Systemd/src/core/unit.h
Michal Schmidt e0209d83e7 core: add NOP jobs, job type collapsing
Two of our current job types are special:
JOB_TRY_RESTART, JOB_RELOAD_OR_START.

They differ from other job types by being sensitive to the unit active state.
They perform some action when the unit is active and some other action
otherwise. This raises a question: when exactly should the unit state be
checked to make the decision?

Currently the unit state is checked when the job becomes runnable. It's more
sensible to check the state immediately when the job is added by the user.
When the user types "systemctl try-restart foo.service", he really intends
to restart the service if it's running right now. If it isn't running right
now, the restart is pointless.

Consider the example (from Bugzilla[1]):

sleep.service takes some time to start.
hello.service has After=sleep.service.
Both services get started. Two jobs will appear:
 hello.service/start  waiting
 sleep.service/start  running
Then someone runs "systemctl try-restart hello.service".

Currently the try-restart operation will block and wait for
sleep.service/start to complete.

The correct result is to complete the try-restart operation immediately
with success, because hello.service is not running. The two original
jobs must not be disturbed by this.

To fix this we introduce two new concepts:
- a new job type: JOB_NOP
  A JOB_NOP job does not do anything to the unit. It does not pull in any
  dependencies. It is always immediately runnable. When installed to a unit,
  it sits in a special slot (u->nop_job) where it never conflicts with
  the installed job (u->job) of a different type. It never merges with jobs
  of other types, but it can merge into an already installed JOB_NOP job.

- "collapsing" of job types
  When a job of one of the two special types is added, the state of the unit
  is checked immediately and the job type changes:
  JOB_TRY_RESTART     -> JOB_RESTART or JOB_NOP
  JOB_RELOAD_OR_START -> JOB_RELOAD or JOB_START
  Should a job type JOB_RELOAD_OR_START appear later during job merging, it
  collapses immediately afterwards.
  Collapsing actually makes some things simpler, because there are now fewer
  job types that are allowed in the transaction.

[1] Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=753586
2012-04-25 18:38:27 +02:00

