Bug 7792

Summary:	"modprobe -r ohci1394" may block uninterruptibly
Product:	Drivers	Reporter:	Stefan Richter (stefanr)
Component:	IEEE1394	Assignee:	Stefan Richter (stefanr)
Status:	CLOSED CODE_FIX
Severity:	low
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.20-rc3	Subsystem:
Regression:	---	Bisected commit-id:
Bug Depends on:
Bug Blocks:	7550
Attachments:	ieee1394: fix another deadlock in nodemgr

Description Stefan Richter 2007-01-08 12:54:24 UTC

Most recent kernel where this bug did *NOT* occur: unknown
Hardware Environment: UP PC with two FireWire cards, one card has an external
FireWire node attached
Steps to reproduce: for ((x=0; x<20; x++));do modprobe ohci1394 && sleep 2 &&
modprobe -r ohci1394 || break; done

modprobe -r will soon get stuck in D state, hanging on kthread_stop with
hl_drivers_sem and kthread_stop_lock held. But different to bug 6706, knodemgrd
sleeps *interruptibly* in nodemgr_host_thread. As soon as the external node is
unplugged, modprobe gets going again. I.e. the bug can be recovered from with
physical access to the machine.

I cannot reproduce this _without_ an external node attached.

Comment 1 Stefan Richter 2007-01-08 12:56:39 UTC

PS: This was an uniprocessor kernel, configured without kernel preemption.

Comment 2 Stefan Richter 2007-01-08 13:09:45 UTC

Als happens on UP PC with SMP PREEMPT kernel.

Comment 3 Stefan Richter 2007-02-10 13:00:10 UTC

Created attachment 10376 [details]
ieee1394: fix another deadlock in nodemgr

Comment 4 Stefan Richter 2007-02-21 03:27:12 UTC

fix is in 2.6.21-rc1