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Date:      Wed, 26 May 1999 18:39:05 +0400
From:      Dmitrij Tejblum <tejblum@arc.hq.cti.ru>
To:        "David E. Cross" <crossd@cs.rpi.edu>
Cc:        hackers@freebsd.org
Subject:   Re: kernel debugging assistance 
Message-ID:  <199905261439.SAA12649@arc.hq.cti.ru>
In-Reply-To: Your message of "Tue, 25 May 1999 21:09:02 EDT." <199905260109.VAA93769@cs.rpi.edu> 

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> I am trying to trace down the cause of the recursive lock and I stumbled upon
> this:
> 
> (kgdb) bt
> #0  boot (howto=256) at ../../kern/kern_shutdown.c:285
> #1  0xc014b3f4 in at_shutdown (
>     function=0xc0234aca <__set_sysuninit_set_sym_M_KTRACE_uninit_sys_uninit+154>, arg=0x10002, queue=-951064448) at ../../kern/kern_shutdown.c:446
> #2  0xc01470f8 in lockmgr (lkp=0xc10d8f00, flags=16842754, 
>     interlkp=0xc74fe8f0, p=0xc743eb20) at ../../kern/kern_lock.c:326
> #3  0xc016cfbc in vop_stdlock (ap=0xc7482a64) at ../../kern/vfs_default.c:209
> #4  0xc01e4fad in ufs_vnoperate (ap=0xc7482a64)
>     at ../../ufs/ufs/ufs_vnops.c:2299
> #5  0xc0175d97 in vn_lock (vp=0xc74fe880, flags=65538, p=0xc743eb20)
>     at vnode_if.h:811

[...]

> (kgdb) up 3
> #3  0xc016cfbc in vop_stdlock (ap=0xc7482a64) at ../../kern/vfs_default.c:209
> 209             return (lockmgr(l, ap->a_flags, &ap->a_vp->v_interlock, ap->a_p));
> (kgdb) print ap
> $1 = (struct vop_lock_args *) 0x0

This is just a glitch in gdb. The true value of ap is here:
> #3  0xc016cfbc in vop_stdlock (ap=0xc7482a64) at ../../kern/vfs_default.c:209
                                    ^^^^^^^^^^

I don't think that this dump is useful for debugging this problem. Perhaps, if 
you compile the kernel with DEBUG_LOCKS, you will get more useful info.

Dima




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