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C

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
#ifndef foounithfoo
#define foounithfoo
/***
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 Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <stdbool.h>
#include <stdlib.h>
typedef struct Unit Unit;
typedef struct UnitVTable UnitVTable;
typedef enum UnitType UnitType;
typedef enum UnitLoadState UnitLoadState;
typedef enum UnitActiveState UnitActiveState;
typedef enum UnitDependency UnitDependency;
typedef struct UnitRef UnitRef;
#include "set.h"
#include "util.h"
#include "list.h"
#include "socket-util.h"
#include "execute.h"
#include "condition.h"
#include "install.h"
enum UnitType {
UNIT_SERVICE = 0,
UNIT_SOCKET,
UNIT_TARGET,
UNIT_DEVICE,
UNIT_MOUNT,
UNIT_AUTOMOUNT,
UNIT_SNAPSHOT,
UNIT_TIMER,
UNIT_SWAP,
UNIT_PATH,
_UNIT_TYPE_MAX,
_UNIT_TYPE_INVALID = -1
};
enum UnitLoadState {
UNIT_STUB,
UNIT_LOADED,
UNIT_ERROR,
UNIT_MERGED,
UNIT_MASKED,
_UNIT_LOAD_STATE_MAX,
_UNIT_LOAD_STATE_INVALID = -1
};
enum UnitActiveState {
UNIT_ACTIVE,
UNIT_RELOADING,
UNIT_INACTIVE,
UNIT_FAILED,
UNIT_ACTIVATING,
UNIT_DEACTIVATING,
_UNIT_ACTIVE_STATE_MAX,
_UNIT_ACTIVE_STATE_INVALID = -1
};
static inline bool UNIT_IS_ACTIVE_OR_RELOADING(UnitActiveState t) {
return t == UNIT_ACTIVE || t == UNIT_RELOADING;
}
static inline bool UNIT_IS_ACTIVE_OR_ACTIVATING(UnitActiveState t) {
return t == UNIT_ACTIVE || t == UNIT_ACTIVATING || t == UNIT_RELOADING;
}
static inline bool UNIT_IS_INACTIVE_OR_DEACTIVATING(UnitActiveState t) {
return t == UNIT_INACTIVE || t == UNIT_FAILED || t == UNIT_DEACTIVATING;
}
static inline bool UNIT_IS_INACTIVE_OR_FAILED(UnitActiveState t) {
return t == UNIT_INACTIVE || t == UNIT_FAILED;
}
enum UnitDependency {
/* Positive dependencies */
UNIT_REQUIRES,
UNIT_REQUIRES_OVERRIDABLE,
UNIT_REQUISITE,
UNIT_REQUISITE_OVERRIDABLE,
UNIT_WANTS,
UNIT_BIND_TO,
/* Inverse of the above */
UNIT_REQUIRED_BY, /* inverse of 'requires' and 'requisite' is 'required_by' */
UNIT_REQUIRED_BY_OVERRIDABLE, /* inverse of 'requires_overridable' and 'requisite_overridable' is 'soft_required_by' */
UNIT_WANTED_BY, /* inverse of 'wants' */
UNIT_BOUND_BY, /* inverse of 'bind_to' */
/* Negative dependencies */
UNIT_CONFLICTS, /* inverse of 'conflicts' is 'conflicted_by' */
UNIT_CONFLICTED_BY,
/* Order */
UNIT_BEFORE, /* inverse of 'before' is 'after' and vice versa */
UNIT_AFTER,
/* On Failure */
UNIT_ON_FAILURE,
/* Triggers (i.e. a socket triggers a service) */
UNIT_TRIGGERS,
UNIT_TRIGGERED_BY,
/* Propagate reloads */
UNIT_PROPAGATE_RELOAD_TO,
UNIT_PROPAGATE_RELOAD_FROM,
/* Reference information for GC logic */
UNIT_REFERENCES, /* Inverse of 'references' is 'referenced_by' */
UNIT_REFERENCED_BY,
_UNIT_DEPENDENCY_MAX,
_UNIT_DEPENDENCY_INVALID = -1
};
#include "manager.h"
#include "job.h"
#include "cgroup.h"
#include "cgroup-attr.h"
struct Unit {
Manager *manager;
UnitType type;
UnitLoadState load_state;
Unit *merged_into;
char *id; /* One name is special because we use it for identification. Points to an entry in the names set */
char *instance;
Set *names;
Set *dependencies[_UNIT_DEPENDENCY_MAX];
char *description;
char *fragment_path; /* if loaded from a config file this is the primary path to it */
usec_t fragment_mtime;
/* If there is something to do with this unit, then this is the installed job for it */
Job *job;
/* JOB_NOP jobs are special and can be installed without disturbing the real job. */
Job *nop_job;
usec_t job_timeout;
/* References to this */
LIST_HEAD(UnitRef, refs);
/* Conditions to check */
LIST_HEAD(Condition, conditions);
dual_timestamp condition_timestamp;
dual_timestamp inactive_exit_timestamp;
dual_timestamp active_enter_timestamp;
dual_timestamp active_exit_timestamp;
dual_timestamp inactive_enter_timestamp;
/* Counterparts in the cgroup filesystem */
