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core: add new PropagateStopTo= dependency (and inverse)

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This takes inspiration from PropagatesReloadTo=, but propagates
stop jobs instead of restart jobs.

This is defined based on exactly two atoms: UNIT_ATOM_PROPAGATE_STOP +
UNIT_ATOM_RETROACTIVE_STOP_ON_STOP. The former ensures that when the
unit the dependency is originating from is stopped based on user
request, we'll propagate the stop job to the target unit, too. In
addition, when the originating unit suddenly stops from external causes
the stopping is propagated too. Note that this does *not* include the
UNIT_ATOM_CANNOT_BE_ACTIVE_WITHOUT atom (which is used by BoundBy=),
i.e. this dependency is purely about propagating "edges" and not
"levels", i.e. it's about propagating specific events, instead of
continious states.

This is supposed to be useful for dependencies between .mount units and
their backing .device units. So far we either placed a BindsTo= or
Requires= dependency between them. The former gave a very clear binding
of the to units together, however was problematic if users establish
mounnts manually with different block device sources than our
configuration defines, as we there might come to the conclusion that the
backing device was absent and thus we need to umount again what the user
mounted. By combining Requires= with the new StopPropagatedFrom= (i.e.
the inverse PropagateStopTo=) we can get behaviour that matches BindsTo=
in every single atom but one: UNIT_ATOM_CANNOT_BE_ACTIVE_WITHOUT is
absent, and hence the level-triggered logic doesn't apply.

Replaces: #11340
This commit is contained in:
Lennart Poettering 2021-04-13 22:30:31 +02:00
parent 629b2a6f7b
commit ffec78c05b
9 changed files with 46 additions and 8 deletions
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12
man/org.freedesktop.systemd1.xml
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@ -1640,6 +1640,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly as ReloadPropagatedFrom = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly as PropagatesStopTo = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly as StopPropagatedFrom = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly as JoinsNamespaceOf = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly as SliceOf = ['...', ...];
@ -1779,6 +1783,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
<!--property ReloadPropagatedFrom is not documented!-->
<!--property PropagatesStopTo is not documented!-->
<!--property StopPropagatedFrom is not documented!-->
<!--property JoinsNamespaceOf is not documented!-->
<!--property SliceOf is not documented!-->
@ -1919,6 +1927,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
<variablelist class="dbus-property" generated="True" extra-ref="ReloadPropagatedFrom"/>
<variablelist class="dbus-property" generated="True" extra-ref="PropagatesStopTo"/>
<variablelist class="dbus-property" generated="True" extra-ref="StopPropagatedFrom"/>
<variablelist class="dbus-property" generated="True" extra-ref="JoinsNamespaceOf"/>
<variablelist class="dbus-property" generated="True" extra-ref="SliceOf"/>

21
man/systemd.unit.xml
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@ -787,13 +787,20 @@
<term><varname>PropagatesReloadTo=</varname></term>
<term><varname>ReloadPropagatedFrom=</varname></term>
<listitem><para>A space-separated list of one or more units
where reload requests on this unit will be propagated to, or
reload requests on the other unit will be propagated to this
unit, respectively. Issuing a reload request on a unit will
automatically also enqueue a reload request on all units that
the reload request shall be propagated to via these two
settings.</para></listitem>
<listitem><para>A space-separated list of one or more units to which reload requests from this unit
shall be propagated to, or units from which reload requests shall be propagated to this unit,
respectively. Issuing a reload request on a unit will automatically also enqueue reload requests on
all units that are linked to it using these two settings.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PropagatesStopTo=</varname></term>
<term><varname>StopPropagatedFrom=</varname></term>
<listitem><para>A space-separated list of one or more units to which stop requests from this unit
shall be propagated to, or units from which stop requests shall be propagated to this unit,
respectively. Issuing a stop request on a unit will automatically also enqueue stop requests on all
units that are linked to it using these two settings.</para></listitem>
</varlistentry>
<varlistentry>

2
src/basic/unit-def.c
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@ -280,6 +280,8 @@ static const char* const unit_dependency_table[_UNIT_DEPENDENCY_MAX] = {
[UNIT_TRIGGERED_BY] = "TriggeredBy",
[UNIT_PROPAGATES_RELOAD_TO] = "PropagatesReloadTo",
[UNIT_RELOAD_PROPAGATED_FROM] = "ReloadPropagatedFrom",
[UNIT_PROPAGATES_STOP_TO] = "PropagatesStopTo",
[UNIT_STOP_PROPAGATED_FROM] = "StopPropagatedFrom",
[UNIT_JOINS_NAMESPACE_OF] = "JoinsNamespaceOf",
[UNIT_REFERENCES] = "References",
[UNIT_REFERENCED_BY] = "ReferencedBy",

4
src/basic/unit-def.h
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@ -239,6 +239,10 @@ typedef enum UnitDependency {
UNIT_PROPAGATES_RELOAD_TO,
UNIT_RELOAD_PROPAGATED_FROM,
/* Propagate stops */
UNIT_PROPAGATES_STOP_TO,
UNIT_STOP_PROPAGATED_FROM,
/* Joins namespace of */
UNIT_JOINS_NAMESPACE_OF,

