This macro will read a pointer of any type, return it, and set the
pointer to NULL. This is useful as an explicit concept of passing
ownership of a memory area between pointers.
This takes inspiration from Rust:
https://doc.rust-lang.org/std/option/enum.Option.html#method.take
and was suggested by Alan Jenkins (@sourcejedi).
It drops ~160 lines of code from our codebase, which makes me like it.
Also, I think it clarifies passing of ownership, and thus helps
readability a bit (at least for the initiated who know the new macro)
We maintain a queue of units and jobs that we are supposed to generate
change/new notifications for because they were either just created or
some of their property has changed. Let's throttle processing of this
queue a bit: as soon as > 1K of bus messages are queued for writing
let's skip processing the queue, and then recheck on the next
iteration again.
Moreover, never process more than 100 units in one go, return to the
event loop after that. Both limits together should put effective limits
on both space and time usage of the function, delaying further
operations until a later moment, when the queue is empty or the the
event loop is sufficiently idle again.
This should keep the number of generated messages much lower than
before on busy systems or where some client is hanging.
Note that this also means a bad client can slow down message dispatching
substantially for up to 90s if it likes to, for all clients. But that
should be acceptable as we only allow trusted bus clients, anyway.
Fixes: #8166
This is an optimization: there's no point in enqueuing unit and job
change notificiation signal messages into bus connection that aren't
fully set up yet.
This doesn't fix#8166 but should lower the load of messages enqueued
but not processed yet a bit.
This corrects the control flow: when we reuse the API bus as system bus,
let's definitely invoke bus_init_system() too, so that it is called
regardless how we acquired the bus object.
(Note that this doesn't actually change anything, as we only inherit the
bus like this in system mode, and bus_init_system() doesn't do anything
in system bus, besides writing a log message)
Let's better be safe than sorry, and validate that api_bus is not NULL
before we send messages to it. Of course, strictly speaking this
shouldn't actually be necessary, as the tracker object should not exist
without the bus, but let's be extra sure.
Previously, we'd synchronize bus names immediately when we succeeded
connecting to the bus, potentially even before coldplugging the units.
This was problematic, as synchronizing bus names meant invoking the
per-unit name change handler function which might change the unit's
state — which will result in consistency when done before we coldplug
things.
With this change we instead enqueue a job for the event loop to resync
the names in a later loop iteration, i.e. at a point where we know
coldplugging has finished.
This removes the current bus_init() call, as it had multiple problems:
it munged handling of the three bus connections we care about (private,
"api" and system) into one, even though the conditions when which was
ready are very different. It also added redundant logging, as the
individual calls it called all logged on their own anyway.
The three calls bus_init_api(), bus_init_private() and bus_init_system()
are now made public. A new call manager_dbus_is_running() is added that
works much like manager_journal_is_running() and is a lot more careful
when checking whether dbus is around. Optionally it checks the unit's
deserialized_state rather than state, in order to accomodate for cases
where we cant to connect to the bus before deserializing the
"subscribed" list, before coldplugging the units.
manager_recheck_dbus() is added, that works a lot like
manager_recheck_journal() and is invoked in unit_notify(), i.e. when
units change state.
All in all this should make handling a bit more alike to journal
handling, and it also fixes one major bug: when running in user mode
we'll now connect to the system bus early on, without conditionalizing
this in anyway.
log.h really should only include the bare minimum of other headers, as
it is really pulled into pretty much everything else and already in
itself one of the most basic pieces of code we have.
Let's hence drop inclusion of:
1. sd-id128.h because it's entirely unneeded in current log.h
2. errno.h, dito.
3. sys/signalfd.h which we can replace by a simple struct forward
declaration
4. process-util.h which was needed for getpid_cached() which we now hide
in a funciton log_emergency_level() instead, which nicely abstracts
the details away.
5. sys/socket.h which was needed for struct iovec, but a simple struct
forward declaration suffices for that too.
Ultimately this actually makes our source tree larger (since users of
the functionality above must now include it themselves, log.h won't do
that for them), but I think it helps to untangle our web of includes a
tiny bit.
