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This patch set adds full support the new unified cgroup hierarchy logic
of modern kernels.
A new kernel command line option "systemd.unified_cgroup_hierarchy=1" is
added. If specified the unified hierarchy is mounted to /sys/fs/cgroup
instead of a tmpfs. No further hierarchies are mounted. The kernel
command line option defaults to off. We can turn it on by default as
soon as the kernel's APIs regarding this are stabilized (but even then
downstream distros might want to turn this off, as this will break any
tools that access cgroupfs directly).
It is possibly to choose for each boot individually whether the unified
or the legacy hierarchy is used. nspawn will by default provide the
legacy hierarchy to containers if the host is using it, and the unified
otherwise. However it is possible to run containers with the unified
hierarchy on a legacy host and vice versa, by setting the
$UNIFIED_CGROUP_HIERARCHY environment variable for nspawn to 1 or 0,
respectively.
The unified hierarchy provides reliable cgroup empty notifications for
the first time, via inotify. To make use of this we maintain one
manager-wide inotify fd, and each cgroup to it.
This patch also removes cg_delete() which is unused now.
On kernel 4.2 only the "memory" controller is compatible with the
unified hierarchy, hence that's the only controller systemd exposes when
booted in unified heirarchy mode.
This introduces a new enum for enumerating supported controllers, plus a
related enum for the mask bits mapping to it. The core is changed to
make use of this everywhere.
This moves PID 1 into a new "init.scope" implicit scope unit in the root
slice. This is necessary since on the unified hierarchy cgroups may
either contain subgroups or processes but not both. PID 1 hence has to
move out of the root cgroup (strictly speaking the root cgroup is the
only one where processes and subgroups are still allowed, but in order
to support containers nicey, we move PID 1 into the new scope in all
cases.) This new unit is also used on legacy hierarchy setups. It's
actually pretty useful on all systems, as it can then be used to filter
journal messages coming from PID 1, and so on.
The root slice ("-.slice") is now implicitly created and started (and
does not require a unit file on disk anymore), since
that's where "init.scope" is located and the slice needs to be started
before the scope can.
To check whether we are in unified or legacy hierarchy mode we use
statfs() on /sys/fs/cgroup. If the .f_type field reports tmpfs we are in
legacy mode, if it reports cgroupfs we are in unified mode.
This patch set carefuly makes sure that cgls and cgtop continue to work
as desired.
When invoking nspawn as a service it will implicitly create two
subcgroups in the cgroup it is using, one to move the nspawn process
into, the other to move the actual container processes into. This is
done because of the requirement that cgroups may either contain
processes or other subgroups.
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The result of unit_get_sibling_mask returns bits for the sibling cgroups
even if they are not supported in the local system.
I caught this on a machine where my kernel was misconfigured with
CONFIG_MEMCG unset, but the rest of the cgroup infrastructure enabled.
Tested with `make check` on a host running a kernel where CONFIG_MEMCG
is not set.
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It's primarily just a property of the Manager object after all, and we
try to refer to PID 1 as "manager" instead of "systemd", hence let's to
stick to this here too.
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This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.
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The asserts used in the tests should never be allowed to be
optimized away
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Commit 637f421e5c6a ("cgroups: always propagate controller membership
to siblings") changed the mask propagation logic, but the test wasn't
updated.
Move to normal tests from manual tests, it should not touch the system
anymore.
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It seems that unit_get_siblings_mask returns the controllers
filtered by what is available, but get_members_mask and
get_cgroup_mask do not. This just fixes the test following the
symptoms.
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Also add a bit of debugging output to help diagnose problems,
add missing units, and simplify cppflags.
Move test-engine to normal tests from manual tests, it should now
work without destroying the system.
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If -flto is used then gcc will generate a lot more warnings than before,
among them a number of use-without-initialization warnings. Most of them
without are false positives, but let's make them go away, because it
doesn't really matter.
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Previously a cgroup setting down tree would result in cgroup membership
additions being propagated up the tree and to the siblings, however a
unit could never lose cgroup memberships again. With this change we'll
make sure that both cgroup additions and removals propagate properly.
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The static analyzer scan-build had a few issues with analysing
parts of systemd.
gpt-auto-generator.c:
scan-build could not find blkid.h. Whether it should be blkid.h or
blkid/blkid.h seems to depend on the version used. We already use
blkid/blkid.h in udev-builtin-blkid.c so it seems safe to use that
here too.
Makefile.am:
Moved some -D's from CFLAGS to CPPFLAGS. I also simplified them a
bit and got rid of a left over DBUS_CFLAGS.
test-cgroup-mask.c/test-sched-prio.c
A variable was added to store the replaced TEST_DIR. When wrapped
in an assert_se TEST_DIR was not replaced in the logged error.
While not an issue introduced in this patch we might as well fix
it up while we are here.
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