Re: EIP is at device_shutdown+0x32/0x60

[Mark Lord]

Greg KH wrote:
> On Thu, Nov 15, 2007 at 12:07:48PM -0500, Mark Lord wrote:
..
> > Greg, I don't know if this is relevant or not,
> > but x86 has bugs in the halt/reboot code for SMP.
> >
> > Specifically, in native_smp_send_stop() the code now uses
> > spin_trylock() to "lock" the shared call buffers,
> > but then ignores the result.
> >
> > This means that multiple CPUs can/will clobber each other
> > in that code.
> >
> > The second bug, is that this code does not wait for the
> > target CPUs to actually stop before it continues.
> >
> > This was the real cause of the failure-to-poweroff problems
> > I was having with 2.6.23, which we fixed by using CPU hotplug
> > to disable_nonboot_cpus() before the above code ever got run.
>
> I have noticed that the shutdown path is quite weird, shutting down
> sysdev devices differently depending on the type of shutdown, which is
> probably not good.
>
> But what change are you talking about for the poweroff problem?  I have
> a _lot_ of people reporting that 2.6.22 is not powering off for them and
> I can't seem to figure it out.  Do you have a changeset for something
> that went in to fix this issue?
..

Well, the real bugs that cause the problem are described by me above.
I don't have a fix for those, but the workaround is in 2.6.23
under git 4047727e5ae33f9b8d2b7766d1994ea6e5ec2991 Fix SMP poweroff hangs.

With that workaround, there's no more hanging on halt,
though there could still be a hang on reboot.

A problem with that workaround is that it has no effect unless
the CPU hotplug code is configured (CONFIG_PM_SLEEP_SMP and pals).

Cheers
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