(Background: I'd like to isolate the generic bits of src/basic/ enough
so that we can do a git submodule import into casync for it)
The aim of this change is to make sure that we properly log about all
D-Bus connection problems. After all, we only ever attempt to get on the
bus if dbus-daemon is around, so any failure in the process should be
treated as an error.
bus_init_system() is only called from bus_init() and in
bus_init() we have a bool flag which governs whether we should attempt
to connect to the system bus or not.
Hence if we are in bus_init_system() then it is clear we got called from
a context where connection to the bus is actually required and therefore
shouldn't be treated as the "best effort" type of operation. Same
applies to bus_init_api().
We make use of those error codes in bus_init() and log high level
message that informs admin about what is going on (and is easy to spot
and makes sense to an end user).
Also "retrying later" bit is actually a lie. We won't retry unless we
are explicitly told to reconnect via SIGUSR1 or re-executed. This is
because bus_init() is always called from the context where dbus-daemon
is already around and hence bus_init() won't be called again from
unit_notify().
Fixes#7782
This way, clients can install the very same match on direct and broker
connections as in both cases the messages will originate from the o.f.s1
service.
Let's remove a number of synchronization points from our service
startups: let's drop synchronous match installation, and let's opt for
asynchronous instead.
Also, let's use sd_bus_match_signal() instead of sd_bus_add_match()
where we can.
We'd like to use inotify to get notified when AF_UNIX sockets become
connectable. That happens at the moment of listen(), but this is doesn't
necessarily create in a watchable inotify event. Hence, let's synthesize
one whenever we generically create a socket, or when we know we created
it for a D-Bus server.
Ideally we wouldn't have to do this, and the kernel would generate an
event anyway for this. Doing this explicitly isn't too bad however, as
the event is still nicely associated with the AF_UNIX socket node, and
we generate all D-Bus sockets in our code hence it's safe.
The advantage is that is the name is mispellt, cpp will warn us.
$ git grep -Ee "conf.set\('(HAVE|ENABLE)_" -l|xargs sed -r -i "s/conf.set\('(HAVE|ENABLE)_/conf.set10('\1_/"
$ git grep -Ee '#ifn?def (HAVE|ENABLE)' -l|xargs sed -r -i 's/#ifdef (HAVE|ENABLE)/#if \1/; s/#ifndef (HAVE|ENABLE)/#if ! \1/;'
$ git grep -Ee 'if.*defined\(HAVE' -l|xargs sed -i -r 's/defined\((HAVE_[A-Z0-9_]*)\)/\1/g'
$ git grep -Ee 'if.*defined\(ENABLE' -l|xargs sed -i -r 's/defined\((ENABLE_[A-Z0-9_]*)\)/\1/g'
+ manual changes to meson.build
squash! build-sys: use #if Y instead of #ifdef Y everywhere
v2:
- fix incorrect setting of HAVE_LIBIDN2
If dbus is already down during shutdown, we can't propagate the cgroup
release message anymore, but that's expected and nothing to warn about.
Hence let's downgrade the message from LOG_WARN to LOG_DEBUG.
Fixes: #6777
This moves pretty much all uses of getpid() over to getpid_raw(). I
didn't specifically check whether the optimization is worth it for each
replacement, but in order to keep things simple and systematic I
switched over everything at once.
manager_sync_bus_names() function retrieves the dbus names
and compares it with unit bus names. It could be right
after the list is retrieved, the dbus peer is disconnected.
In this case it is really not an ERROR print if
sd_bus_get_name_creds() or sd_bus_creds_get_unique_name()
fail.
src/core/dbus.c: In function 'find_unit':
src/core/dbus.c:334:15: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
*unit = u;
^
src/core/dbus.c:301:15: note: 'u' was declared here
Unit *u;
^
Let's make semantics of this field more similar to the same functionality in
the Unit object, in particular as we add new functionality to it later on.
This adds two (privileged) bus calls Ref() and Unref() to the Unit interface.
The two calls may be used by clients to pin a unit into memory, so that various
runtime properties aren't flushed out by the automatic GC. This is necessary
to permit clients to race-freely acquire runtime results (such as process exit
status/code or accumulated CPU time) on successful service termination.
Ref() and Unref() are fully recursive, hence act like the usual reference
counting concept in C. Taking a reference is a privileged operation, as this
allows pinning units into memory which consumes resources.
Transient units may also gain a reference at the time of creation, via the new
AddRef property (that is only defined for transient units at the time of
creation).
