+                   MOUNT_FAILED)) {
+
+                (void) automount_send_ready(a, a->tokens, -ENODEV);
+
+                automount_set_state(a, AUTOMOUNT_WAITING);
+        }
 }
 
 static void automount_enter_waiting(Automount *a) {
@@ -699,6 +698,15 @@ static int automount_start_expire(Automount *a) {
         return 0;
 }
 
+static void automount_stop_expire(Automount *a) {
+        assert(a);
+
+        if (!a->expire_event_source)
+                return;
+
+        (void) sd_event_source_set_enabled(a->expire_event_source, SD_EVENT_OFF);
+}
+
 static void automount_enter_runnning(Automount *a) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         struct stat st;
@@ -751,6 +759,7 @@ fail:
 static int automount_start(Unit *u) {
         Automount *a = AUTOMOUNT(u);
         Unit *trigger;
+        int r;
 
         assert(a);
         assert(a->state == AUTOMOUNT_DEAD || a->state == AUTOMOUNT_FAILED);
@@ -766,6 +775,12 @@ static int automount_start(Unit *u) {
                 return -ENOENT;
         }
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                automount_enter_dead(a, AUTOMOUNT_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         a->result = AUTOMOUNT_SUCCESS;
         automount_enter_waiting(a);
         return 1;
@@ -958,7 +973,7 @@ static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, vo
         case autofs_ptype_expire_direct:
                 log_unit_debug(UNIT(a), "Got direct umount request on %s", a->where);
 
-                (void) sd_event_source_set_enabled(a->expire_event_source, SD_EVENT_OFF);
+                automount_stop_expire(a);
 
                 r = set_ensure_allocated(&a->expire_tokens, NULL);
                 if (r < 0) {
@@ -1037,7 +1052,9 @@ static bool automount_supported(void) {
 
 static const char* const automount_result_table[_AUTOMOUNT_RESULT_MAX] = {
         [AUTOMOUNT_SUCCESS] = "success",
-        [AUTOMOUNT_FAILURE_RESOURCES] = "resources"
+        [AUTOMOUNT_FAILURE_RESOURCES] = "resources",
+        [AUTOMOUNT_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
+        [AUTOMOUNT_FAILURE_MOUNT_START_LIMIT_HIT] = "mount-start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(automount_result, AutomountResult);
@@ -1069,6 +1086,8 @@ const UnitVTable automount_vtable = {
 
         .check_gc = automount_check_gc,
 
+        .trigger_notify = automount_trigger_notify,
+
         .reset_failed = automount_reset_failed,
 
         .bus_vtable = bus_automount_vtable,
diff --git a/src/core/automount.h b/src/core/automount.h
index cf5b1cf994..76a201178e 100644
--- a/src/core/automount.h
+++ b/src/core/automount.h
@@ -26,6 +26,8 @@ typedef struct Automount Automount;
 typedef enum AutomountResult {
         AUTOMOUNT_SUCCESS,
         AUTOMOUNT_FAILURE_RESOURCES,
+        AUTOMOUNT_FAILURE_START_LIMIT_HIT,
+        AUTOMOUNT_FAILURE_MOUNT_START_LIMIT_HIT,
         _AUTOMOUNT_RESULT_MAX,
         _AUTOMOUNT_RESULT_INVALID = -1
 } AutomountResult;
@@ -53,7 +55,5 @@ struct Automount {
 
 extern const UnitVTable automount_vtable;
 
-int automount_update_mount(Automount *a, MountState old_state, MountState state);
-
 const char* automount_result_to_string(AutomountResult i) _const_;
 AutomountResult automount_result_from_string(const char *s) _pure_;
diff --git a/src/core/busname.c b/src/core/busname.c
index e7b7b5c012..f03a95c24e 100644
--- a/src/core/busname.c
+++ b/src/core/busname.c
@@ -607,6 +607,7 @@ fail:
 
 static int busname_start(Unit *u) {
         BusName *n = BUSNAME(u);
+        int r;
 
         assert(n);
 
@@ -632,6 +633,12 @@ static int busname_start(Unit *u) {
 
         assert(IN_SET(n->state, BUSNAME_DEAD, BUSNAME_FAILED));
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                busname_enter_dead(n, BUSNAME_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         n->result = BUSNAME_SUCCESS;
         busname_enter_making(n);
 