CGroupBonding *cgroup_bondings;
CGroupAttribute *cgroup_attributes;
/* Per type list */
LIST_FIELDS(Unit, units_by_type);
/* Load queue */
LIST_FIELDS(Unit, load_queue);
/* D-Bus queue */
LIST_FIELDS(Unit, dbus_queue);
/* Cleanup queue */
LIST_FIELDS(Unit, cleanup_queue);
/* GC queue */
LIST_FIELDS(Unit, gc_queue);
/* Used during GC sweeps */
unsigned gc_marker;
/* When deserializing, temporarily store the job type for this
* unit here, if there was a job scheduled.
* Only for deserializing from a legacy version. New style uses full
* serialized jobs. */
int deserialized_job; /* This is actually of type JobType */
/* Error code when we didn't manage to load the unit (negative) */
int load_error;
/* Cached unit file state */
UnitFileState unit_file_state;
/* Garbage collect us we nobody wants or requires us anymore */
bool stop_when_unneeded;
/* Create default dependencies */
bool default_dependencies;
/* Refuse manual starting, allow starting only indirectly via dependency. */
bool refuse_manual_start;
/* Don't allow the user to stop this unit manually, allow stopping only indirectly via dependency. */
bool refuse_manual_stop;
/* Allow isolation requests */
bool allow_isolate;
/* Isolate OnFailure unit */
bool on_failure_isolate;
/* Ignore this unit when isolating */
bool ignore_on_isolate;
/* Ignore this unit when snapshotting */
bool ignore_on_snapshot;
/* Did the last condition check suceed? */
bool condition_result;
bool in_load_queue:1;
bool in_dbus_queue:1;
bool in_cleanup_queue:1;
bool in_gc_queue:1;
bool sent_dbus_new_signal:1;
bool no_gc:1;
bool in_audit:1;
};
struct UnitRef {
/* Keeps tracks of references to a unit. This is useful so
* that we can merge two units if necessary and correct all
* references to them */
Unit* unit;
LIST_FIELDS(UnitRef, refs);
};
#include "service.h"
#include "timer.h"
#include "socket.h"
#include "target.h"
#include "device.h"
#include "mount.h"
#include "automount.h"
#include "snapshot.h"
#include "swap.h"
#include "path.h"
struct UnitVTable {
const char *suffix;
/* How much memory does an object of this unit type need */
size_t object_size;
/* Config file sections this unit type understands, separated
* by NUL chars */
const char *sections;
/* This should reset all type-specific variables. This should
* not allocate memory, and is called with zero-initialized
* data. It should hence only initialize variables that need
* to be set != 0. */
void (*init)(Unit *u);
/* This should free all type-specific variables. It should be
* idempotent. */
void (*done)(Unit *u);
/* Actually load data from disk. This may fail, and should set
* load_state to UNIT_LOADED, UNIT_MERGED or leave it at
* UNIT_STUB if no configuration could be found. */
int (*load)(Unit *u);
/* If a a lot of units got created via enumerate(), this is
* where to actually set the state and call unit_notify(). */
int (*coldplug)(Unit *u);
void (*dump)(Unit *u, FILE *f, const char *prefix);
int (*start)(Unit *u);
int (*stop)(Unit *u);
int (*reload)(Unit *u);
int (*kill)(Unit *u, KillWho w, KillMode m, int signo, DBusError *error);
bool (*can_reload)(Unit *u);
/* Write all data that cannot be restored from other sources
* away using unit_serialize_item() */
int (*serialize)(Unit *u, FILE *f, FDSet *fds);
/* Restore one item from the serialization */
int (*deserialize_item)(Unit *u, const char *key, const char *data, FDSet *fds);
/* Boils down the more complex internal state of this unit to
* a simpler one that the engine can understand */
UnitActiveState (*active_state)(Unit *u);
/* Returns the substate specific to this unit type as
* string. This is purely information so that we can give the
* user a more fine grained explanation in which actual state a
* unit is in. */
const char* (*sub_state_to_string)(Unit *u);
