udev: fix performance regression in resolving event dependencies (#40364)

Fixes #39583.
Fixes #39817.

.github/workflows/coverage.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
-      - uses: systemd/mkosi@e3642f81d3a7f8f9310c0c734b2ba9dd41e50e14
+      - uses: systemd/mkosi@14d2d37a1923c03062f55454b2b61d0c64db6238
 
       # Freeing up disk space with rm -rf can take multiple minutes. Since we don't need the extra free space
       # immediately, we remove the files in the background. However, we first move them to a different location

.github/workflows/linter.yml

@@ -39,7 +39,7 @@ jobs:
           GITHUB_ACTIONS_CONFIG_FILE: actionlint.yml
           ENABLE_GITHUB_PULL_REQUEST_SUMMARY_COMMENT: false
 
-      - uses: systemd/mkosi@e3642f81d3a7f8f9310c0c734b2ba9dd41e50e14
+      - uses: systemd/mkosi@14d2d37a1923c03062f55454b2b61d0c64db6238
 
       - name: Check that tabs are not used in Python code
         run: sh -c '! git grep -P "\\t" -- src/core/generate-bpf-delegate-configs.py src/boot/generate-hwids-section.py src/ukify/ukify.py test/integration-tests/integration-test-wrapper.py'

.github/workflows/mkosi.yml

@@ -167,7 +167,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
-      - uses: systemd/mkosi@e3642f81d3a7f8f9310c0c734b2ba9dd41e50e14
+      - uses: systemd/mkosi@14d2d37a1923c03062f55454b2b61d0c64db6238
 
       # Freeing up disk space with rm -rf can take multiple minutes. Since we don't need the extra free space
       # immediately, we remove the files in the background. However, we first move them to a different location

man/systemd-sleep.conf.xml

@@ -96,12 +96,13 @@
           <para>If the system has no battery, it would be hibernated after <varname>HibernateDelaySec=</varname>
           has passed. If not set, then defaults to <literal>2h</literal>.</para>
 
-          <para>If the system has battery and <varname>HibernateDelaySec=</varname> is not set, low-battery
+          <para>If the system has battery, low-battery alarms (ACPI _BTP) are tried first for detecting
-          alarms (ACPI _BTP) are tried first for detecting battery percentage and wake up the system for hibernation.
+          battery percentage and wake up the system for hibernation. If <varname>HibernateDelaySec=</varname>
-          If not available, or <varname>HibernateDelaySec=</varname> is set, the system would regularly wake
+          is also set, an additional timer is configured so that the system hibernates on whichever comes
-          up to check the time and detect the battery percentage/discharging rate. The rate is used to
+          first: low battery or the configured delay. If ACPI _BTP is not available, the system would
-          schedule the next detection. If that is also not available, <varname>SuspendEstimationSec=</varname>
+          regularly wake up to check the time and detect the battery percentage/discharging rate. The rate
-          is used as last resort.</para>
+          is used to schedule the next detection. If that is also not available,
+          <varname>SuspendEstimationSec=</varname> is used as last resort.</para>
 
           <xi:include href="version-info.xml" xpointer="v239"/>
         </listitem>

mkosi/mkosi.conf

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
 [Config]
-MinimumVersion=commit:e3642f81d3a7f8f9310c0c734b2ba9dd41e50e14
+MinimumVersion=commit:14d2d37a1923c03062f55454b2b61d0c64db6238
 Dependencies=
         initrd
         minimal-base

