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https://issues.apache.org/jira/browse/YUNIKORN-3416?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wilfred Spiegelenburg reassigned YUNIKORN-3416:
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Assignee: Wilfred Spiegelenburg
> UserGroupCache cleanup locks the singleton instead of the receiver; nil
> dereference after Stop()
> ------------------------------------------------------------------------------------------------
>
> Key: YUNIKORN-3416
> URL: https://issues.apache.org/jira/browse/YUNIKORN-3416
> Project: Apache YuniKorn
> Issue Type: Sub-task
> Components: core - common
> Reporter: Dale Richardson
> Assignee: Wilfred Spiegelenburg
> Priority: Minor
>
> {{cleanUpCache}} and {{resetCache}} lock the package-global {{instance}}
> while mutating the receiver's map {{c.ugs}}. In production the two are the
> same object, so the map is protected by accident. Where it goes wrong is
> {{Stop()}}: it sets {{instance = nil}}, and a cleaner run that has already
> picked its timer branch dereferences nil in {{cleanUpCache}}. That is a crash
> at shutdown (or on an in-process restart, YUNIKORN-3370). The non-singleton
> constructors are exported too, and such a cache mutates its map under a
> different cache's lock.
> Reproduced on the fork fix branch (the nil dereference and the non-singleton
> case both fail before the fix; the {{Stop()}} versus cleaner ordering shows
> under {{-race}}).
> Fix: lock the receiver ({{c.lock}}) in both functions. A fix exists on the
> tigerquoll fork ({{fix/usergroup-cache-receiver-locking}}, PR #18 there) and
> will be filed once this has a number. Not covered by it and left with
> YUNIKORN-3370: {{stopped}} is never cleared, and {{GetUserGroupCache}}'s
> {{return instance}} still races the nil write.
> Marker: three {{+checklocksignore}} sites in {{usergroup.go}} carry this
> JIRA; the fix removes them.
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