unit.c 47.9 KB
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/*-*- Mode: C; c-basic-offset: 8 -*-*/

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/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

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#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/timerfd.h>
#include <sys/poll.h>
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#include <stdlib.h>
#include <unistd.h>
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#include "set.h"
#include "unit.h"
#include "macro.h"
#include "strv.h"
#include "load-fragment.h"
#include "load-dropin.h"
#include "log.h"
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#include "unit-name.h"
#include "specifier.h"
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const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
        [UNIT_SERVICE] = &service_vtable,
        [UNIT_TIMER] = &timer_vtable,
        [UNIT_SOCKET] = &socket_vtable,
        [UNIT_TARGET] = &target_vtable,
        [UNIT_DEVICE] = &device_vtable,
        [UNIT_MOUNT] = &mount_vtable,
        [UNIT_AUTOMOUNT] = &automount_vtable,
        [UNIT_SNAPSHOT] = &snapshot_vtable
};

Unit *unit_new(Manager *m) {
        Unit *u;

        assert(m);

        if (!(u = new0(Unit, 1)))
                return NULL;

        if (!(u->meta.names = set_new(string_hash_func, string_compare_func))) {
                free(u);
                return NULL;
        }

        u->meta.manager = m;
        u->meta.type = _UNIT_TYPE_INVALID;

        return u;
}

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bool unit_has_name(Unit *u, const char *name) {
        assert(u);
        assert(name);

        return !!set_get(u->meta.names, (char*) name);
}

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int unit_add_name(Unit *u, const char *text) {
        UnitType t;
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        char *s = NULL, *i = NULL;
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        int r;

        assert(u);
        assert(text);

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        if (unit_name_is_template(text)) {
                if (!u->meta.instance)
                        return -EINVAL;
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                s = unit_name_replace_instance(text, u->meta.instance);
        } else
                s = strdup(text);
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        if (!s)
                return -ENOMEM;
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        if (!unit_name_is_valid(s)) {
                r = -EINVAL;
                goto fail;
        }
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        assert_se((t = unit_name_to_type(s)) >= 0);
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        if (u->meta.type != _UNIT_TYPE_INVALID && t != u->meta.type) {
                r = -EINVAL;
                goto fail;
        }
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        if ((r = unit_name_to_instance(s, &i)) < 0)
                goto fail;
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        if (i && unit_vtable[t]->no_instances)
                goto fail;

        if (u->meta.type != _UNIT_TYPE_INVALID && !streq_ptr(u->meta.instance, i)) {
                r = -EINVAL;
                goto fail;
        }

        if (unit_vtable[t]->no_alias &&
            !set_isempty(u->meta.names) &&
            !set_get(u->meta.names, s)) {
                r = -EEXIST;
                goto fail;
        }

        if ((r = set_put(u->meta.names, s)) < 0) {
                if (r == -EEXIST)
                        r = 0;
                goto fail;
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        }

        if ((r = hashmap_put(u->meta.manager->units, s, u)) < 0) {
                set_remove(u->meta.names, s);
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                goto fail;
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        }

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        if (u->meta.type == _UNIT_TYPE_INVALID) {
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                u->meta.type = t;
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                u->meta.id = s;
                u->meta.instance = i;

                LIST_PREPEND(Meta, units_per_type, u->meta.manager->units_per_type[t], &u->meta);
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                if (UNIT_VTABLE(u)->init)
                        UNIT_VTABLE(u)->init(u);
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        } else
                free(i);
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        unit_add_to_dbus_queue(u);
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        return 0;
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fail:
        free(s);
        free(i);

        return r;
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}

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int unit_choose_id(Unit *u, const char *name) {
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        char *s, *t = NULL;
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        assert(u);
        assert(name);

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        if (unit_name_is_template(name)) {

                if (!u->meta.instance)
                        return -EINVAL;

                if (!(t = unit_name_replace_instance(name, u->meta.instance)))
                        return -ENOMEM;

                name = t;
        }

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        /* Selects one of the names of this unit as the id */
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        s = set_get(u->meta.names, (char*) name);
        free(t);
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        if (!s)
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                return -ENOENT;

        u->meta.id = s;
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        unit_add_to_dbus_queue(u);
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        return 0;
}