src/core/job.c

@@ -787,7 +787,7 @@ static void job_emit_done_message(Unit *u, uint32_t job_id, JobType t, JobResult
                                 log_unit_struct(
                                         u,
                                         job_done_messages[result].log_level,
-                                        LOG_MESSAGE("%s was skipped because no trigger condition checks were met.",
+                                        LOG_MESSAGE("%s skipped, no trigger condition checks were met.",
                                                     ident),
                                         LOG_ITEM("JOB_ID=%" PRIu32, job_id),
                                         LOG_ITEM("JOB_TYPE=%s", job_type_to_string(t)),
@@ -798,7 +798,7 @@ static void job_emit_done_message(Unit *u, uint32_t job_id, JobType t, JobResult
                                 log_unit_struct(
                                         u,
                                         job_done_messages[result].log_level,
-                                        LOG_MESSAGE("%s was skipped because of an unmet condition check (%s=%s%s).",
+                                        LOG_MESSAGE("%s skipped, unmet condition check %s=%s%s",
                                                     ident,
                                                     condition_type_to_string(c->type),
                                                     c->negate ? "!" : "",

src/report/report.c

@@ -79,16 +79,13 @@ static int metrics_on_query_reply(
                         log_info("Varlink timed out");
                 else
                         log_error("Varlink error: %s", error_id);
-
+        } else {
-                goto finish;
-        }
-
                 /* Collect metrics for later sorting */
                 if (!GREEDY_REALLOC(context->metrics, context->n_metrics + 1))
                         return log_oom();
                 context->metrics[context->n_metrics++] = sd_json_variant_ref(parameters);
+        }
 
-finish:
         if (!FLAGS_SET(flags, SD_VARLINK_REPLY_CONTINUES)) {
                 assert(context->n_open_connections > 0);
                 context->n_open_connections--;
@@ -111,7 +108,7 @@ static int metrics_call(const char *path, sd_event *event, sd_varlink **ret, Con
 
         r = sd_varlink_connect_address(&vl, path);
         if (r < 0)
-                return log_debug_errno(r, "Unable to connect to %s: %m", path);
+                return log_error_errno(r, "Unable to connect to %s: %m", path);
 
         (void) sd_varlink_set_userdata(vl, context);
 
@@ -121,15 +118,15 @@ static int metrics_call(const char *path, sd_event *event, sd_varlink **ret, Con
 
         r = sd_varlink_attach_event(vl, event, SD_EVENT_PRIORITY_NORMAL);
         if (r < 0)
-                return log_debug_errno(r, "Failed to attach varlink connection to event loop: %m");
+                return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");
 
         r = sd_varlink_bind_reply(vl, metrics_on_query_reply);
         if (r < 0)
-                return log_debug_errno(r, "Failed to bind reply callback: %m");
+                return log_error_errno(r, "Failed to bind reply callback: %m");
 
         r = sd_varlink_observe(vl, "io.systemd.Metrics.List", /* parameters= */ NULL);
         if (r < 0)
-                return log_debug_errno(r, "Failed to issue io.systemd.Metrics.List call: %m");
+                return log_error_errno(r, "Failed to issue io.systemd.Metrics.List call: %m");
 
         *ret = TAKE_PTR(vl);
 
@@ -156,9 +153,6 @@ static void context_done(Context *context) {
 static void metrics_output_sorted(Context *context) {
         assert(context);
 
-        if (context->n_metrics == 0)
-                return;
-
         typesafe_qsort(context->metrics, context->n_metrics, metric_compare);
 
         FOREACH_ARRAY(m, context->metrics, context->n_metrics)
@@ -167,26 +161,27 @@ static void metrics_output_sorted(Context *context) {
                                 SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO | SD_JSON_FORMAT_FLUSH,
                                 stdout,
                                 NULL);
+
+        if (context->n_metrics == 0)
+                log_warning("No reporting sockets found.");
 }
 
 static int metrics_query(void) {
-        _cleanup_closedir_ DIR *d = NULL;
-        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
-        _cleanup_free_ char *metrics_path = NULL;
         int r;
 
+        _cleanup_free_ char *metrics_path = NULL;
         r = runtime_directory_generic(arg_runtime_scope, "systemd/report", &metrics_path);
         if (r < 0)
                 return log_error_errno(r, "Failed to determine metrics directory path: %m");
 
-        d = opendir(metrics_path);
+        log_debug("Looking for reports in %s/", metrics_path);
-        if (!d) {
-                if (errno == ENOENT)
-                        return 0;
 