The macro determines the right length of a AF_UNIX "struct sockaddr_un" to pass to
connect() or bind(). It automatically figures out if the socket refers to an
abstract namespace socket, or a socket in the file system, and properly handles
the full length of the path field.
This macro is not only safer, but also simpler to use, than the usual
offsetof() + strlen() logic.
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=95264https://github.com/systemd/systemd/issues/1961
Previously, we had two enums ManagerRunningAs and UnitFileScope, that were
mostly identical and converted from one to the other all the time. The latter
had one more value UNIT_FILE_GLOBAL however.
Let's simplify things, and remove ManagerRunningAs and replace it by
UnitFileScope everywhere, thus making the translation unnecessary. Introduce
two new macros MANAGER_IS_SYSTEM() and MANAGER_IS_USER() to simplify checking
if we are running in one or the user context.
When the daemon reloads, it doesn not actually give up its DBus connection,
as wrongly stated in an earlier commit. However, even though the bus
connection stays open, the daemon flushes out all its internal state.
Hence, if there is a NameOwnerChanged signal after the flush and before the
deserialization, it cannot be matched against any pending unit.
To fix this, rename bus_list_names() to manager_sync_bus_names() and call
it explicitly at the end of the daemon reload operation.
During daemon-reload, PID1 temporarly loses its DBus connection, so there's
a small window in which all signals sent by dbus-daemon are lost.
This is a problem, since we rely on the NameOwnerChanged signals in order to
consider a service with Type=dbus fully started or terminated, respectively.
In order to fix this, a rewrite of bus_list_names() is necessary. We used
to walk the current list of names on the bus, and blindly triggered the
bus_name_owner_change() callback on each service, providing the actual name
as current owner. This implementation has a number of problems:
* We cannot detect if the the name was moved from one owner to the other
while we were reloading
* We don't notify services which missed the name loss signal
* Providing the actual name as current owner is a hack, as the comment also
admits.
To fix this, this patch carries the following changes:
* Track the name of the current bus name owner, and (de-)serialize it
during reload. This way, we can detect changes.
* In bus_list_names(), walk the list of bus names we're interested in
first, and then see if the name is active on the bus. If it is,
check it it's still the same as it used to be, and synthesize
NameOwnerChanged signals for the name add and/or loss.
This should fully synchronize the current name list with the internal
state of all services.
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
Now that we don't have RequiresOverridable= and RequisiteOverridable=
dependencies anymore, we can get rid of tracking the "override" boolean
for jobs in the job engine, as it serves no purpose anymore.
While we are at it, fix some error messages we print when invoking
functions that take the override parameter.
There are more than enough calls doing string manipulations to deserve
its own files, hence do something about it.
This patch also sorts the #include blocks of all files that needed to be
updated, according to the sorting suggestions from CODING_STYLE. Since
pretty much every file needs our string manipulation functions this
effectively means that most files have sorted #include blocks now.
Also touches a few unrelated include files.
Let's use strjoina() rather than strjoin() for construct dbus match
strings.
Also, while we are at it, fix parameter ordering, so that our functions
always put the object first, like it is customary for OO-like
programming.
The following details are passed:
- unit: the primary name of the unit upon which the action was
invoked (i.e. after resolving any aliases);
- verb: one of 'start', 'stop', 'reload', 'restart', 'try-restart',
'reload-or-restart', 'reload-or-try-restart', 'kill',
'reset-failed', or 'set-property', corresponding to the
systemctl verb used to invoke the action.
Typical use of these details in a polkit policy rule might be:
// Allow alice to manage example.service;
// fall back to implicit authorization otherwise.
polkit.addRule(function(action, subject) {
if (action.id == "org.freedesktop.systemd1.manage-units" &&
action.lookup("unit") == "example.service" &&
subject.user == "alice") {
return polkit.Result.YES;
}
});
We also supply a custom polkit message that includes the unit's name and
the requested operation.
Extra details for an action can be supplied when calling polkit's
CheckAuthorization method. Details are a list of key/value string pairs.
Custom policy can use these details when making authorization decisions.
Let's add a way to get the type-specific D-Bus interface of a unit from
either its type or name to src/basic/unit-name.[ch]. That way we can
share it with the client side, where it is useful in tools like cgls or
machinectl.
Also ports over machinectl to make use of this.
Lennart Poettering