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systemd/src/core/dbus.h
Lennart Poettering d8fdc62037 core: use an AF_UNIX/SOCK_DGRAM socket for cgroup agent notification
dbus-daemon currently uses a backlog of 30 on its D-bus system bus socket. On
overloaded systems this means that only 30 connections may be queued without
dbus-daemon processing them before further connection attempts fail. Our
cgroups-agent binary so far used D-Bus for its messaging, and hitting this
limit hence may result in us losing cgroup empty messages.

This patch adds a seperate cgroup agent socket of type AF_UNIX/SOCK_DGRAM.
Since sockets of these types need no connection set up, no listen() backlog
applies. Our cgroup-agent binary will hence simply block as long as it can't
enqueue its datagram message, so that we won't lose cgroup empty messages as
likely anymore.

This also rearranges the ordering of the processing of SIGCHLD signals, service
notification messages (sd_notify()...) and the two types of cgroup
notifications (inotify for the unified hierarchy support, and agent for the
classic hierarchy support). We now always process events for these in the
following order:

  1. service notification messages  (SD_EVENT_PRIORITY_NORMAL-7)
  2. SIGCHLD signals (SD_EVENT_PRIORITY_NORMAL-6)
  3. cgroup inotify and cgroup agent (SD_EVENT_PRIORITY_NORMAL-5)

This is because when receiving SIGCHLD we invalidate PID information, which we
need to process the service notification messages which are bound to PIDs.
Hence the order between the first two items. And we want to process SIGCHLD
metadata to detect whether a service is gone, before using cgroup
notifications, to decide when a service is gone, since the former carries more
useful metadata.

Related to this:
https://bugs.freedesktop.org/show_bug.cgi?id=95264
https://github.com/systemd/systemd/issues/1961
2016-05-05 12:37:04 +02:00

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1.7 KiB
C

#pragma once
/***
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 "manager.h"
int bus_send_queued_message(Manager *m);
int bus_init(Manager *m, bool try_bus_connect);
void bus_done(Manager *m);
int bus_fdset_add_all(Manager *m, FDSet *fds);
void bus_track_serialize(sd_bus_track *t, FILE *f);
int bus_track_deserialize_item(char ***l, const char *line);
int bus_track_coldplug(Manager *m, sd_bus_track **t, char ***l);
int manager_sync_bus_names(Manager *m, sd_bus *bus);
int bus_foreach_bus(Manager *m, sd_bus_track *subscribed2, int (*send_message)(sd_bus *bus, void *userdata), void *userdata);
int bus_verify_manage_units_async(Manager *m, sd_bus_message *call, sd_bus_error *error);
int bus_verify_manage_unit_files_async(Manager *m, sd_bus_message *call, sd_bus_error *error);
int bus_verify_reload_daemon_async(Manager *m, sd_bus_message *call, sd_bus_error *error);
int bus_verify_set_environment_async(Manager *m, sd_bus_message *call, sd_bus_error *error);
int bus_forward_agent_released(Manager *m, const char *path);