-                return log_error_errno(errno, "Failed to open directory %s: %m", metrics_path);
+        _cleanup_closedir_ DIR *d = opendir(metrics_path);
-        }
+        if (!d)
+                return log_full_errno(errno == ENOENT ? LOG_WARNING : LOG_ERR, errno,
+                                      "Failed to open metrics directory %s: %m", metrics_path);
 
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
         r = sd_event_default(&event);
         if (r < 0)
                 return log_error_errno(r, "Failed to get event loop: %m");
@@ -198,27 +193,25 @@ static int metrics_query(void) {
         size_t n_varlinks = MAX_CONCURRENT_METRICS_SOCKETS;
         sd_varlink **varlinks = new0(sd_varlink *, n_varlinks);
         if (!varlinks)
-                return log_error_errno(ENOMEM, "Failed to allocate varlinks array: %m");
+                return log_oom();
 
         CLEANUP_ARRAY(varlinks, n_varlinks, sd_varlink_unref_many);
 
-        Context context = {};
+        _cleanup_(context_done) Context context = {};
 
-        FOREACH_DIRENT(de, d, return -errno) {
+        FOREACH_DIRENT(de, d,
-                _cleanup_free_ char *p = NULL;
+                       return log_warning_errno(errno, "Failed to read %s: %m", metrics_path)) {
 
                 if (!IN_SET(de->d_type, DT_SOCK, DT_UNKNOWN))
                         continue;
 
-                p = path_join(metrics_path, de->d_name);
+                _cleanup_free_ char *p = path_join(metrics_path, de->d_name);
                 if (!p)
                         return log_oom();
 
                 r = metrics_call(p, event, &varlinks[context.n_open_connections], &context);
-                if (r < 0) {
+                if (r < 0)
-                        log_error_errno(r, "Failed to connect to %s: %m", p);
                         continue;
-                }
 
                 if (++context.n_open_connections >= MAX_CONCURRENT_METRICS_SOCKETS) {
                         log_warning("Too many concurrent metrics sockets, stop iterating");
@@ -226,16 +219,14 @@ static int metrics_query(void) {
                 }
         }
 
+        if (context.n_open_connections > 0) {
                 r = sd_event_loop(event);
-        if (r < 0) {
+                if (r < 0)
-                context_done(&context);
                         return log_error_errno(r, "Failed to run event loop: %m");
         }
 
         metrics_output_sorted(&context);
 
-        context_done(&context);
-
         return 0;
 }
 
@@ -318,11 +309,7 @@ static int run(int argc, char *argv[]) {
         if (r <= 0)
                 return r;
 
-        r = metrics_query();
+        return metrics_query();
-        if (r < 0)
-                return r;
-
-        return 0;
 }
 
 DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(run);

src/sleep/sleep.c

@@ -507,13 +507,14 @@ static int custom_timer_suspend(const SleepConfig *sleep_config) {
 }
 
 static int execute_s2h(const SleepConfig *sleep_config) {
+        _cleanup_close_ int tfd = -EBADF;
+        usec_t hibernate_timestamp = 0;
         int r;
 
         assert(sleep_config);
 
-        /* Only check if we have automated battery alarms if HibernateDelaySec= is not set, as in that case
+        /* Always check if we have automated battery alarms, regardless of HibernateDelaySec= setting.
-         * we'll busy poll for the configured interval instead */
+         * This allows both low-battery hibernation AND timeout-based hibernation to work together. */
-        if (!timestamp_is_set(sleep_config->hibernate_delay_usec)) {
         r = check_wakeup_type();
         if (r < 0)
                 log_warning_errno(r, "Failed to check hardware wakeup type, ignoring: %m");
@@ -522,10 +523,41 @@ static int execute_s2h(const SleepConfig *sleep_config) {
                 if (r < 0)
                         log_warning_errno(r, "Failed to check whether acpi_btp support is enabled or not, ignoring: %m");
         }
-        } else
-                r = 0;  /* Force fallback path */
 