/* Return true when there is reason to keep this entry around
* even nothing references it and it isn't active in any
* way */
bool (*check_gc)(Unit *u);
/* Return true when this unit is suitable for snapshotting */
bool (*check_snapshot)(Unit *u);
void (*fd_event)(Unit *u, int fd, uint32_t events, Watch *w);
void (*sigchld_event)(Unit *u, pid_t pid, int code, int status);
void (*timer_event)(Unit *u, uint64_t n_elapsed, Watch *w);
/* Check whether unit needs a daemon reload */
bool (*need_daemon_reload)(Unit *u);
/* Reset failed state if we are in failed state */
void (*reset_failed)(Unit *u);
/* Called whenever any of the cgroups this unit watches for
* ran empty */
void (*cgroup_notify_empty)(Unit *u);
/* Called whenever a process of this unit sends us a message */
void (*notify_message)(Unit *u, pid_t pid, char **tags);
/* Called whenever a name thus Unit registered for comes or
* goes away. */
void (*bus_name_owner_change)(Unit *u, const char *name, const char *old_owner, const char *new_owner);
/* Called whenever a bus PID lookup finishes */
void (*bus_query_pid_done)(Unit *u, const char *name, pid_t pid);
/* Called for each message received on the bus */
DBusHandlerResult (*bus_message_handler)(Unit *u, DBusConnection *c, DBusMessage *message);
/* Return the unit this unit is following */
Unit *(*following)(Unit *u);
/* Return the set of units that are following each other */
int (*following_set)(Unit *u, Set **s);
/* This is called for each unit type and should be used to
* enumerate existing devices and load them. However,
* everything that is loaded here should still stay in
* inactive state. It is the job of the coldplug() call above
* to put the units into the initial state. */
int (*enumerate)(Manager *m);
/* Type specific cleanups. */
void (*shutdown)(Manager *m);
/* When sending out PropertiesChanged signal, which properties
* shall be invalidated? This is a NUL separated list of
* strings, to minimize relocations a little. */
const char *bus_invalidating_properties;
/* The interface name */
const char *bus_interface;
/* Can units of this type have multiple names? */
bool no_alias:1;
/* Instances make no sense for this type */
bool no_instances:1;
/* Exclude from automatic gc */
bool no_gc:1;
/* Show status updates on the console */
bool show_status:1;
};
extern const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX];
#define UNIT_VTABLE(u) unit_vtable[(u)->type]
/* For casting a unit into the various unit types */
#define DEFINE_CAST(UPPERCASE, MixedCase) \
static inline MixedCase* UPPERCASE(Unit *u) { \
if (_unlikely_(!u || u->type != UNIT_##UPPERCASE)) \
return NULL; \
\
return (MixedCase*) u; \
}
/* For casting the various unit types into a unit */
#define UNIT(u) (&(u)->meta)
DEFINE_CAST(SOCKET, Socket);
DEFINE_CAST(TIMER, Timer);
DEFINE_CAST(SERVICE, Service);
DEFINE_CAST(TARGET, Target);
DEFINE_CAST(DEVICE, Device);
DEFINE_CAST(MOUNT, Mount);
DEFINE_CAST(AUTOMOUNT, Automount);
DEFINE_CAST(SNAPSHOT, Snapshot);
DEFINE_CAST(SWAP, Swap);
DEFINE_CAST(PATH, Path);
Unit *unit_new(Manager *m, size_t size);
void unit_free(Unit *u);
int unit_add_name(Unit *u, const char *name);
int unit_add_dependency(Unit *u, UnitDependency d, Unit *other, bool add_reference);
int unit_add_two_dependencies(Unit *u, UnitDependency d, UnitDependency e, Unit *other, bool add_reference);
int unit_add_dependency_by_name(Unit *u, UnitDependency d, const char *name, const char *filename, bool add_reference);
int unit_add_two_dependencies_by_name(Unit *u, UnitDependency d, UnitDependency e, const char *name, const char *path, bool add_reference);
int unit_add_dependency_by_name_inverse(Unit *u, UnitDependency d, const char *name, const char *filename, bool add_reference);
int unit_add_two_dependencies_by_name_inverse(Unit *u, UnitDependency d, UnitDependency e, const char *name, const char *path, bool add_reference);
