Bug 742546

Summary:	RFE: a better cycle breaking strategy
Product:	[Fedora] Fedora	Reporter:	Michal Schmidt <mschmidt>
Component:	systemd	Assignee:	systemd-maint
Status:	CLOSED WONTFIX	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	rawhide	CC:	dtardon, harald, herrold, johannbg, johannbg, john.ellson, lpoetter, metherid, mschmidt, plautrba, redhat
Target Milestone:	---
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Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:		Doc Type:	Bug Fix
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Clone Of:		Environment:
Last Closed:	2022-09-13 08:50:01 UTC	Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	784611, 871527

Description Michal Schmidt 2011-09-30 14:06:40 UTC

+++ This bug was initially created as a clone of Bug #741115 +++
[...]
--- Additional comment from john.ellson on 2011-09-29 13:08:44 EDT
Why doesn't systemd detect cycles like this?    It seems very fragile if this kind of bug in an unrelated service can make the system near unrecoverable because services like dbus and NetworkManager fail to start.

--- Additional comment from mschmidt on 2011-09-29 16:10:10 EDT

It does. It breaks cycles by dropping a (pretty much randomly selected) member of the cycle. In https://bugzilla.redhat.com/show_bug.cgi?id=741078#c3 I showed an example where dbus.socket was the unfortunate victim.

--- Additional comment from john.ellson on 2011-09-30 09:38:25 EDT

Isn't it a cycle in a directed graph?   Shouldn't the strategy be to drop the lowest node in the cycle, rather than a random node ?    Or perhaps drop the node with the least dependencies up to that point?

Somehow I think it should cause less damage than it did in this case.

Comment 1 Fedora Admin XMLRPC Client 2011-10-20 16:31:07 UTC

This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

Comment 2 Michal Schmidt 2012-06-07 14:58:55 UTC

Some cycle-breaking suggestions in the upstream mailing list thread:
http://lists.freedesktop.org/archives/systemd-devel/2012-May/005138.html

Comment 3 Fedora End Of Life 2013-01-16 17:41:35 UTC

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Comment 4 David Tardon 2022-09-13 08:50:01 UTC

Fedora is not the place where systemd development is happening. Please report your enhancement request to https://github.com/systemd/systemd/issues . Thank you for understanding.