@@ -1014,6 +1021,7 @@ static const char* const busname_result_table[_BUSNAME_RESULT_MAX] = {
         [BUSNAME_FAILURE_EXIT_CODE] = "exit-code",
         [BUSNAME_FAILURE_SIGNAL] = "signal",
         [BUSNAME_FAILURE_CORE_DUMP] = "core-dump",
+        [BUSNAME_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
         [BUSNAME_FAILURE_SERVICE_START_LIMIT_HIT] = "service-start-limit-hit",
 };
 
diff --git a/src/core/busname.h b/src/core/busname.h
index 52c4055dbb..a8562db458 100644
--- a/src/core/busname.h
+++ b/src/core/busname.h
@@ -32,6 +32,7 @@ typedef enum BusNameResult {
         BUSNAME_FAILURE_EXIT_CODE,
         BUSNAME_FAILURE_SIGNAL,
         BUSNAME_FAILURE_CORE_DUMP,
+        BUSNAME_FAILURE_START_LIMIT_HIT,
         BUSNAME_FAILURE_SERVICE_START_LIMIT_HIT,
         _BUSNAME_RESULT_MAX,
         _BUSNAME_RESULT_INVALID = -1
diff --git a/src/core/mount.c b/src/core/mount.c
index c8a898e4dc..5a8c26b9e1 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -584,23 +584,6 @@ static int mount_load(Unit *u) {
         return mount_verify(m);
 }
 
-static int mount_notify_automount(Mount *m, MountState old_state, MountState state) {
-        Unit *p;
-        int r;
-        Iterator i;
-
-        assert(m);
-
-        SET_FOREACH(p, UNIT(m)->dependencies[UNIT_TRIGGERED_BY], i)
-                if (p->type == UNIT_AUTOMOUNT) {
-                         r = automount_update_mount(AUTOMOUNT(p), old_state, state);
-                         if (r < 0)
-                                 return r;
-                }
-
-        return 0;
-}
-
 static void mount_set_state(Mount *m, MountState state) {
         MountState old_state;
         assert(m);
@@ -624,8 +607,6 @@ static void mount_set_state(Mount *m, MountState state) {
                 m->control_command_id = _MOUNT_EXEC_COMMAND_INVALID;
         }
 
-        mount_notify_automount(m, old_state, state);
-
         if (state != old_state)
                 log_unit_debug(UNIT(m), "Changed %s -> %s", mount_state_to_string(old_state), mount_state_to_string(state));
 
@@ -984,6 +965,7 @@ fail:
 
 static int mount_start(Unit *u) {
         Mount *m = MOUNT(u);
+        int r;
 
         assert(m);
 
@@ -1002,6 +984,12 @@ static int mount_start(Unit *u) {
 
         assert(m->state == MOUNT_DEAD || m->state == MOUNT_FAILED);
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                mount_enter_dead(m, MOUNT_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         m->result = MOUNT_SUCCESS;
         m->reload_result = MOUNT_SUCCESS;
         m->reset_cpu_usage = true;
@@ -1821,7 +1809,8 @@ static const char* const mount_result_table[_MOUNT_RESULT_MAX] = {
         [MOUNT_FAILURE_TIMEOUT] = "timeout",
         [MOUNT_FAILURE_EXIT_CODE] = "exit-code",
         [MOUNT_FAILURE_SIGNAL] = "signal",
-        [MOUNT_FAILURE_CORE_DUMP] = "core-dump"
+        [MOUNT_FAILURE_CORE_DUMP] = "core-dump",
+        [MOUNT_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(mount_result, MountResult);
diff --git a/src/core/mount.h b/src/core/mount.h
index 3b343c6b1f..da529c44f4 100644
--- a/src/core/mount.h
+++ b/src/core/mount.h
@@ -39,6 +39,7 @@ typedef enum MountResult {
         MOUNT_FAILURE_EXIT_CODE,
         MOUNT_FAILURE_SIGNAL,
         MOUNT_FAILURE_CORE_DUMP,
+        MOUNT_FAILURE_START_LIMIT_HIT,
         _MOUNT_RESULT_MAX,
         _MOUNT_RESULT_INVALID = -1
 } MountResult;
diff --git a/src/core/path.c b/src/core/path.c
index 5e7b3eb234..0dd0d375d8 100644
--- a/src/core/path.c
+++ b/src/core/path.c
@@ -560,6 +560,7 @@ static void path_mkdir(Path *p) {
 static int path_start(Unit *u) {
         Path *p = PATH(u);
         Unit *trigger;
+        int r;
 
         assert(p);
         assert(p->state == PATH_DEAD || p->state == PATH_FAILED);
@@ -570,6 +571,12 @@ static int path_start(Unit *u) {
                 return -ENOENT;
         }
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                path_enter_dead(p, PATH_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         path_mkdir(p);
 