-        if (r > 0) { /* If we have both wakeup alarms and battery trip point support, use them */
+        if (r > 0) {
+                /* We have hardware battery alarm support (ACPI _BTP). If HibernateDelaySec= is also set,
+                 * set up an RTC alarm so we hibernate on whichever comes first: low battery or timeout. */
+                if (timestamp_is_set(sleep_config->hibernate_delay_usec)) {
+                        tfd = timerfd_create(CLOCK_BOOTTIME_ALARM, TFD_NONBLOCK|TFD_CLOEXEC);
+                        if (tfd < 0)
+                                return log_error_errno(errno, "Error creating timerfd: %m");
+
+                        hibernate_timestamp = usec_add(now(CLOCK_BOOTTIME), sleep_config->hibernate_delay_usec);
+                }
+
+                for (;;) {
+                        if (tfd >= 0) {
+                                struct itimerspec ts = {};
+                                usec_t time_left;
+
+                                /* Handle HibernateOnACPower=no: reset timer while on AC power */
+                                if (!sleep_config->hibernate_on_ac_power && on_ac_power() > 0) {
+                                        log_debug("On AC power with HibernateOnACPower=no, resetting hibernate timer");
+                                        hibernate_timestamp = usec_add(now(CLOCK_BOOTTIME), sleep_config->hibernate_delay_usec);
+                                }
+
+                                time_left = usec_sub_unsigned(hibernate_timestamp, now(CLOCK_BOOTTIME));
+                                if (time_left <= 0)
+                                        break; /* Timer expired, hibernate */
+
+                                log_debug("Set timerfd wake alarm for %s",
+                                          FORMAT_TIMESPAN(time_left, USEC_PER_SEC));
+                                timespec_store(&ts.it_value, time_left);
+
+                                if (timerfd_settime(tfd, 0, &ts, NULL) < 0)
+                                        return log_error_errno(errno, "Error setting hibernate delay timer: %m");
+                        }
+
                         log_debug("Attempting to suspend...");
                         r = execute(sleep_config, SLEEP_SUSPEND, NULL);
                         if (r < 0)
@@ -534,10 +566,31 @@ static int execute_s2h(const SleepConfig *sleep_config) {
                         r = check_wakeup_type();
                         if (r < 0)
                                 return log_error_errno(r, "Failed to check hardware wakeup type: %m");
+                        if (r > 0) {
+                                /* APM Timer wakeup - this means the battery alarm triggered, hibernate */
+                                log_debug("Woken by APM Timer (battery low), proceeding to hibernate");
+                                break;
+                        }
 
-                if (r == 0)
+                        if (tfd >= 0) {
-                        /* For APM Timer wakeup, system should hibernate else wakeup */
+                                /* Check if our HibernateDelaySec timer fired */
+                                r = fd_wait_for_event(tfd, POLLIN, 0);
+                                if (r < 0)
+                                        return log_error_errno(r, "Error polling timerfd: %m");
+                                if (FLAGS_SET(r, POLLIN)) {
+                                        /* Timer fired - but respect HibernateOnACPower setting */
+                                        if (!sleep_config->hibernate_on_ac_power && on_ac_power() > 0) {
+                                                log_debug("Timer fired but on AC power with HibernateOnACPower=no, continuing suspend");
+                                                continue;
+                                        }
+                                        log_debug("HibernateDelaySec timeout reached, proceeding to hibernate");
+                                        break;
+                                }
+                        }
+
+                        /* Manual wakeup - not battery alarm and not timer */
                         return 0;
+                }
         } else {
                 r = custom_timer_suspend(sleep_config);
                 if (r < 0)

src/udev/udev-manager.c

@@ -53,9 +53,14 @@ typedef enum EventState {
         EVENT_QUEUED,
         EVENT_RUNNING,
         EVENT_LOCKED,
+        EVENT_PROCESSED,
 } EventState;
 
 typedef struct Event {
+        /* All events that have not been processed (state != EVENT_PROCESSED) are referenced by the Manager.
+         * Additionally, an event may be referenced by events blocked by this event. See event_find_blocker(). */
+        unsigned n_ref;
+
         Manager *manager;
         Worker *worker;
         EventState state;
@@ -76,9 +81,8 @@ typedef struct Event {
         char *whole_disk;
         LIST_FIELDS(Event, same_disk);
 
