Not panic in nfsd (Re: panic in nfsd on 6.2-RC1)

[Sven Willenberger]

Sven Willenberger presumably uttered the following on 12/18/06 12:33:
> On Fri, 2006-12-15 at 23:20 +0200, Kostik Belousov wrote:
>> On Fri, Dec 15, 2006 at 02:29:58PM -0500, Kris Kennaway wrote:
> 
> <<SNIP>>
> 
>>>  
>>>> FWIW, I do see the following appearing in the /var/log/messages:
>>>> ufs_rename: fvp == tvp (can't happen) 
>>>> about once or twice a day, but cannot correlate those to lockup. Now
>>>> that I have enabled the options mentioned above in the kernel, I am
>>>> seeing some LOR issues:
>>>>
>>>> kernel: lock order reversal:
>>>> kernel: 1st 0xffffff00c3bab200 kqueue (kqueue) @ /usr/src/sys/kern/kern_event.c:1547
>>>> kernel: 2nd 0xffffff0005bb6078 struct mount mtx (struct mount mtx) @ /usr/src/sys/ufs/ufs/ufs_vnops.c:138
>>> OK, this is interesting, so let's proceed from here.
>>>
>>> Kris
>> Try this.
>>
>> Index: ufs/ufs/ufs_vnops.c
>> ===================================================================
>> RCS file: /usr/local/arch/ncvs/src/sys/ufs/ufs/ufs_vnops.c,v
>> retrieving revision 1.283
>> diff -u -r1.283 ufs_vnops.c
>> --- ufs/ufs/ufs_vnops.c	6 Nov 2006 13:42:09 -0000	1.283
>> +++ ufs/ufs/ufs_vnops.c	15 Dec 2006 21:19:51 -0000
>> @@ -133,19 +133,15 @@
>>  {
>>  	struct inode *ip;
>>  	struct timespec ts;
>> -	int mnt_locked;
>>  
>>  	ip = VTOI(vp);
>> -	mnt_locked = 0;
>> -	if ((vp->v_mount->mnt_flag & MNT_RDONLY) != 0) {
>> -		VI_LOCK(vp);
>> +	VI_LOCK(vp);
>> +	if ((vp->v_mount->mnt_flag & MNT_RDONLY) != 0)
>>  		goto out;
>> +	if ((ip->i_flag & (IN_ACCESS | IN_CHANGE | IN_UPDATE)) == 0) {
>> +		VI_UNLOCK(vp);
>> +		return;
>>  	}
>> -	MNT_ILOCK(vp->v_mount);		/* For reading of mnt_kern_flags. */
>> -	mnt_locked = 1;
>> -	VI_LOCK(vp);
>> -	if ((ip->i_flag & (IN_ACCESS | IN_CHANGE | IN_UPDATE)) == 0)
>> -		goto out_unl;
>>  
>>  	if ((vp->v_type == VBLK || vp->v_type == VCHR) && !DOINGSOFTDEP(vp))
>>  		ip->i_flag |= IN_LAZYMOD;
>> @@ -172,10 +168,7 @@
>>  
>>   out:
>>  	ip->i_flag &= ~(IN_ACCESS | IN_CHANGE | IN_UPDATE);
>> - out_unl:
>>  	VI_UNLOCK(vp);
>> -	if (mnt_locked)
>> -		MNT_IUNLOCK(vp->v_mount);
>>  }
>>  
>>  /*
> 
> 
> Patch applied cleanly (offset 6 lines), make buildworld, make kernel,
> reboot, make installworld, etc.
> 
> kernel: lock order reversal:
> kernel: 1st 0xffffff00b9181800 kqueue (kqueue) @ /usr/src/sys/kern/kern_event.c:1547
> kernel: 2nd 0xffffff00c16030d0 vnode interlock (vnode interlock) @ /usr/src/sys/ufs/ufs/ufs_vnops.c:132
> 
> 
> 
> _______________________________________________

Having enabled witness and ddb, etc I cannot get this LOR to trigger anymore, but
the machine is still locking up. I finally managed to get a piece of what was
appearing on the console which is the following (copied by hand by an onsite tech so
there may be a typo here and there):

--------cut--------------

bge_intr() at loge_intr+0x84a
ithread_loop() at ithread_loop+0x14c
fork_exit() at fork_exit+0xbb
fork_trampoline() at fork_trampoline+0xee
--- trap 0, rip-0, rsp-0xffffffffb371ad00, rbp-0 ---

Fatal trap 12: page fault while in Kernel Mode
cupid=1, apic id=01
fault virtual address - 0x28
fault code - supervisor write, page not present
instruction pointer - 0x8:0xffffffff801dae1a
stack pointer - 0x10:0xffffffffb371ab70
frame pointer - 0x10:0xffffffffb371abd0
code segment - base 0x0, limit 0xfffff, type 0x1b
		 - DPL 0, pres 1, long 1, def32 0, gram 1

processor eflags=interrupt enabled, resume, IOPL=0
current process=28 (irq 24:bge0)
trap number=12
panic: page fault
cupid=1

Uptime - 4d10h52m36s
Dumping 4031MB (2 chunks)
chunk0: 1MB (156 pages)... ok
chunk1: 4031MB (1031920)

----------cut-----------------

For some reason, by the time it reboots, there is no dump file available (even
though it is enabled in rc.conf and there is more than enough room in /var/crash to
hold it).

Sven