English Wikipedia, MediaWiki 1.23wmf10 (7a69cda)
From ~16:50 to ~17:40 today, many editors at [[Wikipedia:Village pump (technical)#Database error]] were reporting the following error when attempting to save articles:
A database query error has occurred. This may indicate a bug in the software.
Function: AbuseFilter::checkEmergencyDisable Error: 1205 Lock wait timeout exceeded; try restarting transaction (10.64.32.26)
The problem seems to have started with a bad edit to [[Special:AbuseFilter/554]] that caused it to match the majority of (or possibly even all) edits in the main namespace. The filter became flagged with "Warning: This filter was automatically disabled as a safety measure. It reached the limit of matching more than 5.00% of actions." (I'm not sure exactly when this flag appeared on the filter.)
The filter was not set to block edits, yet it appears the automatic disabling of it caused edits to be blocked anyway (with the above error).