-        bool dependencies_built;
+        /* The last blocker for this event. This event must not be processed before the blocker is processed. */
-        Set *blocker_events;
+        Event *blocker;
-        Set *blocking_events;
 
         LIST_FIELDS(Event, event);
 } Event;
@@ -101,21 +105,6 @@ typedef struct Worker {
         Event *event;
 } Worker;
 
-static void event_clear_dependencies(Event *event) {
-        assert(event);
-
-        Event *e;
-        while ((e = set_steal_first(event->blocker_events)))
-                assert_se(set_remove(e->blocking_events, event) == event);
-        event->blocker_events = set_free(event->blocker_events);
-
-        while ((e = set_steal_first(event->blocking_events)))
-                assert_se(set_remove(e->blocker_events, event) == event);
-        event->blocking_events = set_free(event->blocking_events);
-
-        event->dependencies_built = false;
-}
-
 static void event_unset_whole_disk(Event *event) {
         Manager *manager = ASSERT_PTR(ASSERT_PTR(event)->manager);
 
@@ -140,6 +129,10 @@ static void event_unset_whole_disk(Event *event) {
         event->whole_disk = mfree(event->whole_disk);
 }
 
+static Event* event_free(Event *event);
+DEFINE_PRIVATE_TRIVIAL_REF_UNREF_FUNC(Event, event, event_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC(Event*, event_unref);
+
 static Event* event_free(Event *event) {
         if (!event)
                 return NULL;
@@ -156,14 +149,25 @@ static Event* event_free(Event *event) {
         if (event->worker)
                 event->worker->event = NULL;
 
-        event_clear_dependencies(event);
+        event_unref(event->blocker);
 
         sd_device_unref(event->dev);
 
         return mfree(event);
 }
 
-DEFINE_TRIVIAL_CLEANUP_FUNC(Event*, event_free);
+static Event* event_enter_processed(Event *event) {
+        if (!event)
+                return NULL;
+
+        if (event->state == EVENT_PROCESSED)
+                return NULL;
+
+        event->state = EVENT_PROCESSED;
+        return event_unref(event);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(Event*, event_enter_processed);
 
 static Worker* worker_free(Worker *worker) {
         if (!worker)
@@ -176,7 +180,6 @@ static Worker* worker_free(Worker *worker) {
         sd_event_source_unref(worker->timeout_warning_event_source);
         sd_event_source_unref(worker->timeout_kill_event_source);
         pidref_done(&worker->pidref);
-        event_free(worker->event);
 
         return mfree(worker);
 }
@@ -200,8 +203,8 @@ Manager* manager_free(Manager *manager) {
         udev_rules_free(manager->rules);
 
         hashmap_free(manager->workers);
-        while (manager->events)
+        LIST_FOREACH(event, event, manager->events)
-                event_free(manager->events);
+                event_enter_processed(event);
 
         prioq_free(manager->locked_events_by_time);
         hashmap_free(manager->locked_events_by_disk);
@@ -392,9 +395,85 @@ void manager_revert(Manager *manager) {
         manager_kill_workers(manager, SIGTERM);
 }
 