4
src/core/dbus-unit.c
View File

@ -870,6 +870,8 @@ const sd_bus_vtable bus_unit_vtable[] = {
SD_BUS_PROPERTY("TriggeredBy", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("PropagatesReloadTo", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("ReloadPropagatedFrom", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("PropagatesStopTo", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("StopPropagatedFrom", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("JoinsNamespaceOf", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("SliceOf", "as", property_get_dependencies, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("RequiresMountsFor", "as", property_get_requires_mounts_for, offsetof(Unit, requires_mounts_for), SD_BUS_VTABLE_PROPERTY_CONST),
@ -2302,6 +2304,8 @@ static int bus_unit_set_transient_property(
UNIT_ON_FAILURE,
UNIT_PROPAGATES_RELOAD_TO,
UNIT_RELOAD_PROPAGATED_FROM,
UNIT_PROPAGATES_STOP_TO,
UNIT_STOP_PROPAGATED_FROM,
UNIT_JOINS_NAMESPACE_OF))
return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Dependency type %s may not be created transiently.", unit_dependency_to_string(d));

2
src/core/load-fragment-gperf.gperf.in
View File

@ -269,6 +269,8 @@ Unit.PropagatesReloadTo, config_parse_unit_deps,
Unit.PropagateReloadTo, config_parse_unit_deps, UNIT_PROPAGATES_RELOAD_TO, 0
Unit.ReloadPropagatedFrom, config_parse_unit_deps, UNIT_RELOAD_PROPAGATED_FROM, 0
Unit.PropagateReloadFrom, config_parse_unit_deps, UNIT_RELOAD_PROPAGATED_FROM, 0
Unit.PropagatesStopTo, config_parse_unit_deps, UNIT_PROPAGATES_STOP_TO, 0
Unit.StopPropagatedFrom, config_parse_unit_deps, UNIT_STOP_PROPAGATED_FROM, 0
Unit.PartOf, config_parse_unit_deps, UNIT_PART_OF, 0
Unit.JoinsNamespaceOf, config_parse_unit_deps, UNIT_JOINS_NAMESPACE_OF, 0
Unit.RequiresOverridable, config_parse_obsolete_unit_deps, UNIT_REQUIRES, 0

5
src/core/unit-dependency-atom.c
View File

@ -68,6 +68,9 @@ static const UnitDependencyAtom atom_map[_UNIT_DEPENDENCY_MAX] = {
UNIT_ATOM_RETROACTIVE_STOP_ON_START |
UNIT_ATOM_PROPAGATE_STOP_FAILURE,
[UNIT_PROPAGATES_STOP_TO] = UNIT_ATOM_RETROACTIVE_STOP_ON_STOP |
UNIT_ATOM_PROPAGATE_STOP,
/* These are simple dependency types: they consist of a single atom only */
[UNIT_BEFORE] = UNIT_ATOM_BEFORE,
[UNIT_AFTER] = UNIT_ATOM_AFTER,
@ -86,6 +89,7 @@ static const UnitDependencyAtom atom_map[_UNIT_DEPENDENCY_MAX] = {
* have no effect of their own, they all map to no atoms at all, i.e. the value 0. */
[UNIT_RELOAD_PROPAGATED_FROM] = 0,
[UNIT_ON_FAILURE_OF] = 0,
[UNIT_STOP_PROPAGATED_FROM] = 0,
};
UnitDependencyAtom unit_dependency_to_atom(UnitDependency d) {
@ -149,7 +153,6 @@ UnitDependency unit_dependency_from_unique_atom(UnitDependencyAtom atom) {
UNIT_ATOM_PROPAGATE_START_FAILURE |
UNIT_ATOM_PINS_STOP_WHEN_UNNEEDED |
UNIT_ATOM_DEFAULT_TARGET_DEPENDENCIES:
case UNIT_ATOM_RETROACTIVE_STOP_ON_STOP:
return UNIT_BOUND_BY;
case UNIT_ATOM_PULL_IN_STOP |

2
src/core/unit.c
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@ -2879,6 +2879,8 @@ int unit_add_dependency(
[UNIT_TRIGGERED_BY] = UNIT_TRIGGERS,
[UNIT_PROPAGATES_RELOAD_TO] = UNIT_RELOAD_PROPAGATED_FROM,
[UNIT_RELOAD_PROPAGATED_FROM] = UNIT_PROPAGATES_RELOAD_TO,
[UNIT_PROPAGATES_STOP_TO] = UNIT_STOP_PROPAGATED_FROM,
[UNIT_STOP_PROPAGATED_FROM] = UNIT_PROPAGATES_STOP_TO,
[UNIT_JOINS_NAMESPACE_OF] = UNIT_JOINS_NAMESPACE_OF, /* symmetric! 👓 */
[UNIT_IN_SLICE] = UNIT_SLICE_OF,
[UNIT_SLICE_OF] = UNIT_IN_SLICE,

2
test/fuzz/fuzz-unit-file/directives.service
View File

@ -80,6 +80,7 @@ PartOf=
PropagateReloadFrom=
PropagateReloadTo=
PropagatesReloadTo=
PropagatesStopTo=
RebootArgument=
RefuseManualStart=
RefuseManualStop=
@ -97,6 +98,7 @@ StartLimitBurst=
StartLimitInterval=
StartLimitIntervalSec=
StopWhenUnneeded=
StopPropagatedFrom=
SuccessAction=
SuccessActionExitStatus=
Wants=