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int unit_set_description(Unit *u, const char *description) {
        char *s;

        assert(u);

        if (!(s = strdup(description)))
                return -ENOMEM;

        free(u->meta.description);
        u->meta.description = s;
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        unit_add_to_dbus_queue(u);
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        return 0;
}

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void unit_add_to_load_queue(Unit *u) {
        assert(u);
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        assert(u->meta.type != _UNIT_TYPE_INVALID);
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        if (u->meta.load_state != UNIT_STUB || u->meta.in_load_queue)
                return;

        LIST_PREPEND(Meta, load_queue, u->meta.manager->load_queue, &u->meta);
        u->meta.in_load_queue = true;
}

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void unit_add_to_cleanup_queue(Unit *u) {
        assert(u);

        if (u->meta.in_cleanup_queue)
                return;

        LIST_PREPEND(Meta, cleanup_queue, u->meta.manager->cleanup_queue, &u->meta);
        u->meta.in_cleanup_queue = true;
}

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void unit_add_to_dbus_queue(Unit *u) {
        assert(u);
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        assert(u->meta.type != _UNIT_TYPE_INVALID);
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        if (u->meta.load_state == UNIT_STUB || u->meta.in_dbus_queue || set_isempty(u->meta.manager->subscribed))
                return;

        LIST_PREPEND(Meta, dbus_queue, u->meta.manager->dbus_unit_queue, &u->meta);
        u->meta.in_dbus_queue = true;
}

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static void bidi_set_free(Unit *u, Set *s) {
        Iterator i;
        Unit *other;

        assert(u);

        /* Frees the set and makes sure we are dropped from the
         * inverse pointers */

        SET_FOREACH(other, s, i) {
                UnitDependency d;

                for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
                        set_remove(other->meta.dependencies[d], u);
        }

        set_free(s);
}

void unit_free(Unit *u) {
        UnitDependency d;
        Iterator i;
        char *t;

        assert(u);

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        bus_unit_send_removed_signal(u);

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        /* Detach from next 'bigger' objects */
        SET_FOREACH(t, u->meta.names, i)
                hashmap_remove_value(u->meta.manager->units, t, u);

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        if (u->meta.type != _UNIT_TYPE_INVALID)
                LIST_REMOVE(Meta, units_per_type, u->meta.manager->units_per_type[u->meta.type], &u->meta);

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        if (u->meta.in_load_queue)
                LIST_REMOVE(Meta, load_queue, u->meta.manager->load_queue, &u->meta);

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        if (u->meta.in_dbus_queue)
                LIST_REMOVE(Meta, dbus_queue, u->meta.manager->dbus_unit_queue, &u->meta);

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        if (u->meta.in_cleanup_queue)
                LIST_REMOVE(Meta, cleanup_queue, u->meta.manager->cleanup_queue, &u->meta);

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        /* Free data and next 'smaller' objects */
        if (u->meta.job)
                job_free(u->meta.job);

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        if (u->meta.load_state != UNIT_STUB)
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                if (UNIT_VTABLE(u)->done)
                        UNIT_VTABLE(u)->done(u);

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        cgroup_bonding_free_list(u->meta.cgroup_bondings);
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        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
                bidi_set_free(u, u->meta.dependencies[d]);

        free(u->meta.description);
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        free(u->meta.fragment_path);
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        while ((t = set_steal_first(u->meta.names)))
                free(t);
        set_free(u->meta.names);

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        free(u->meta.instance);

