If the helper is reparented to init before it gets ppid() then in certain circumstances it will loop forever while holding the mutex, even though its original parent is long gone. This can happen if the helper is started just as the parent is killed during shutdown.
Created attachment 12332 [details]
Patch for 4.5rc
Please apply to 4.5 after BZ12110 - applying in BZ number order is easiest :-)
Here are patches for v4-5.
Pushed to autobuild-v4-5-test.
(In reply to Karolin Seeger from comment #3)
Pushed to v4-5-test.
Closing out bug report.