         p->result = PATH_SUCCESS;
@@ -739,6 +746,7 @@ DEFINE_STRING_TABLE_LOOKUP(path_type, PathType);
 static const char* const path_result_table[_PATH_RESULT_MAX] = {
         [PATH_SUCCESS] = "success",
         [PATH_FAILURE_RESOURCES] = "resources",
+        [PATH_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);
diff --git a/src/core/path.h b/src/core/path.h
index bbbcebd78e..4230c8fb99 100644
--- a/src/core/path.h
+++ b/src/core/path.h
@@ -62,6 +62,7 @@ static inline bool path_spec_owns_inotify_fd(PathSpec *s, int fd) {
 typedef enum PathResult {
         PATH_SUCCESS,
         PATH_FAILURE_RESOURCES,
+        PATH_FAILURE_START_LIMIT_HIT,
         _PATH_RESULT_MAX,
         _PATH_RESULT_INVALID = -1
 } PathResult;
diff --git a/src/core/service.c b/src/core/service.c
index f7a3fcf2b9..7ebabca5d6 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -1957,6 +1957,7 @@ fail:
 
 static int service_start(Unit *u) {
         Service *s = SERVICE(u);
+        int r;
 
         assert(s);
 
@@ -1983,6 +1984,13 @@ static int service_start(Unit *u) {
 
         assert(IN_SET(s->state, SERVICE_DEAD, SERVICE_FAILED));
 
+        /* Make sure we don't enter a busy loop of some kind. */
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                service_enter_dead(s, SERVICE_FAILURE_START_LIMIT_HIT, false);
+                return r;
+        }
+
         s->result = SERVICE_SUCCESS;
         s->reload_result = SERVICE_SUCCESS;
         s->main_pid_known = false;
@@ -3266,6 +3274,7 @@ static const char* const service_result_table[_SERVICE_RESULT_MAX] = {
         [SERVICE_FAILURE_SIGNAL] = "signal",
         [SERVICE_FAILURE_CORE_DUMP] = "core-dump",
         [SERVICE_FAILURE_WATCHDOG] = "watchdog",
+        [SERVICE_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(service_result, ServiceResult);
diff --git a/src/core/service.h b/src/core/service.h
index c7f1e81bdb..4af3d40439 100644
--- a/src/core/service.h
+++ b/src/core/service.h
@@ -86,6 +86,7 @@ typedef enum ServiceResult {
         SERVICE_FAILURE_SIGNAL,
         SERVICE_FAILURE_CORE_DUMP,
         SERVICE_FAILURE_WATCHDOG,
+        SERVICE_FAILURE_START_LIMIT_HIT,
         _SERVICE_RESULT_MAX,
         _SERVICE_RESULT_INVALID = -1
 } ServiceResult;
diff --git a/src/core/socket.c b/src/core/socket.c
index 7eeed068bd..d3d4866fe6 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -2057,6 +2057,7 @@ fail:
 
 static int socket_start(Unit *u) {
         Socket *s = SOCKET(u);
+        int r;
 
         assert(s);
 
@@ -2101,6 +2102,12 @@ static int socket_start(Unit *u) {
 
         assert(s->state == SOCKET_DEAD || s->state == SOCKET_FAILED);
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                socket_enter_dead(s, SOCKET_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         s->result = SOCKET_SUCCESS;
         s->reset_cpu_usage = true;
 
@@ -2735,17 +2742,26 @@ static void socket_trigger_notify(Unit *u, Unit *other) {
         assert(u);
         assert(other);
 
-        /* Don't propagate state changes from the service if we are
-           already down or accepting connections */
-        if (!IN_SET(s->state, SOCKET_RUNNING, SOCKET_LISTENING) || s->accept)
+        /* Filter out invocations with bogus state */
+        if (other->load_state != UNIT_LOADED || other->type != UNIT_SERVICE)
+                return;
+
+        /* Don't propagate state changes from the service if we are already down */
+        if (!IN_SET(s->state, SOCKET_RUNNING, SOCKET_LISTENING))
+                return;
+
+        /* We don't care for the service state if we are in Accept=yes mode */
+        if (s->accept)
                 return;
 
+        /* Propagate start limit hit state */
         if (other->start_limit_hit) {
                 socket_enter_stop_pre(s, SOCKET_FAILURE_SERVICE_START_LIMIT_HIT);
                 return;
         }
 
