Bug 14288

Summary:	BUG: bad unlock balance detected! trying to release lock (&futex_queues[i].lock)
Product:	Process Management	Reporter:	Rich Ercolani (rercola)
Component:	Other	Assignee:	process_other
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	akpm, dvhart
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.31	Subsystem:
Regression:	Yes	Bisected commit-id:
Attachments:	Verbose output of bad unlock balance

Description Rich Ercolani 2009-10-01 06:18:15 UTC

Created attachment 23216 [details]
Verbose output of bad unlock balance

I awoke after upgrading to 2.6.31 one day to find a blank screen.

After attaching and configuring a serial console for the next time it occurred, I got [attachment 1 [details]].

Never occurred prior to 2.6.31.

Comment 1 Darren Hart 2009-10-04 14:21:43 UTC

The bug was a result of the fault rework in e4dc5b7a36a49eff97050894cf1b3a9a02523717.  Thomas fixed it with 9694d494b7f462bffb86654fabe9e1ec2b2b0c47.  One of the retry_private optimization labels was placed after the double_lock_hb() instead of before it, leading to a double unlock on fault in wake_futex_op.