Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Fri, Oct 25, 2013 at 10:02:22AM +0100, Linus Torvalds wrote:
> Adding more people, so quoting the whole email for them.
> 
> We definitely have some module unload issues. Guys, try the following
> a few times to unload modules:
> 
>     lsmod | grep ' 0 '| cut -d' ' -f1 | xargs sudo rmmod
> 
> (a few times because unloading one module will then potentially make
> other modules unloadable).

Isn't it still the user's responsibility to ensure that a module will
no longer being used before rmmod-ing it?  Or were all those race
conditions fixed?

							Thanx, Paul

> On my machine, I can trigger this, for example:
> 
>   ------------[ cut here ]------------
>   WARNING: CPU: 0 PID: 3217 at fs/sysfs/file.c:498 sysfs_attr_ns+0x91/0xa0()
>   sysfs: kobject (null) without dirent
>   Modules linked in: fuse nf_conntrack_broadcast ipt_MASQUERADE ip6t_REJECT xt_$
>   CPU: 0 PID: 3217 Comm: rmmod Not tainted 3.12.0-rc6-00284-ge6036c0b8896 #19
>   Hardware name: Sony Corporation SVP11213CXB/VAIO, BIOS R0270V7 05/17/2013
>    0000000000000009 ffff8800aca35df8 ffffffff8160aab5 ffff8800aca35e40
>    ffff8800aca35e30 ffffffff810514b8 ffffffffa013f080 ffff8801194a6040
>    0000000000000800 0000000000000000 0000000000c5b3e0 ffff8800aca35e90
>   Call Trace:
>    [<ffffffff8160aab5>] dump_stack+0x45/0x56
>    [<ffffffff810514b8>] warn_slowpath_common+0x78/0xa0
>    [<ffffffff81051527>] warn_slowpath_fmt+0x47/0x50
>    [<ffffffff810b5960>] ? module_refcount+0xb0/0xb0
>    [<ffffffff811e5c61>] sysfs_attr_ns+0x91/0xa0
>    [<ffffffff811e5d2a>] sysfs_remove_file+0x1a/0x50
>    [<ffffffff814c88a3>] cpufreq_sysfs_remove_file+0x13/0x30
>    [<ffffffffa013d350>] acpi_cpufreq_exit+0x2e/0xcde [acpi_cpufreq]
>    [<ffffffff810b7d1d>] SyS_delete_module+0x15d/0x2c0
>    [<ffffffff81002929>] ? do_notify_resume+0x59/0x90
>    [<ffffffff81618f62>] system_call_fastpath+0x16/0x1b
>   ---[ end trace f887112caaa5c4ab ]---
> 
> so at least we have a cpufreq/sysfs interaction bug. There may be others.
> 
> This particular cpufreq issue may be triggered by the fact that
> acpi-cpufreq isn't actually in use (pstate is). Or it might be some
> generic cpufreq/sysfs bug. Rafael, Greg, ideas?
> 
> I don't see that this particular one would be the one that causes the
> timer issues, but it's an example of the fact that module unload tends
> to be special and not necessarily well tested.
> 
>                    Linus
> 
> On Fri, Oct 25, 2013 at 9:38 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > Hmm.. I just got a run_timer_softirq oops on my own laptop, slightly
> > different. That was not during shutdown, although there was a "yum
> > upgrade" finishing when that happened, so it's quite likely that there
> > was a service shutdown (and then restart).
> >
> > I think it's related. But my oops has almost no information: the IP
> > that was jumped to was bogus, and the callchain is just CPU idle
> > followed by the softirq -> run_timers_softirq handling, so there's no
> > real way to see *what* triggered it.
> >
> > The bad rip was ffffffffa051e250, which is not a valid code address.
> > It *might* be a module address, though. So this might be triggered by
> > rmmod on some module that doesn't remove all its timers...
> >
> > Ideas?
> >
> >                  Linus
>