+static int on_worker_timeout_kill(sd_event_source *s, uint64_t usec, void *userdata) {
+        Worker *worker = ASSERT_PTR(userdata);
+        Manager *manager = ASSERT_PTR(worker->manager);
+        Event *event = ASSERT_PTR(worker->event);
+
+        (void) pidref_kill_and_sigcont(&worker->pidref, manager->config.timeout_signal);
+        worker->state = WORKER_KILLED;
+
+        log_device_error(event->dev, "Worker ["PID_FMT"] processing SEQNUM=%"PRIu64" killed.", worker->pidref.pid, event->seqnum);
+        return 0;
+}
+
+static int on_worker_timeout_warning(sd_event_source *s, uint64_t usec, void *userdata) {
+        Worker *worker = ASSERT_PTR(userdata);
+        Event *event = ASSERT_PTR(worker->event);
+
+        log_device_warning(event->dev, "Worker ["PID_FMT"] processing SEQNUM=%"PRIu64" is taking a long time.", worker->pidref.pid, event->seqnum);
+        return 0;
+}
+
+static void worker_attach_event(Worker *worker, Event *event) {
+        Manager *manager = ASSERT_PTR(ASSERT_PTR(worker)->manager);
+
+        assert(event);
+        assert(event->state == EVENT_QUEUED);
+        assert(!event->worker);
+        assert(IN_SET(worker->state, WORKER_UNDEF, WORKER_IDLE));
+        assert(!worker->event);
+
+        worker->state = WORKER_RUNNING;
+        worker->event = event;
+        event->state = EVENT_RUNNING;
+        event->worker = worker;
+
+        (void) event_reset_time_relative(
+                        manager->event,
+                        &worker->timeout_warning_event_source,
+                        CLOCK_MONOTONIC,
+                        udev_warn_timeout(manager->config.timeout_usec),
+                        USEC_PER_SEC,
+                        on_worker_timeout_warning,
+                        worker,
+                        EVENT_PRIORITY_WORKER_TIMER,
+                        "worker-timeout-warn",
+                        /* force_reset= */ true);
+
+        (void) event_reset_time_relative(
+                        manager->event,
+                        &worker->timeout_kill_event_source,
+                        CLOCK_MONOTONIC,
+                        manager_kill_worker_timeout(manager),
+                        USEC_PER_SEC,
+                        on_worker_timeout_kill,
+                        worker,
+                        EVENT_PRIORITY_WORKER_TIMER,
+                        "worker-timeout-kill",
+                        /* force_reset= */ true);
+}
+
+static Event* worker_detach_event(Worker *worker) {
+        assert(worker);
+
+        Event *event = TAKE_PTR(worker->event);
+        if (event)
+                assert_se(TAKE_PTR(event->worker) == worker);
+
+        if (worker->state != WORKER_KILLED)
+                worker->state = WORKER_IDLE;
+
+        (void) event_source_disable(worker->timeout_warning_event_source);
+        (void) event_source_disable(worker->timeout_kill_event_source);
+
+        return event;
+}
+
 static int on_worker_exit(sd_event_source *s, const siginfo_t *si, void *userdata) {
         _cleanup_(worker_freep) Worker *worker = ASSERT_PTR(userdata);
-        sd_device *dev = worker->event ? ASSERT_PTR(worker->event->dev) : NULL;
+        _cleanup_(event_enter_processedp) Event *event = worker_detach_event(worker);
+        sd_device *dev = event ? ASSERT_PTR(event->dev) : NULL;
 
         assert(si);
 
@@ -472,81 +551,6 @@ static int worker_new(Worker **ret, Manager *manager, sd_device_monitor *worker_
         return 0;
 }
 
