linux-kernel - Re: 2.6.33.5 rt23: machine lockup (nfs/autofs related?)

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Date:	Mon, 12 Jul 2010 20:06:21 -0700
From:	Fernando Lopez-Lezcano <nando@...ma.Stanford.EDU>
To:	john stultz <johnstul@...ibm.com>
Cc:	nando@...ma.Stanford.EDU, Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: 2.6.33.5 rt23: machine lockup (nfs/autofs related?)

On Mon, 2010-07-12 at 18:40 -0700, john stultz wrote:
> On Mon, 2010-07-12 at 18:10 -0700, Fernando Lopez-Lezcano wrote:
> > On Mon, 2010-07-12 at 16:53 -0700, john stultz wrote:
> > > 
> > > Hrm. Ok.. I think the line 2100 above gives us a hint: (aparent == anon)
> > > So if that were the case, we would have already locked aparent and that
> > > would explain the blowup.
> > > 
> > > How does it do with the following change?
> > 
> > Ok, you are on to something. The machine did not crash hard!
> > But the serial console printed this:
> 
> Sigh. Its never easy, is it? :)

Hardly ever .... :-)
I have _read_ about stories of stuff being solved on the first try, ha.

> > --------
> > BUG: unable to handle kernel NULL pointer dereference at 0000008c
> > IP: [<c045e50a>] rt_spin_lock_fastunlock.clone.2+0x6/0x3e
> ...
> > Pid: 2855, comm: nautilus Not tainted
> > 2.6.33.6-147.rt23.3.fc12.ccrma.i686.rt #3 P5K/EPU/P5K/EPU
> > EIP: 0060:[<c045e50a>] EFLAGS: 00210246 CPU: 0
> > EIP is at rt_spin_lock_fastunlock.clone.2+0x6/0x3e
> > EAX: 00000078 EBX: ef45393c ECX: 00000000 EDX: 00000078
> > ESI: ef716edc EDI: 00000000 EBP: f1977c8c ESP: f1977c88
> >  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 preempt:00000000
> > Process nautilus (pid: 2855, ti=f1976000 task=f2347130 task.ti=f1976000)
> > Stack:
> >  ef45393c f1977c94 c0781206 f1977cc8 c04d842e 00000000 ef703e54 faadd5bc
> > <0> f1977cdc 126bc87a ef703ddc 00000000 ef45393c ef716edc ef6f5494
> > faafdc6c
> > <0> f1977df8 faad9041 c3604b5c faafdc6c ef452bfc 00007e7f f5eb41e8
> > 00000007
> > Call Trace:
> >  [<c0781206>] ? rt_spin_unlock+0x8/0xa
> >  [<c04d842e>] ? d_materialise_unique+0x210/0x2aa
> 
> Can you gdb list *0xc04d842e ?

(gdb) list *0xc04d842e
0xc04d842e is in d_materialise_unique (fs/dcache.c:2073).
2068	out_unalias:
2069		d_move_locked(alias, dentry);
2070		ret = alias;
2071	out_err:
2072		spin_unlock(&inode->i_lock);
2073		if (m2)
2074			mutex_unlock(m2);
2075		if (m1)
2076			mutex_unlock(m1);
2077		return ret;

> Thanks again for all the testing here! Its really appreciated!

No problem, not the first time (but it had been a while...)
-- Fernando


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