-        if (other->load_state != UNIT_LOADED || other->type != UNIT_SERVICE)
+        /* Don't propagate anything if there's still a job queued */
+        if (other->job)
                 return;
 
         if (IN_SET(SERVICE(other)->state,
@@ -2818,6 +2834,7 @@ static const char* const socket_result_table[_SOCKET_RESULT_MAX] = {
         [SOCKET_FAILURE_EXIT_CODE] = "exit-code",
         [SOCKET_FAILURE_SIGNAL] = "signal",
         [SOCKET_FAILURE_CORE_DUMP] = "core-dump",
+        [SOCKET_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
         [SOCKET_FAILURE_TRIGGER_LIMIT_HIT] = "trigger-limit-hit",
         [SOCKET_FAILURE_SERVICE_START_LIMIT_HIT] = "service-start-limit-hit"
 };
diff --git a/src/core/socket.h b/src/core/socket.h
index 2a4b1bb674..0f1ac69c6f 100644
--- a/src/core/socket.h
+++ b/src/core/socket.h
@@ -52,6 +52,7 @@ typedef enum SocketResult {
         SOCKET_FAILURE_EXIT_CODE,
         SOCKET_FAILURE_SIGNAL,
         SOCKET_FAILURE_CORE_DUMP,
+        SOCKET_FAILURE_START_LIMIT_HIT,
         SOCKET_FAILURE_TRIGGER_LIMIT_HIT,
         SOCKET_FAILURE_SERVICE_START_LIMIT_HIT,
         _SOCKET_RESULT_MAX,
diff --git a/src/core/swap.c b/src/core/swap.c
index c018648d87..a532b15be8 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -814,6 +814,7 @@ fail:
 
 static int swap_start(Unit *u) {
         Swap *s = SWAP(u), *other;
+        int r;
 
         assert(s);
 
@@ -842,6 +843,12 @@ static int swap_start(Unit *u) {
                 if (UNIT(other)->job && UNIT(other)->job->state == JOB_RUNNING)
                         return -EAGAIN;
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                swap_enter_dead(s, SWAP_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         s->result = SWAP_SUCCESS;
         s->reset_cpu_usage = true;
 
@@ -1447,7 +1454,8 @@ static const char* const swap_result_table[_SWAP_RESULT_MAX] = {
         [SWAP_FAILURE_TIMEOUT] = "timeout",
         [SWAP_FAILURE_EXIT_CODE] = "exit-code",
         [SWAP_FAILURE_SIGNAL] = "signal",
-        [SWAP_FAILURE_CORE_DUMP] = "core-dump"
+        [SWAP_FAILURE_CORE_DUMP] = "core-dump",
+        [SWAP_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(swap_result, SwapResult);
diff --git a/src/core/swap.h b/src/core/swap.h
index ac7a63d81b..fbf66debdc 100644
--- a/src/core/swap.h
+++ b/src/core/swap.h
@@ -38,6 +38,7 @@ typedef enum SwapResult {
         SWAP_FAILURE_EXIT_CODE,
         SWAP_FAILURE_SIGNAL,
         SWAP_FAILURE_CORE_DUMP,
+        SWAP_FAILURE_START_LIMIT_HIT,
         _SWAP_RESULT_MAX,
         _SWAP_RESULT_INVALID = -1
 } SwapResult;
diff --git a/src/core/timer.c b/src/core/timer.c
index f8f5f4b2e4..3206296f09 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -599,6 +599,7 @@ static int timer_start(Unit *u) {
         Timer *t = TIMER(u);
         TimerValue *v;
         Unit *trigger;
+        int r;
 
         assert(t);
         assert(t->state == TIMER_DEAD || t->state == TIMER_FAILED);
@@ -609,6 +610,12 @@ static int timer_start(Unit *u) {
                 return -ENOENT;
         }
 
+        r = unit_start_limit_test(u);
+        if (r < 0) {
+                timer_enter_dead(t, TIMER_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
         t->last_trigger = DUAL_TIMESTAMP_NULL;
 