-static int on_worker_timeout_kill(sd_event_source *s, uint64_t usec, void *userdata) {
-        Worker *worker = ASSERT_PTR(userdata);
-        Manager *manager = ASSERT_PTR(worker->manager);
-        Event *event = ASSERT_PTR(worker->event);
-
-        (void) pidref_kill_and_sigcont(&worker->pidref, manager->config.timeout_signal);
-        worker->state = WORKER_KILLED;
-
-        log_device_error(event->dev, "Worker ["PID_FMT"] processing SEQNUM=%"PRIu64" killed.", worker->pidref.pid, event->seqnum);
-        return 0;
-}
-
-static int on_worker_timeout_warning(sd_event_source *s, uint64_t usec, void *userdata) {
-        Worker *worker = ASSERT_PTR(userdata);
-        Event *event = ASSERT_PTR(worker->event);
-
-        log_device_warning(event->dev, "Worker ["PID_FMT"] processing SEQNUM=%"PRIu64" is taking a long time.", worker->pidref.pid, event->seqnum);
-        return 0;
-}
-
-static void worker_attach_event(Worker *worker, Event *event) {
-        Manager *manager = ASSERT_PTR(ASSERT_PTR(worker)->manager);
-
-        assert(event);
-        assert(event->state == EVENT_QUEUED);
-        assert(!event->worker);
-        assert(IN_SET(worker->state, WORKER_UNDEF, WORKER_IDLE));
-        assert(!worker->event);
-
-        worker->state = WORKER_RUNNING;
-        worker->event = event;
-        event->state = EVENT_RUNNING;
-        event->worker = worker;
-
-        (void) event_reset_time_relative(
-                        manager->event,
-                        &worker->timeout_warning_event_source,
-                        CLOCK_MONOTONIC,
-                        udev_warn_timeout(manager->config.timeout_usec),
-                        USEC_PER_SEC,
-                        on_worker_timeout_warning,
-                        worker,
-                        EVENT_PRIORITY_WORKER_TIMER,
-                        "worker-timeout-warn",
-                        /* force_reset= */ true);
-
-        (void) event_reset_time_relative(
-                        manager->event,
-                        &worker->timeout_kill_event_source,
-                        CLOCK_MONOTONIC,
-                        manager_kill_worker_timeout(manager),
-                        USEC_PER_SEC,
-                        on_worker_timeout_kill,
-                        worker,
-                        EVENT_PRIORITY_WORKER_TIMER,
-                        "worker-timeout-kill",
-                        /* force_reset= */ true);
-}
-
-static Event* worker_detach_event(Worker *worker) {
-        assert(worker);
-
-        Event *event = TAKE_PTR(worker->event);
-        if (event)
-                assert_se(TAKE_PTR(event->worker) == worker);
-
-        if (worker->state != WORKER_KILLED)
-                worker->state = WORKER_IDLE;
-
-        (void) event_source_disable(worker->timeout_warning_event_source);
-        (void) event_source_disable(worker->timeout_kill_event_source);
-
-        return event;
-}
-
 static int worker_spawn(Manager *manager, Event *event) {
         int r;
 
@@ -649,17 +653,21 @@ bool devpath_conflict(const char *a, const char *b) {
         return *a == '/' || *b == '/' || *a == *b;
 }
 
-static int event_build_dependencies(Event *event) {
+static void event_find_blocker(Event *event) {
-        int r;
-
         assert(event);
 
         /* lookup event for identical, parent, child device */
 
-        if (event->dependencies_built)
+        if (event->blocker && event->blocker->state != EVENT_PROCESSED)
-                return 0;
+                /* Previously found blocker is not processed yet. */
+                return;
+
+        /* If we have not found blocker yet, or the previously found blocker has been processed, let's find
+         * (another) blocker for this event. */
+        LIST_FOREACH_BACKWARDS(event, e, (event->blocker ?: event)->event_prev) {
+                if (e->state == EVENT_PROCESSED)
+                        continue;
 
-        LIST_FOREACH_BACKWARDS(event, e, event->event_prev) {
                 if (!streq_ptr(event->id, e->id) &&
                     !devpath_conflict(event->devpath, e->devpath) &&
                     !devpath_conflict(event->devpath, e->devpath_old) &&
@@ -667,22 +675,16 @@ static int event_build_dependencies(Event *event) {
                     !(event->devnode && streq_ptr(event->devnode, e->devnode)))
                         continue;
 
