Re: [2.6.30-rc1] RCU detected CPU 1 stall

[Al Viro <viro@ZenIV.linux.org.uk>]

On Fri, Apr 10, 2009 at 04:12:45PM -0700, Paul E. McKenney wrote:
> On Sat, Apr 11, 2009 at 06:08:54AM +0900, Tetsuo Handa wrote:
> > Hello.
> > 
> > Paul E. McKenney wrote:
> > > Tetsuo, how many tasks did you have on this machine?
> > I didn't count how many tasks were running on this machine.
> > But the number of tasks should be very low, for this happened during
> > the boot stage of Debian Sarge.
> > 
> > 30 seconds ago from the first stalled message
> > 
> > [   41.415158] INFO: RCU detected CPU 1 stall (t=4294902646/2500 jiffies)
> > [   41.417332] Pid: 3487, comm: khelper Tainted: G        W  2.6.30-rc1 #1
> > [   41.417332] Call Trace:
> > 
> > the system was doing
> > 
> > [   10.555521] kjournald starting.  Commit interval 5 seconds
> > [   10.556727] EXT3 FS on sdb1, internal journal
> > [   10.556727] EXT3-fs: recovery complete.
> > [   10.557585] EXT3-fs: mounted filesystem with writeback data mode.
> > /dev/sdb1 on /usr/src/all type ext3 (rw,noatime,nodiratime)
> > Detecting hardware: agpgart pcnet32 piix BusLogic ide_scsi
> > Skipping unavailable/built-in agpgart module.
> > pcnet32 disabled in configuration.
> > Skipping unavailable/built-in piix module.
> > Skipping unavailable/built-in BusLogic module.
> > Skipping unavailable/built-in ide_scsi module.
> > Running 0dns-down to make sure resolv.conf is ok...done.
> > Setting up networking...done.
> > Starting hotplug subsystem:
> >    pci     
> >      ignoring pci display device 00:0f.0
> > [   16.727603] ------------[ cut here ]------------
> > [   16.729910] WARNING: at security/security.c:217 security_vm_enough_memory+0xa0/0xb0()
> > 
> > > Though I too find it hard to believe that there were enough to chew up
> > > two minutes.  Maybe the list got corrupted so that it has a loop?
> > 
> > I powered off the machine after two minutes, for I thought the loop
> > was infinite.
> 
> Is this reproducible?  If so, any chance you could try bisecting?

If that's execve() hang, we probably have something->fs->lock stuck.
I don't see any likely candidates, but...

I'd really love to see results of repeated alt-sysrq-p/alt-sysrq-l, just
to see where was it actually spinning.