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core: introduce new KillMode=mixed which sends SIGTERM only to the main process, but SIGKILL to all daemon processes

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This should fix some race with terminating systemd --user, where the
system systemd instance might race against the user systemd instance
when sending SIGTERM.
This commit is contained in:
Lennart Poettering 2014-01-29 13:38:55 +01:00
parent 373f14222e
commit 58ea275a68
5 changed files with 56 additions and 27 deletions
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77
man/systemd.kill.xml
View File

@ -44,39 +44,44 @@
<refnamediv>
<refname>systemd.kill</refname>
<refpurpose>Kill environment configuration</refpurpose>
<refpurpose>Process killing procedure
configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>service</replaceable>.service</filename>,
<filename><replaceable>socket</replaceable>.socket</filename>,
<filename><replaceable>mount</replaceable>.mount</filename>,
<filename><replaceable>swap</replaceable>.swap</filename></para>
<filename><replaceable>swap</replaceable>.swap</filename>,
<filename><replaceable>scope</replaceable>.scope</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>Unit configuration files for services, sockets,
mount points and swap devices share a subset of
configuration options which define the process killing
parameters of spawned processes.</para>
mount points, swap devices and scopes share a subset
of configuration options which define the
killing procedure of processes belonging to the unit.</para>
<para>This man page lists the configuration options
shared by these four unit types. See
shared by these five unit types. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration
files, and
for the common options shared by all unit
configuration files, and
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information on the specific unit
configuration files. The execution specific
and
<citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information on the configuration file options
specific to each unit type.</para>
<para>The kill procedure
configuration options are configured in the [Service],
[Socket], [Mount], or [Swap] section, depending on the unit
type.</para>
[Socket], [Mount] or [Swap] section, depending on the
unit type.</para>
</refsect1>
<refsect1>
@ -87,32 +92,40 @@
<varlistentry>
<term><varname>KillMode=</varname></term>
<listitem><para>Specifies how
processes of this service shall be
processes of this unit shall be
killed. One of
<option>control-group</option>,
<option>process</option>,
<option>mixed</option>,
<option>none</option>.</para>
<para>If set to
<option>control-group</option>, all
remaining processes in the control
group of this unit will be terminated
on unit stop (for services: after the
group of this unit will be killed on
unit stop (for services: after the
stop command is executed, as
configured with
<varname>ExecStop=</varname>). If set
to <option>process</option>, only the
main process itself is killed. If set
to <option>none</option>, no process is
to <option>mixed</option> the
<constant>SIGTERM</constant> signal
(see below) is sent to the main
process while the subsequent
<constant>SIGKILL</constant> signal
(see below) is sent to all remaining
processes of the unit's control
group. If set to
<option>none</option>, no process is
killed. In this case only the stop
command will be executed on unit
stop, but no process be killed
command will be executed on unit stop,
but no process be killed
otherwise. Processes remaining alive
after stop are left in their control
group and the control group continues
to exist after stop unless it is
empty. Defaults to
<option>control-group</option>.</para>
empty.</para>
<para>Processes will first be
terminated via
@ -133,14 +146,24 @@
option). See
<citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for more
information.</para></listitem>
information.</para>
<para>Defaults to
<option>control-group</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>KillSignal=</varname></term>
<listitem><para>Specifies which signal
to use when killing a
service. Defaults to <constant>SIGTERM</constant>.
to use when killing a service. This
controls the signal that is sent as
first step of shutting down a unit
(see above), and is usually followed
by <constant>SIGKILL</constant> (see
above and below). For a list of valid
signals, see
<citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Defaults
to <constant>SIGTERM</constant>.
</para></listitem>
</varlistentry>
@ -184,7 +207,9 @@
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
<citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>

1
src/core/kill.c
View File

@ -52,6 +52,7 @@ void kill_context_dump(KillContext *c, FILE *f, const char *prefix) {
static const char* const kill_mode_table[_KILL_MODE_MAX] = {
[KILL_CONTROL_GROUP] = "control-group",
[KILL_PROCESS] = "process",
[KILL_MIXED] = "mixed",
[KILL_NONE] = "none"
};

1
src/core/kill.h
View File

@ -32,6 +32,7 @@ typedef enum KillMode {
/* The kill mode is a property of a unit. */
KILL_CONTROL_GROUP = 0,
KILL_PROCESS,
KILL_MIXED,
KILL_NONE,
_KILL_MODE_MAX,
_KILL_MODE_INVALID = -1

3
src/core/unit.c
View File

@ -2966,7 +2966,7 @@ int unit_kill_context(
}
}
if (c->kill_mode == KILL_CONTROL_GROUP && u->cgroup_path) {
if ((c->kill_mode == KILL_CONTROL_GROUP || (c->kill_mode == KILL_MIXED && sigkill)) && u->cgroup_path) {
_cleanup_set_free_ Set *pid_set = NULL;
/* Exclude the main/control pids from being killed via the cgroup */
@ -2980,6 +2980,7 @@ int unit_kill_context(
log_warning_unit(u->id, "Failed to kill control group: %s", strerror(-r));
} else if (r > 0) {
wait_for_exit = true;
if (c->send_sighup) {
set_free(pid_set);

1
units/user@.service.in
View File

@ -15,3 +15,4 @@ PAMName=systemd-user
Type=notify
ExecStart=-@rootlibexecdir@/systemd --user
Slice=user-%i.slice
KillMode=mixed