-                r = set_ensure_put(&event->blocker_events, NULL, e);
-                if (r < 0)
-                        return r;
-
-                r = set_ensure_put(&e->blocking_events, NULL, event);
-                if (r < 0) {
-                        assert_se(set_remove(event->blocker_events, e) == e);
-                        return r;
-                }
-
                 log_device_debug(event->dev, "SEQNUM=%" PRIu64 " blocked by SEQNUM=%" PRIu64,
                                  event->seqnum, e->seqnum);
+
+                unref_and_replace_full(event->blocker, e, event_ref, event_unref);
+                return;
         }
 
-        event->dependencies_built = true;
+        /* No new blocker is found, and if set, previously found blocker has been processed. Clear the
-        return 0;
+         * previous blocker if set. */
+        event->blocker = event_unref(event->blocker);
 }
 
 static bool manager_can_process_event(Manager *manager) {
@@ -739,14 +741,10 @@ static int event_queue_start(Manager *manager) {
                 if (event->state != EVENT_QUEUED)
                         continue;
 
-                r = event_build_dependencies(event);
+                event_find_blocker(event);
-                if (r < 0)
-                        log_device_warning_errno(event->dev, r,
-                                                 "Failed to check dependencies for event (SEQNUM=%"PRIu64", ACTION=%s), ignoring: %m",
-                                                 event->seqnum, strna(device_action_to_string(event->action)));
 
                 /* do not start event if parent or child event is still running or queued */
-                if (!set_isempty(event->blocker_events))
+                if (event->blocker)
                         continue;
 
                 r = event_run(event);
@@ -927,11 +925,12 @@ static int event_queue_insert(Manager *manager, sd_device *dev) {
         if (r < 0 && r != -ENOENT)
                 return r;
 
-        _cleanup_(event_freep) Event *event = new(Event, 1);
+        _cleanup_(event_unrefp) Event *event = new(Event, 1);
         if (!event)
                 return -ENOMEM;
 
         *event = (Event) {
+                .n_ref = 1,
                 .dev = sd_device_ref(dev),
                 .seqnum = seqnum,
                 .action = action,
@@ -943,6 +942,9 @@ static int event_queue_insert(Manager *manager, sd_device *dev) {
                 .locked_event_prioq_index = PRIOQ_IDX_NULL,
         };
 
+        /* The kernel sometimes sends events in a wrong order, and we may receive an event with smaller
+         * SEQNUM after one with larger SEQNUM. To workaround the issue, let's reorder events if necessary. */
+
         Event *prev = NULL;
         LIST_FOREACH_BACKWARDS(event, e, manager->last_event) {
                 if (e->seqnum < event->seqnum) {
@@ -954,8 +956,9 @@ static int event_queue_insert(Manager *manager, sd_device *dev) {
                                                         "The event (SEQNUM=%"PRIu64") has been already queued.",
                                                         event->seqnum);
 
-                /* Inserting an event in an earlier place may change dependency tree. Let's rebuild it later. */
+                /* The inserted event may be a blocker of an already queued event, hence the already found
-                event_clear_dependencies(e);
+                 * blocker may not be the last one. Let's find the last blocker again later. */
+                e->blocker = event_unref(e->blocker);
         }
 
         LIST_INSERT_AFTER(event, manager->events, prev, event);
@@ -1211,7 +1214,7 @@ static int on_worker_notify(sd_event_source *s, int fd, uint32_t revents, void *
                 return 0;
         }
 
-        _cleanup_(event_freep) Event *event = worker_detach_event(worker);
+        _cleanup_(event_enter_processedp) Event *event = worker_detach_event(worker);
 
         if (strv_contains(l, "TRY_AGAIN=1")) {
                 /* Worker cannot lock the device. */

tools/fetch-mkosi.py

@@ -43,7 +43,7 @@ def read_config():
 
 def commit_file(files: list[Path], commit: str, changes: str):
     message = '\n'.join((
-        f'mkosi: update mkosi commit reference to {commit}',
+        f'mkosi: update mkosi ref to {commit}',
         '',
         changes))