Lennart PoetteringandLukas Märdian
de90700f36
There's currently a deadlock between PID 1 and dbus-daemon: in some
cases dbus-daemon will do NSS lookups (which are blocking) at the same
time PID 1 synchronously blocks on some call to dbus-daemon. Let's break
that by setting SYSTEMD_NSS_DYNAMIC_BYPASS=1 env var for dbus-daemon,
which will disable synchronously blocking varlink calls from nss-systemd
to PID 1.
In the long run we should fix this differently: remove all synchronous
calls to dbus-daemon from PID 1. This is not trivial however: so far we
had the rule that synchronous calls from PID 1 to the dbus broker are OK
as long as they only go to interfaces implemented by the broke itself
rather than services reachable through it. Given that the relationship
between PID 1 and dbus is kinda special anyway, this was considered
acceptable for the sake of simplicity, since we quite often need
metadata about bus peers from the broker, and the asynchronous logic
would substantially complicate even the simplest method handlers.
This mostly reworks the existing code that sets SYSTEMD_NSS_BYPASS_BUS=
(which is a similar hack to deal with deadlocks between nss-systemd and
dbus-daemon itself) to set SYSTEMD_NSS_DYNAMIC_BYPASS=1 instead. No code
was checking SYSTEMD_NSS_BYPASS_BUS= anymore anyway, and it used to
solve a similar problem, hence it's an obvious piece of code to rework
like this.
Issue originally tracked down by Lukas Märdian. This patch is inspired
and closely based on his patch:
https://github.com/systemd/systemd/pull/22038
Fixes: #15316
Co-authored-by: Lukas Märdian <slyon@ubuntu.com>
System and Service Manager
Details
Most documentation is available on systemd's web site.
Assorted, older, general information about systemd can be found in the systemd Wiki.
Information about build requirements is provided in the README file.
Consult our NEWS file for information about what's new in the most recent systemd versions.
Please see the Code Map for information about this repository's layout and content.
Please see the Hacking guide for information on how to hack on systemd and test your modifications.
Please see our Contribution Guidelines for more information about filing GitHub Issues and posting GitHub Pull Requests.
When preparing patches for systemd, please follow our Coding Style Guidelines.
If you are looking for support, please contact our mailing list or join our IRC channel.
Stable branches with backported patches are available in the stable repo.