On Tue, 31 Jul 2001, John Baldwin wrote:
> >> On 31-Jul-01 Vincent Poy wrote:
> >> > On Tue, 31 Jul 2001, John Baldwin wrote:
> >> >> > root@pele [9:29pm][/usr/temp] >>
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: lock order reversal
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: lock order reversal
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: 1st 0xd92fea9c process lock @
> >> >> > /usr/src/sys/vm/vm_glue.c:469
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: 1st 0xd92fea9c process lock @
> >> >> > /usr/src/sys/vm/vm_glue.c:469
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: 2nd 0xc118dfb0 lockmgr
> >> >> > interlock
> >> >> > @ /usr/src/sys/kern/kern_lock.c:239
> >> >> > Jul 28 21:29:40 pele /boot/kernel/kernel: 2nd 0xc118dfb0 lockmgr
> >> >> > interlock
> >> >> > @ /usr/src/sys/kern/kern_lock.c:239
> >> >>
> >> >> This is due to the way that lockmgr locks are implemented unfortunately,
> >> >> and
> >> >> will be fixed when vm maps switch to sx locks instead of lockmgr locks.
> >> >
> >> > Interesting. Is there a workaround so it just reboots instead of
> >> > freezing? Also, I noticed that you committed some changes to the kernel,
> >> > is that supposed to help it any?
> >>
> >> There is currently not a workaround. The changes committed fix other
> >> things,
> >> but not this problem. I haven't actually seen this lock order cause a
> >> freeze
> >> before to be honest.
> >
> > Yeah, that's the weird part... I thought adding a DDB_UNATTENDED
> > as a option would atleast make it reboot or something...
>
> Well, since it is a lock order reversal, there is the chance of it
> resulting in a deadlock though the chances of that on a UP machine
> would be very, very rare indeed. The reversal in question is
> triggered when we swap a process out.
Yep, it's so rare that nothing can trigger it except for passwd
and chpass after they successfully exit and do the following
successfully...
passwd: updating the database...
passwd: done
Even vipw doesn't trigger it which I thought it would as it would
do all the users rather than just one.
Cheers,
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