Date: Wed, 14 Nov 2001 09:16:26 -0800 (PST) From: David Wolfskill <david@catwhisker.org> To: current@freebsd.org Subject: lock order reversal for today's -CURRENT Message-ID: <200111141716.fAEHGQG33323@bunrab.catwhisker.org>
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Built & booted today's -CURRENT; saw the following on the console & in
/var/log/messages:
Nov 14 08:59:25 localhost /boot/kernel/kernel: lock order reversal
Nov 14 08:59:25 localhost /boot/kernel/kernel: 1st 0xc0427980 dev_pager create @ /usr/src/sys/vm/device_pager.c:143
Nov 14 08:59:25 localhost /boot/kernel/kernel: 2nd 0xc03feca0 pool mutex @ /usr/src/sys/kern/kern_sx.c:329
For device_pager.c (in dev_pager_alloc()):
/*
* Lock to prevent object creation race condition.
*/
sx_xlock(&dev_pager_sx);
/*
* Look up pager, creating as necessary.
*/
object = vm_pager_object_lookup(&dev_pager_object_list, handle);
For kern_sx.c (in _sx_assert()):
switch (what) {
case SX_LOCKED:
case SX_SLOCKED:
...
case SX_XLOCKED:
mtx_lock(sx->sx_lock);
if (sx->sx_xholder != curthread)
printf("Lock %s not exclusively locked @ %s:%d",
sx->sx_object.lo_name, file, line);
mtx_unlock(sx->sx_lock);
break;
default:
It's the SX_XLOCKED case that's of interest.
Sorry, I'm not clueful enough to do much with the code beyond this
"pointing & grunting". But I'm willing to test....
Running
FreeBSD m147.whistle.com 5.0-CURRENT FreeBSD 5.0-CURRENT #172: Wed Nov 14 08:37:20 PST 2001 root@localhost:/common/S3/obj/usr/src/sys/LAPTOP_30W i386
Recent CVSup history:
freebeast[1] tail /var/log/cvsup-history.log
CVSup begin from cvsup14.freebsd.org at Sat Nov 10 03:47:00 PST 2001
CVSup ended from cvsup14.freebsd.org at Sat Nov 10 03:54:07 PST 2001
CVSup begin from cvsup14.freebsd.org at Sun Nov 11 03:47:00 PST 2001
CVSup ended from cvsup14.freebsd.org at Sun Nov 11 03:52:55 PST 2001
CVSup begin from cvsup14.freebsd.org at Mon Nov 12 03:47:00 PST 2001
CVSup ended from cvsup14.freebsd.org at Mon Nov 12 03:52:53 PST 2001
CVSup begin from cvsup14.freebsd.org at Tue Nov 13 03:47:00 PST 2001
CVSup ended from cvsup14.freebsd.org at Tue Nov 13 03:53:11 PST 2001
CVSup begin from cvsup14.freebsd.org at Wed Nov 14 03:47:00 PST 2001
CVSup ended from cvsup14.freebsd.org at Wed Nov 14 03:53:08 PST 2001
(I haven't built much on freebeast today; tried tinkering with BIOS
options & made the machine unstable enough that it crashed during the
-STABLE buildworld twice this morning. I need to wait 'til I can
borrow my spouse's PC monitor to undo that damage. Meanwhile, what I
report above is happening on the laptop.)
Cheers,
david
--
David H. Wolfskill david@catwhisker.org
As a computing professional, I believe it would be unethical for me to
advise, recommend, or support the use (save possibly for personal
amusement) of any product that is or depends on any Microsoft product.
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