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        free(u);
}

UnitActiveState unit_active_state(Unit *u) {
        assert(u);

        if (u->meta.load_state != UNIT_LOADED)
                return UNIT_INACTIVE;

        return UNIT_VTABLE(u)->active_state(u);
}

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const char* unit_sub_state_to_string(Unit *u) {
        assert(u);

        return UNIT_VTABLE(u)->sub_state_to_string(u);
}

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static void complete_move(Set **s, Set **other) {
        assert(s);
        assert(other);
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        if (!*other)
                return;
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        if (*s)
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                set_move(*s, *other);
        else {
                *s = *other;
                *other = NULL;
        }
}
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static void merge_names(Unit *u, Unit *other) {
        char *t;
        Iterator i;
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        assert(u);
        assert(other);

        complete_move(&u->meta.names, &other->meta.names);

        while ((t = set_steal_first(other->meta.names)))
                free(t);

        set_free(other->meta.names);
        other->meta.names = NULL;
        other->meta.id = NULL;

        SET_FOREACH(t, u->meta.names, i)
                assert_se(hashmap_replace(u->meta.manager->units, t, u) == 0);
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}

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static void merge_dependencies(Unit *u, Unit *other, UnitDependency d) {
        Iterator i;
        Unit *back;
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        int r;
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        assert(u);
        assert(other);
        assert(d < _UNIT_DEPENDENCY_MAX);

        SET_FOREACH(back, other->meta.dependencies[d], i) {
                UnitDependency k;

                for (k = 0; k < _UNIT_DEPENDENCY_MAX; k++)
                        if ((r = set_remove_and_put(back->meta.dependencies[k], other, u)) < 0) {

                                if (r == -EEXIST)
                                        set_remove(back->meta.dependencies[k], other);
                                else
                                        assert(r == -ENOENT);
                        }
        }

        complete_move(&u->meta.dependencies[d], &other->meta.dependencies[d]);

        set_free(other->meta.dependencies[d]);
        other->meta.dependencies[d] = NULL;
}

int unit_merge(Unit *u, Unit *other) {
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        UnitDependency d;

        assert(u);
        assert(other);
        assert(u->meta.manager == other->meta.manager);
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        assert(u->meta.type != _UNIT_TYPE_INVALID);
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        other = unit_follow_merge(other);

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        if (other == u)
                return 0;

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        if (u->meta.type != other->meta.type)
                return -EINVAL;

        if (!streq_ptr(u->meta.instance, other->meta.instance))
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                return -EINVAL;

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        if (other->meta.load_state != UNIT_STUB &&
            other->meta.load_state != UNIT_FAILED)
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                return -EEXIST;
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        if (other->meta.job)
                return -EEXIST;

        if (unit_active_state(other) != UNIT_INACTIVE)
                return -EEXIST;

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        /* Merge names */
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        merge_names(u, other);
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        /* Merge dependencies */
        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
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                merge_dependencies(u, other, d);
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        other->meta.load_state = UNIT_MERGED;
        other->meta.merged_into = u;

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        /* If there is still some data attached to the other node, we
         * don't need it anymore, and can free it. */
        if (other->meta.load_state != UNIT_STUB)
                if (UNIT_VTABLE(other)->done)
                        UNIT_VTABLE(other)->done(other);

        unit_add_to_dbus_queue(u);
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        unit_add_to_cleanup_queue(other);

        return 0;
}

int unit_merge_by_name(Unit *u, const char *name) {
        Unit *other;
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        int r;
        char *s = NULL;
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        assert(u);
        assert(name);

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        if (unit_name_is_template(name)) {
                if (!u->meta.instance)
                        return -EINVAL;

                if (!(s = unit_name_replace_instance(name, u->meta.instance)))
                        return -ENOMEM;

                name = s;
        }

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        if (!(other = manager_get_unit(u->meta.manager, name)))
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                r = unit_add_name(u, name);
        else
                r = unit_merge(u, other);
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        free(s);
        return r;
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}

Unit* unit_follow_merge(Unit *u) {
        assert(u);

        while (u->meta.load_state == UNIT_MERGED)
                assert_se(u = u->meta.merged_into);

        return u;
}

int unit_add_exec_dependencies(Unit *u, ExecContext *c) {
        int r;

        assert(u);
        assert(c);

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        if (c->std_output != EXEC_OUTPUT_KERNEL && c->std_output != EXEC_OUTPUT_SYSLOG)
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                return 0;