         /* Reenable all timers that depend on unit activation time */
@@ -808,7 +815,8 @@ DEFINE_STRING_TABLE_LOOKUP(timer_base, TimerBase);
 
 static const char* const timer_result_table[_TIMER_RESULT_MAX] = {
         [TIMER_SUCCESS] = "success",
-        [TIMER_FAILURE_RESOURCES] = "resources"
+        [TIMER_FAILURE_RESOURCES] = "resources",
+        [TIMER_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(timer_result, TimerResult);
diff --git a/src/core/timer.h b/src/core/timer.h
index 698e6da2f5..9c4b64f898 100644
--- a/src/core/timer.h
+++ b/src/core/timer.h
@@ -48,6 +48,7 @@ typedef struct TimerValue {
 typedef enum TimerResult {
         TIMER_SUCCESS,
         TIMER_FAILURE_RESOURCES,
+        TIMER_FAILURE_START_LIMIT_HIT,
         _TIMER_RESULT_MAX,
         _TIMER_RESULT_INVALID = -1
 } TimerResult;
diff --git a/src/core/unit.c b/src/core/unit.c
index 4ace6b075b..8153515e89 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1462,7 +1462,7 @@ void unit_status_emit_starting_stopping_reloading(Unit *u, JobType t) {
         unit_status_print_starting_stopping(u, t);
 }
 
-static int unit_start_limit_test(Unit *u) {
+int unit_start_limit_test(Unit *u) {
         assert(u);
 
         if (ratelimit_test(&u->start_limit)) {
@@ -1488,7 +1488,6 @@ static int unit_start_limit_test(Unit *u) {
 int unit_start(Unit *u) {
         UnitActiveState state;
         Unit *following;
-        int r;
 
         assert(u);
 
@@ -1541,11 +1540,6 @@ int unit_start(Unit *u) {
         if (!UNIT_VTABLE(u)->start)
                 return -EBADR;
 
-        /* Make sure we don't enter a busy loop of some kind. */
-        r = unit_start_limit_test(u);
-        if (r < 0)
-                return r;
-
         /* We don't suppress calls to ->start() here when we are
          * already starting, to allow this request to be used as a
          * "hurry up" call, for example when the unit is in some "auto
@@ -2951,7 +2945,7 @@ int unit_coldplug(Unit *u) {
         return 0;
 }
 
-static bool fragment_mtime_changed(const char *path, usec_t mtime) {
+static bool fragment_mtime_newer(const char *path, usec_t mtime) {
         struct stat st;
 
         if (!path)
@@ -2963,7 +2957,7 @@ static bool fragment_mtime_changed(const char *path, usec_t mtime) {
 
         if (mtime > 0)
                 /* For non-empty files check the mtime */
-                return timespec_load(&st.st_mtim) != mtime;
+                return timespec_load(&st.st_mtim) > mtime;
         else if (!null_or_empty(&st))
                 /* For masked files check if they are still so */
                 return true;
@@ -2974,32 +2968,24 @@ static bool fragment_mtime_changed(const char *path, usec_t mtime) {
 bool unit_need_daemon_reload(Unit *u) {
         _cleanup_strv_free_ char **t = NULL;
         char **path;
-        unsigned loaded_cnt, current_cnt;
 
         assert(u);
 
-        if (fragment_mtime_changed(u->fragment_path, u->fragment_mtime) ||
-            fragment_mtime_changed(u->source_path, u->source_mtime))
+        if (fragment_mtime_newer(u->fragment_path, u->fragment_mtime))
                 return true;
 
-        (void) unit_find_dropin_paths(u, &t);
-        loaded_cnt = strv_length(t);
-        current_cnt = strv_length(u->dropin_paths);
-
-        if (loaded_cnt == current_cnt) {
-                if (loaded_cnt == 0)
-                        return false;
+        if (fragment_mtime_newer(u->source_path, u->source_mtime))
+                return true;
 
-                if (strv_overlap(u->dropin_paths, t)) {
-                        STRV_FOREACH(path, u->dropin_paths)
-                                if (fragment_mtime_changed(*path, u->dropin_mtime))
-                                        return true;
+        (void) unit_find_dropin_paths(u, &t);
+        if (!strv_equal(u->dropin_paths, t))
+                return true;
 
-                        return false;
-                }
-        }
+        STRV_FOREACH(path, u->dropin_paths)
+                if (fragment_mtime_newer(*path, u->dropin_mtime))
+                        return true;
 
-        return true;
+        return false;
 }
 
 void unit_reset_failed(Unit *u) {
diff --git a/src/core/unit.h b/src/core/unit.h
index be62e88421..f14972728e 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -611,6 +611,8 @@ static inline bool unit_supported(Unit *u) {
 void unit_warn_if_dir_nonempty(Unit *u, const char* where);
 int unit_fail_if_symlink(Unit *u, const char* where);
 
+int unit_start_limit_test(Unit *u);
+
 /* Macros which append UNIT= or USER_UNIT= to the message */
 
 #define log_unit_full(unit, level, error, ...)                          \