Debugging a system hang.

[Naoki]

Hey all,

I was asking this back over on fedora-list but had no responses.

How do I debug a hung system?  My box doesn't (ibm e326 with FC4,
x86_64) actually panic and crash so lkcd is of no use(?) kgdb? How about
magic sys key ?

I can reliably make it hang to a point where the only working operations
I can see are a blinking cursor and replies to ping packets.

I did see this message once :
<3>Debug : Sleeping function called from invalid context at
include/linux/rwsem.h:43
in_atomic:(0) irqs_disabled:(1)

Yes, I know it's off topic but I've googled and asked elsewhere to no
avail.