        /* If syslog or kernel logging is requested, make sure our own
         * logging daemon is run first. */

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        if ((r = unit_add_dependency_by_name(u, UNIT_AFTER, SPECIAL_LOGGER_SOCKET, NULL)) < 0)
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                return r;

        if (u->meta.manager->running_as != MANAGER_SESSION)
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                if ((r = unit_add_dependency_by_name(u, UNIT_REQUIRES, SPECIAL_LOGGER_SOCKET, NULL)) < 0)
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                        return r;

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        return 0;
}

const char *unit_description(Unit *u) {
        assert(u);

        if (u->meta.description)
                return u->meta.description;

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        return u->meta.id;
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}

void unit_dump(Unit *u, FILE *f, const char *prefix) {
        char *t;
        UnitDependency d;
        Iterator i;
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        char *p2;
        const char *prefix2;
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        CGroupBonding *b;
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        char timestamp1[FORMAT_TIMESTAMP_MAX], timestamp2[FORMAT_TIMESTAMP_MAX];
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        assert(u);
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        assert(u->meta.type >= 0);
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        if (!prefix)
                prefix = "";
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        p2 = strappend(prefix, "\t");
        prefix2 = p2 ? p2 : prefix;
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        fprintf(f,
                "%s→ Unit %s:\n"
                "%s\tDescription: %s\n"
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                "%s\tInstance: %s\n"
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                "%s\tUnit Load State: %s\n"
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                "%s\tUnit Active State: %s\n"
                "%s\tActive Enter Timestamp: %s\n"
                "%s\tActive Exit Timestamp: %s\n",
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                prefix, u->meta.id,
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                prefix, unit_description(u),
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                prefix, strna(u->meta.instance),
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                prefix, unit_load_state_to_string(u->meta.load_state),
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                prefix, unit_active_state_to_string(unit_active_state(u)),
                prefix, strna(format_timestamp(timestamp1, sizeof(timestamp1), u->meta.active_enter_timestamp)),
                prefix, strna(format_timestamp(timestamp2, sizeof(timestamp2), u->meta.active_exit_timestamp)));
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        SET_FOREACH(t, u->meta.names, i)
                fprintf(f, "%s\tName: %s\n", prefix, t);

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        if (u->meta.fragment_path)
                fprintf(f, "%s\tFragment Path: %s\n", prefix, u->meta.fragment_path);

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        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++) {
                Unit *other;

                SET_FOREACH(other, u->meta.dependencies[d], i)
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                        fprintf(f, "%s\t%s: %s\n", prefix, unit_dependency_to_string(d), other->meta.id);
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        }

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        if (u->meta.load_state == UNIT_LOADED) {
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                fprintf(f,
                        "%s\tRecursive Stop: %s\n"
                        "%s\tStop When Unneeded: %s\n",
                        prefix, yes_no(u->meta.recursive_stop),
                        prefix, yes_no(u->meta.stop_when_unneeded));

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                LIST_FOREACH(by_unit, b, u->meta.cgroup_bondings)
                        fprintf(f, "%s\tControlGroup: %s:%s\n",
                                prefix, b->controller, b->path);
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                if (UNIT_VTABLE(u)->dump)
                        UNIT_VTABLE(u)->dump(u, f, prefix2);
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        } else if (u->meta.load_state == UNIT_MERGED)
                fprintf(f,
                        "%s\tMerged into: %s\n",
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                        prefix, u->meta.merged_into->meta.id);
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        if (u->meta.job)
                job_dump(u->meta.job, f, prefix2);

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        free(p2);
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}

/* Common implementation for multiple backends */
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int unit_load_fragment_and_dropin(Unit *u) {
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        int r;

        assert(u);

        /* Load a .service file */
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        if ((r = unit_load_fragment(u)) < 0)
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                return r;

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        if (u->meta.load_state == UNIT_STUB)
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                return -ENOENT;

        /* Load drop-in directory data */
        if ((r = unit_load_dropin(unit_follow_merge(u))) < 0)
                return r;

        return 0;
}

/* Common implementation for multiple backends */
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int unit_load_fragment_and_dropin_optional(Unit *u) {
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        int r;
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        assert(u);

