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The Barrier-API simplifies cross-fork() synchronization a lot. Replace the
hard-coded eventfd-util implementation and drop it.
Compared to the old API, Barriers also handle exit() of the remote side as
abortion. This way, segfaults will not cause the parent to deadlock.
EINTR handling is currently ignored for any barrier-waits. This can easily
be added, but it isn't needed so far so I dropped it. EINTR handling in
general is ugly, anyway. You need to deal with pselect/ppoll/... variants
and make sure not to unblock signals at the wrong times. So genrally,
there's little use in adding it.
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The "Barrier" object is a simple inter-process barrier implementation. It
allows placing synchronization points and waiting for the other side to
reach it. Additionally, it has an abortion-mechanism as second-layer
synchronization to send abortion-events asynchronously to the other side.
The API is usually used to synchronize processes during fork(). However,
it can be extended to pass state through execve() so you could synchronize
beyond execve().
Usually, it's used like this (error-handling replaced by assert() for
simplicity):
Barrier b;
r = barrier_init(&b);
assert_se(r >= 0);
pid = fork();
assert_se(pid >= 0);
if (pid == 0) {
barrier_set_role(&b, BARRIER_CHILD);
...do child post-setup...
if (CHILD_SETUP_FAILED)
exit(1);
...child setup done...
barrier_place(&b);
if (!barrier_sync(&b)) {
/* parent setup failed */
exit(1);
}
barrier_destroy(&b); /* redundant as execve() and exit() imply this */
/* parent & child setup successful */
execve(...);
}
barrier_set_role(&b, BARRIER_PARENT);
...do parent post-setup...
if (PARENT_SETUP_FAILED) {
barrier_abort(&b); /* send abortion event */
barrier_wait_abortion(&b); /* wait for child to abort (exit() implies abortion) */
barrier_destroy(&b);
...bail out...
}
...parent setup done...
barrier_place(&b);
if (!barrier_sync(&b)) {
...child setup failed... ;
barrier_destroy(&b);
...bail out...
}
barrier_destroy(&b);
...child setup successfull...
This is the most basic API. Using barrier_place() to place barriers and
barrier_sync() to perform a full synchronization between both processes.
barrier_abort() places an abortion barrier which superceeds any other
barriers, exit() (or barrier_destroy()) places an abortion-barrier that
queues behind existing barriers (thus *not* replacing existing barriers
unlike barrier_abort()).
This example uses hard-synchronization with wait_abortion(), sync() and
friends. These are all optional. Barriers are highly dynamic and can be
used for one-way synchronization or even no synchronization at all
(postponing it for later). The sync() call performs a full two-way
synchronization.
The API is documented and should be fairly self-explanatory. A test-suite
shows some special semantics regarding abortion, wait_next() and exit().
Internally, barriers use two eventfds and a pipe. The pipe is used to
detect exit()s of the remote side as eventfds do not allow that. The
eventfds are used to place barriers, one for each side. Barriers itself
are numbered, but the numbers are reused once both sides reached the same
barrier, thus you cannot address barriers by the index. Moreover, the
numbering is implicit and we only store a counter. This makes the
implementation itself very lightweight, which is probably negligible
considering that we need 3 FDs for a barrier..
Last but not least: This barrier implementation is quite heavy. It's
definitely not meant for fast IPC synchronization. However, it's very easy
to use. And given the *HUGE* overhead of fork(), the barrier-overhead
should be negligible.
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One missing string found.
A few things had to be moved around to make it possible to test them.
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If we want to avoid reading a totally empty file, it seems better
to check after we have opened the file, not before.
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Special care is needed so that we get an error message if the
file failed to parse, but not when it is missing. To avoid duplicating
the same error check in every caller, add an additional 'warn' boolean
to tell config_parse whether a message should be issued.
This makes things both shorter and more robust wrt. to error reporting.
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Now we are getting into kernel < 3.4 territory...
https://bugs.freedesktop.org/show_bug.cgi?id=80095
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Was: Failed to listen on [::]:2000: Success
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records
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Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.
(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)
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Turns out, making strings shell-proof is harder than expected:
# machinectl set-hostname "foo|poweroff" && . /etc/machine-info
(This could be simplified by quoting *and* escaping all characters,
which is harmless in shell but unnecessary.)
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We already encourage upstreams to keep the default configuration
separate from user customizations for software that is installed in
the system location. Let's allow that separation also for software
that is installed in the home directory.
Some discussion:
http://thread.gmane.org/gmane.comp.sysutils.systemd.devel/19627
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We use "typedef struct Ring Ring" with camel-case for internal objects.
So rename "struct ring" to "Ring".
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This is like MIN but evaluates 3 arguments. We already have MAX3, so add
the equivalent for MIN.
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Let's always stick to glibc's way to determine byte order, and not mix
autoconf-specific checks with gcc checks.
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private in-addr-util.[ch]
These are enough calls for a new file, and they are sufficiently
different from the sockaddr-related calls, hence let's split this out.
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make use of it from machined
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xxx,x-systemd.default-timeout=y,zzz was filtered to xxxzzz,
but should be xxx,zzz, of course.
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ConditionFirstBoot= instead
As Zbigniew pointed out a new ConditionFirstBoot= appears like the nicer
way to hook in systemd-firstboot.service on first boots (those with /etc
unpopulated), so let's do this, and get rid of the generator again.
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NULSTR_FOREACH() looks for a terminating zero and the element also needs
one.
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or when creating OS images offline
A new tool "systemd-firstboot" can be used either interactively on boot,
where it will query basic locale, timezone, hostname, root password
information and set it. Or it can be used non-interactively from the
command line when prepareing disk images for booting. When used
non-inertactively the tool can either copy settings from the host, or
take settings on the command line.
$ systemd-firstboot --root=/path/to/my/new/root --copy-locale --copy-root-password --hostname=waldi
The tool will be automatically invoked (interactively) now on first boot
if /etc is found unpopulated.
This also creates the infrastructure for generators to be notified via
an environment variable whether they are running on the first boot, or
not.
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Instead, take a list of exceptions to our usual CC check
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This way we can reuse it other code thatn just localectl/localed +
timedatectl/timedated.
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Let's better be safe than sorry.
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the only correct name appears to be "crisv32"...
http://lists.freedesktop.org/archives/systemd-devel/2014-July/020899.html
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I don't have suitable hardware at hand, so this is based
on debian documentation:
https://wiki.debian.org/ArmEabiPort#GCC_preprocessor_macros_for_floating_point
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This is really just about library locations, hence clarify that we don't
assume this to be anything but that.
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We should follow the naming scheme waitid() uses, not come up with our
own reversed one...
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This does the inverse of RestartPreventExitStatus=: it forces a restart
of a service when a certain exit status is returned by a service
process.
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systemctl -H root@foobar:waldi
will now show a list of services running on container "waldi" on host
"foobar", using "root" for authenticating at "foobar".
Since entereing a container requires priviliges, this will only work
correctly for root logins.
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