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We'd call dns_resource_record_equal(), which calls dns_resource_key_equal()
internally, and then dns_resource_key_equal() a second time. Let's be
a bit smarter, and call dns_resource_key_equal() only once.
(before)
dns_resource_key_hash_func_count=514
dns_resource_key_compare_func_count=275
dns_resource_key_equal_count=62371
4.13s user 0.01s system 99% cpu 4.153 total
(after)
dns_resource_key_hash_func_count=514
dns_resource_key_compare_func_count=276
dns_resource_key_equal_count=31337
2.13s user 0.01s system 99% cpu 2.139 total
This doesn't necessarily make things faster, because we still spend more time
in dns_answer_add(), but it improves the compuational complexity of this part.
If we even make dns_resource_key_equal_faster, this will become worthwhile.
Run: systemctl show -a dbus.service | grep -E "SELinuxContext|AppArmorProfile|SmackProcessLabel"
Before patch:
SELinuxContext=[unprintable]
AppArmorProfile=[unprintable]
SmackProcessLabel=[unprintable]
After patch:
SELinuxContext=[""|"value of context"]
AppArmorProfile=[""|"value of context"]
SmackProcessLabel=[""|"value of context"]
lxc-create in semaphore sometimes fails with
ERROR: Unable to fetch GPG key from keyserver
Which often happens behind proxies. As the default key server is a load
balancer, retry a few times.
Also, cache the container image between runs, and only recreate it when
it is older than a week.
Same as with the other users, any non-trivial use of the objects requires
use from a single thread only or external locking. Using atomic operations
just for reference counts is not useful.
The sd-hwdb objects cannot be used concurrently from two threads in any
meaningful way, because query and iteration operations modify the object.
Thus atomic reference counts are pointless.
We had atomic counters, but all other operations were non-serialized. This
means that concurrent access to the bus object was only safe if _all_ threads
were doing read-only access. Even sending of messages from threads would not be
possible, because after sending of the message we usually want to remove it
from the send queue in the bus object, which would race. Let's just kill this.
The subvol snapshot logic doesn't cover sub-mounts either, and it really
shouldn't in the general case, hence let's simply stop at submounts in
all cases, both in the main and in the fall-back codepath.
As discussed here:
https://github.com/systemd/systemd/pull/11243#pullrequestreview-209477230
Before this commit bus messages had a single reference count: when it
reached zero the message would be freed. This simple approach meant a
cyclic dependency was typically seen: a message that was enqueued in a
bus connection object would reference the bus connection object but also
itself be referenced by the bus connection object. So far out strategy
to avoid cases like this was: make sure to process the bus connection
regularly so that messages don#t stay queued, and at exit flush/close
the connection so that the message queued would be emptied, and thus the
cyclic dependencies resolved. Im many cases this isn't done properly
however.
With this change, let's address the issue more systematically: let's
break the reference cycle. Specifically, there are now two types of
references to a bus message:
1. A regular one, which keeps both the message and the bus object it is
associated with pinned.
2. A "queue" reference, which is weaker: it pins the message, but not
the bus object it is associated with.
The idea is then that regular user handling uses regular references, but
when a message is enqueued on its connection, then this takes a "queue"
reference instead. This then means that a queued message doesn't imply
the connection itself remains pinned, only regular references to the
connection or a message associated with it do. Thus, if we end up in the
situation where a user allocates a bus and a message and enqueues the
latter in the former and drops all refs to both, then this will detect
this case and free both.
Note that this scheme isn't perfect, it only covers references between
messages and the busses they are associated with. If OTOH a bus message
is enqueued on a different bus than it is associated with cyclic deps
cannot be recognized with this simple algorithm, and thus if you enqueue
a message associated with a bus A on a bus B, and another message
associated with bus B on a bus A, a cyclic ref will be in effect and not
be discovered. However, given that this is an exotic case (though one
that happens, consider systemd-bus-stdio-bridge), it should be OK not to
cover with this, and people have to explicit flush all queues on exit in
that case.
Note that this commit only establishes the separate reference counters
per message. A follow-up commit will start making use of this from the
bus connection object.