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        /* Same as unit_load_fragment_and_dropin(), but whether
         * something can be loaded or not doesn't matter. */

        /* Load a .service file */
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        if ((r = unit_load_fragment(u)) < 0)
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                return r;

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        if (u->meta.load_state == UNIT_STUB)
                u->meta.load_state = UNIT_LOADED;
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        /* Load drop-in directory data */
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        if ((r = unit_load_dropin(unit_follow_merge(u))) < 0)
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                return r;

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        return 0;
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}

int unit_load(Unit *u) {
        int r;

        assert(u);

        if (u->meta.in_load_queue) {
                LIST_REMOVE(Meta, load_queue, u->meta.manager->load_queue, &u->meta);
                u->meta.in_load_queue = false;
        }

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        if (u->meta.type == _UNIT_TYPE_INVALID)
                return -EINVAL;

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        if (u->meta.load_state != UNIT_STUB)
                return 0;

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        if (UNIT_VTABLE(u)->load)
                if ((r = UNIT_VTABLE(u)->load(u)) < 0)
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                        goto fail;
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        if (u->meta.load_state == UNIT_STUB) {
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                r = -ENOENT;
                goto fail;
        }

        assert((u->meta.load_state != UNIT_MERGED) == !u->meta.merged_into);

        unit_add_to_dbus_queue(unit_follow_merge(u));
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        return 0;

fail:
        u->meta.load_state = UNIT_FAILED;
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        unit_add_to_dbus_queue(u);
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        log_error("Failed to load configuration for %s: %s", u->meta.id, strerror(-r));
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        return r;
}

/* Errors:
 *         -EBADR:    This unit type does not support starting.
 *         -EALREADY: Unit is already started.
 *         -EAGAIN:   An operation is already in progress. Retry later.
 */
int unit_start(Unit *u) {
        UnitActiveState state;

        assert(u);

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        /* If this is already (being) started, then this will
         * succeed. Note that this will even succeed if this unit is
         * not startable by the user. This is relied on to detect when
         * we need to wait for units and when waiting is finished. */
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        state = unit_active_state(u);
        if (UNIT_IS_ACTIVE_OR_RELOADING(state))
                return -EALREADY;

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        /* If it is stopped, but we cannot start it, then fail */
        if (!UNIT_VTABLE(u)->start)
                return -EBADR;

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        /* 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
         * restart" state where it waits for a holdoff timer to elapse
         * before it will start again. */

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        unit_add_to_dbus_queue(u);
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        return UNIT_VTABLE(u)->start(u);
}

bool unit_can_start(Unit *u) {
        assert(u);

        return !!UNIT_VTABLE(u)->start;
}

/* Errors:
 *         -EBADR:    This unit type does not support stopping.
 *         -EALREADY: Unit is already stopped.
 *         -EAGAIN:   An operation is already in progress. Retry later.
 */
int unit_stop(Unit *u) {
        UnitActiveState state;

        assert(u);

        state = unit_active_state(u);
        if (state == UNIT_INACTIVE)
                return -EALREADY;

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        if (!UNIT_VTABLE(u)->stop)
                return -EBADR;

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        unit_add_to_dbus_queue(u);
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        return UNIT_VTABLE(u)->stop(u);
}

/* Errors:
 *         -EBADR:    This unit type does not support reloading.
 *         -ENOEXEC:  Unit is not started.
 *         -EAGAIN:   An operation is already in progress. Retry later.
 */
int unit_reload(Unit *u) {
        UnitActiveState state;

        assert(u);

        if (!unit_can_reload(u))
                return -EBADR;

        state = unit_active_state(u);
        if (unit_active_state(u) == UNIT_ACTIVE_RELOADING)
                return -EALREADY;

        if (unit_active_state(u) != UNIT_ACTIVE)
                return -ENOEXEC;