int unit_add_exec_dependencies(Unit *u, ExecContext *c);
int unit_add_cgroup(Unit *u, CGroupBonding *b);
int unit_add_cgroup_from_text(Unit *u, const char *name);
int unit_add_default_cgroups(Unit *u);
CGroupBonding* unit_get_default_cgroup(Unit *u);
int unit_add_cgroup_attribute(Unit *u, const char *controller, const char *name, const char *value, CGroupAttributeMapCallback map_callback);
int unit_choose_id(Unit *u, const char *name);
int unit_set_description(Unit *u, const char *description);
bool unit_check_gc(Unit *u);
void unit_add_to_load_queue(Unit *u);
void unit_add_to_dbus_queue(Unit *u);
void unit_add_to_cleanup_queue(Unit *u);
void unit_add_to_gc_queue(Unit *u);
int unit_merge(Unit *u, Unit *other);
int unit_merge_by_name(Unit *u, const char *other);
Unit *unit_follow_merge(Unit *u);
int unit_load_fragment_and_dropin(Unit *u);
int unit_load_fragment_and_dropin_optional(Unit *u);
int unit_load(Unit *unit);
const char *unit_description(Unit *u);
bool unit_has_name(Unit *u, const char *name);
UnitActiveState unit_active_state(Unit *u);
const char* unit_sub_state_to_string(Unit *u);
void unit_dump(Unit *u, FILE *f, const char *prefix);
bool unit_can_reload(Unit *u);
bool unit_can_start(Unit *u);
bool unit_can_isolate(Unit *u);
int unit_start(Unit *u);
int unit_stop(Unit *u);
int unit_reload(Unit *u);
int unit_kill(Unit *u, KillWho w, KillMode m, int signo, DBusError *error);
void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns, bool reload_success);
int unit_watch_fd(Unit *u, int fd, uint32_t events, Watch *w);
void unit_unwatch_fd(Unit *u, Watch *w);
int unit_watch_pid(Unit *u, pid_t pid);
void unit_unwatch_pid(Unit *u, pid_t pid);
int unit_watch_timer(Unit *u, usec_t delay, Watch *w);
void unit_unwatch_timer(Unit *u, Watch *w);
int unit_watch_bus_name(Unit *u, const char *name);
void unit_unwatch_bus_name(Unit *u, const char *name);
bool unit_job_is_applicable(Unit *u, JobType j);
int set_unit_path(const char *p);
char *unit_dbus_path(Unit *u);
int unit_load_related_unit(Unit *u, const char *type, Unit **_found);
int unit_get_related_unit(Unit *u, const char *type, Unit **_found);
char *unit_name_printf(Unit *u, const char* text);
char *unit_full_printf(Unit *u, const char *text);
char **unit_full_printf_strv(Unit *u, char **l);
bool unit_can_serialize(Unit *u);
int unit_serialize(Unit *u, FILE *f, FDSet *fds);
void unit_serialize_item_format(Unit *u, FILE *f, const char *key, const char *value, ...) _printf_attr_(4,5);
void unit_serialize_item(Unit *u, FILE *f, const char *key, const char *value);
int unit_deserialize(Unit *u, FILE *f, FDSet *fds);
int unit_add_node_link(Unit *u, const char *what, bool wants);
int unit_coldplug(Unit *u);
void unit_status_printf(Unit *u, const char *status, const char *format, ...);
bool unit_need_daemon_reload(Unit *u);
void unit_reset_failed(Unit *u);
Unit *unit_following(Unit *u);
bool unit_pending_inactive(Unit *u);
bool unit_pending_active(Unit *u);
int unit_add_default_target_dependency(Unit *u, Unit *target);
int unit_following_set(Unit *u, Set **s);
UnitType unit_name_to_type(const char *n);
bool unit_name_is_valid(const char *n, bool template_ok);
void unit_trigger_on_failure(Unit *u);
bool unit_condition_test(Unit *u);
UnitFileState unit_get_unit_file_state(Unit *u);
Unit* unit_ref_set(UnitRef *ref, Unit *u);
void unit_ref_unset(UnitRef *ref);
#define UNIT_DEREF(ref) ((ref).unit)
const char *unit_load_state_to_string(UnitLoadState i);
UnitLoadState unit_load_state_from_string(const char *s);
const char *unit_active_state_to_string(UnitActiveState i);
UnitActiveState unit_active_state_from_string(const char *s);
const char *unit_dependency_to_string(UnitDependency i);
UnitDependency unit_dependency_from_string(const char *s);
#endif