Re: nullfs broken on powerpc

On Wed, 25 Jan 2012 14:21:23 +0200
Kostik Belousov <kostikbel_at_gmail.com> wrote:

> On Tue, Jan 24, 2012 at 06:31:52PM +0100, Milan Obuch wrote:
> > Hi,
> > 

[ snip ]

> > This does not work with powerpc for me. With sources csup'ped this
> > morning, full system rebuild with GENERIC kernel, it is enough for
> > me to issue
> > 
> > mount_nullfs /data/src10 /usr/src
> > csup /usr/share/examples/cvsup/standard-supfile
> > 
> > and system panic occurs, with following on system console:
> > 
> > panic: mtx_lock() of spin mutex (null)
> > _at_ /usr/src/sys/kern/vfs_subr.c:2670 cpuid = 0
> > KDB: enter: panic
> > [ thread pid 1442 tid 100095 ]
> > Stopped at 0x40f734: addi r0, r0, 0x0
> > db>
> > 
> > At this point, I am able to interact with system, the question for
> > me is what I want to get from it :) I tried bt with following
> > result:
> > 
> > Tracing pid 1442 tid 100095 td 0x2d6b000
> > 0xe22c26d0: at panic+0x274
> > 0xe22c2730: at _mtx_lock_flags+0xc4
> > 0xe22c2760: at vgonel+0x330
> > 0xe22c27b0: at vrecycle+0x54
> > 0xe22c27d0: at null_inactive+0x30
> > 0xe22c27f0: at VOP_INACTIVE_APV+0xdc
> > 0xe22c2810: at vinactive+0x98
> > 0xe22c2850: at vputx+0x344
> > 0xe22c28a0: at vput+0x18
> > 0xe22c28c0: at kern_statat_vnhook+0x108
> > 0xe22c29d0: at kern_statat+0x18
> > 0xe22c29f0: at kern_lstat+0x2c
> > 0xe22c2a10: at sys_lstat+0x30
> > 0xe22c2a90: at trap+0x388
> > 0xe22c2b60: at powerpc_interrupt+0x108
> > 0xe22c2b90: user SC trap by _end+0x40d88c70: srr1=0xd032
> >             r1=0xffaf9a70 cr=0x28004044 xer=0x20000000
> > ctr=0x41a0ac40
> > db>
> > 
> > Does this shed any light for someone with more knowledge here? My
> > gut feeling is there is some endianness issue at play, the same
> > nullfs usage works for me flawlessly on both i386 and amd64
> > systems, so it could not be 32 vs 64 bit issue at least.
> > 
> > At line 2670 of /usr/src/sys/kern/vfs_subr.c I see end of function
> > void vgonel(struct vnode *vp)
> > 
> >         VI_LOCK(vp);
> >         vp->v_vnlock = &vp->v_lock;
> >         vp->v_op = &dead_vnodeops;
> >         vp->v_tag = "none";
> >         vp->v_type = VBAD;
> > }
> > 
> > so the question seems to be reduced to 'why is vp null?' or is my
> > small attempt on analyse flawed...

> I do not think that the vp is null. It more look like the *vp memory
> was zeroed. This has very low chances of being related to endianess,
> and more like a kernel memory corruption.
> 
> Take a dump and print the content of *vp.

How could I look into memory? I found page
http://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-online-ddb.html
and I can see registers (show reg), use x with absolute addresses, but
something like 'x vp' tells just 'Symbol not known' - should I somehow
load symbol table into memory? But backtrace shows function names... or
should I somehow modify GENERIC kernel to include more debugging info?
Kernel debugging is a bit new for me, even if I can write simple
modification into kernel, but only in some special (and narrow) area of
code...

Regards,
Milan