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        unit_add_to_dbus_queue(u);
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        return UNIT_VTABLE(u)->reload(u);
}

bool unit_can_reload(Unit *u) {
        assert(u);

        if (!UNIT_VTABLE(u)->reload)
                return false;

        if (!UNIT_VTABLE(u)->can_reload)
                return true;

        return UNIT_VTABLE(u)->can_reload(u);
}

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static void unit_check_uneeded(Unit *u) {
        Iterator i;
        Unit *other;

        assert(u);

        /* If this service shall be shut down when unneeded then do
         * so. */

        if (!u->meta.stop_when_unneeded)
                return;

        if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(u)))
                return;

        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRED_BY], i)
                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        return;

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        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRED_BY_OVERRIDABLE], i)
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                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        return;

        SET_FOREACH(other, u->meta.dependencies[UNIT_WANTED_BY], i)
                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        return;

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        log_debug("Service %s is not needed anymore. Stopping.", u->meta.id);
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        /* Ok, nobody needs us anymore. Sniff. Then let's commit suicide */
        manager_add_job(u->meta.manager, JOB_STOP, u, JOB_FAIL, true, NULL);
}

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static void retroactively_start_dependencies(Unit *u) {
        Iterator i;
        Unit *other;

        assert(u);
        assert(UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(u)));

        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES], i)
                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);

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        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES_OVERRIDABLE], i)
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                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);

        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUISITE], i)
                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);

        SET_FOREACH(other, u->meta.dependencies[UNIT_WANTS], i)
                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);

        SET_FOREACH(other, u->meta.dependencies[UNIT_CONFLICTS], i)
                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
                        manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
}

static void retroactively_stop_dependencies(Unit *u) {
        Iterator i;
        Unit *other;

        assert(u);
        assert(UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(u)));

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        if (u->meta.recursive_stop) {
                /* Pull down units need us recursively if enabled */
                SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRED_BY], i)
                        if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                                manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
        }

        /* Garbage collect services that might not be needed anymore, if enabled */
        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES], i)
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                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
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                        unit_check_uneeded(other);
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        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES_OVERRIDABLE], i)
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                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        unit_check_uneeded(other);
        SET_FOREACH(other, u->meta.dependencies[UNIT_WANTS], i)
                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        unit_check_uneeded(other);
        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUISITE], i)
                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        unit_check_uneeded(other);
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        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUISITE_OVERRIDABLE], i)
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                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
                        unit_check_uneeded(other);
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}

void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns) {
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        bool unexpected = false;

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        assert(u);
        assert(os < _UNIT_ACTIVE_STATE_MAX);
        assert(ns < _UNIT_ACTIVE_STATE_MAX);

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        /* Note that this is called for all low-level state changes,
         * even if they might map to the same high-level
         * UnitActiveState! That means that ns == os is OK an expected
         * behaviour here. For example: if a mount point is remounted
         * this function will be called too and the utmp code below
         * relies on that! */
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        if (!UNIT_IS_ACTIVE_OR_RELOADING(os) && UNIT_IS_ACTIVE_OR_RELOADING(ns))
                u->meta.active_enter_timestamp = now(CLOCK_REALTIME);
        else if (UNIT_IS_ACTIVE_OR_RELOADING(os) && !UNIT_IS_ACTIVE_OR_RELOADING(ns))
                u->meta.active_exit_timestamp = now(CLOCK_REALTIME);

        if (u->meta.job) {

                if (u->meta.job->state == JOB_WAITING)

                        /* So we reached a different state for this
                         * job. Let's see if we can run it now if it
                         * failed previously due to EAGAIN. */
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                        job_add_to_run_queue(u->meta.job);
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                else {
                        assert(u->meta.job->state == JOB_RUNNING);

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                        /* Let's check whether this state change
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                         * constitutes a finished job, or maybe
                         * cotradicts a running job and hence needs to
                         * invalidate jobs. */

                        switch (u->meta.job->type) {

                        case JOB_START:
                        case JOB_VERIFY_ACTIVE:

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                                if (UNIT_IS_ACTIVE_OR_RELOADING(ns))
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                                        job_finish_and_invalidate(u->meta.job, true);
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                                else if (ns != UNIT_ACTIVATING) {
                                        unexpected = true;
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                                        job_finish_and_invalidate(u->meta.job, false);
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                                }
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                                break;

                        case JOB_RELOAD:
                        case JOB_RELOAD_OR_START:

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                                if (ns == UNIT_ACTIVE)
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                                        job_finish_and_invalidate(u->meta.job, true);
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                                else if (ns != UNIT_ACTIVATING && ns != UNIT_ACTIVE_RELOADING) {
                                        unexpected = true;
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                                        job_finish_and_invalidate(u->meta.job, false);
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                                }
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                                break;

                        case JOB_STOP:
                        case JOB_RESTART:
                        case JOB_TRY_RESTART:

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                                if (ns == UNIT_INACTIVE)
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                                        job_finish_and_invalidate(u->meta.job, true);
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                                else if (ns != UNIT_DEACTIVATING) {
                                        unexpected = true;
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                                        job_finish_and_invalidate(u->meta.job, false);
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                                }
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                                break;

                        default:
                                assert_not_reached("Job type unknown");
                        }
                }
        }

        /* If this state change happened without being requested by a
         * job, then let's retroactively start or stop dependencies */

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        if (unexpected) {
                if (UNIT_IS_INACTIVE_OR_DEACTIVATING(os) && UNIT_IS_ACTIVE_OR_ACTIVATING(ns))
                        retroactively_start_dependencies(u);
                else if (UNIT_IS_ACTIVE_OR_ACTIVATING(os) && UNIT_IS_INACTIVE_OR_DEACTIVATING(ns))
                        retroactively_stop_dependencies(u);
        }
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        /* Some names are special */
        if (UNIT_IS_ACTIVE_OR_RELOADING(ns)) {
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                if (unit_has_name(u, SPECIAL_DBUS_SERVICE)) {
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                        /* The bus just might have become available,
                         * hence try to connect to it, if we aren't
                         * yet connected. */
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                        bus_init_system(u->meta.manager);
                        bus_init_api(u->meta.manager);
                }

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                if (unit_has_name(u, SPECIAL_SYSLOG_SERVICE))
                        /* The syslog daemon just might have become
                         * available, hence try to connect to it, if
                         * we aren't yet connected. */
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                        log_open_syslog();
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                if (u->meta.type == UNIT_MOUNT)
                        /* Another directory became available, let's
                         * check if that is enough to write our utmp
                         * entry. */
                        manager_write_utmp_reboot(u->meta.manager);

                if (u->meta.type == UNIT_TARGET)
                        /* A target got activated, maybe this is a runlevel? */
                        manager_write_utmp_runlevel(u->meta.manager, u);

        } else if (!UNIT_IS_ACTIVE_OR_RELOADING(ns)) {
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                if (unit_has_name(u, SPECIAL_SYSLOG_SERVICE))
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                        /* The syslog daemon might just have
                         * terminated, hence try to disconnect from
                         * it. */
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                        log_close_syslog();
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                /* We don't care about D-Bus here, since we'll get an
                 * asynchronous notification for it anyway. */
        }

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        /* Maybe we finished startup and are now ready for being
         * stopped because unneeded? */
        unit_check_uneeded(u);
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        unit_add_to_dbus_queue(u);
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}

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int unit_watch_fd(Unit *u, int fd, uint32_t events, Watch *w) {
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        struct epoll_event ev;

        assert(u);
        assert(fd >= 0);
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        assert(w);
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        assert(w->type == WATCH_INVALID || (w->type == WATCH_FD && w->fd == fd && w->data.unit == u));
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        zero(ev);
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        ev.data.ptr = w;
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        ev.events = events;

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        if (epoll_ctl(u->meta.manager->epoll_fd,
                      w->type == WATCH_INVALID ? EPOLL_CTL_ADD : EPOLL_CTL_MOD,
                      fd,
                      &ev) < 0)
                return -errno;
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        w->fd = fd;
        w->type = WATCH_FD;