6.1-RELEASE panic / lockmgr?

[Kris Kennaway]

On Fri, Jun 02, 2006 at 06:41:32PM +0200, Wilko Bulte wrote:
> On Thu, Jun 01, 2006 at 11:01:07PM +0100, Robert Watson wrote..
> > 
> > On Thu, 1 Jun 2006, Wilko Bulte wrote:
> > 
> > >My dual-CPU DS20 Alpha box can more or less consistently be
> > >forced into a panic like:
> > >
> > >FreeBSD/alpha (goldrush.wbnet) (ttyd0)^
> > >
> > >login: panic: lockmgr: thread 0xfffffc007d9d4a80, not exclusive lock holder
> > >0xfffffc006052d260 unlocking
> > >cpuid = 1
> > >KDB: enter: panic
> > >
> > >Trigger is a "make -j2 release".  j2 seems to be needed, not seen it with
> > >-j1
> > >
> > >Unfortunately after printing the line with "KDB" the whole thing appears 
> > >to become completely catatonic :(
> > 
> > Try putting a call to critical_enter() towards the beginning of panic(). 
> > Sometimes this increases the reliability of entering the debugger by 
> > avoiding interrupt delivery during the process of entering.  If you want to 
> > be able to continue out, you'll need a critical_exit() at the end, but that 
> > generally isn't helpful for panic().
> 
> Jay! ANother one, and this one entered the debugger alright:
> 
> racing pid 25497 tid 100147 td 0xfffffc004df56000
> kdb_enter() at kdb_enter+0x48
> panic() at panic+0x210
> lockmgr() at lockmgr+0x798
> vop_stdunlock() at vop_stdunlock+0x34
> VOP_UNLOCK_APV() at VOP_UNLOCK_APV+0x84
> vput() at vput+0xb4
> lookup() at lookup+0xd38
> namei() at namei+0x554
> do_execve() at do_execve+0x17c
> kern_execve() at kern_execve+0x160
> execve() at execve+0x60
> syscall() at syscall+0x438
> XentSys() at XentSys+0x64
> --- syscall (59, FreeBSD ELF64, execve) ---
> --- user mode ---
> db> 
> 
> How to proceed here?  I have 0 clue on lockmgr & friends :)

Enable DEBUG_VFS_LOCKS and DEBUG_LOCKS, then use 'show lockedvnods' to
find what other thread(s) is holding locks, and also trace them with
'tr <pid/tid>'

Kris
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