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

[Mark Lord <lkml@rtr.ca>]

Greg KH wrote:
> On Thu, Nov 15, 2007 at 01:29:04PM -0500, Mark Lord wrote:
> > 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).
>
> Hm, that's not going to be a fix for 2.6.22 as we already do a call to
> that function in that call when shutting down, something in the
> 2.6.23-rc series must have changed that logic to make it required again.
..

But remember, it has no effect unless the kernel has suspend/resume
configured in.  Many desktops don't.

And the real unfixed bugs are still there in native_smp_send_stop()
as described above.  You could prod whoever takes care of that code
to fix them.

Cheers
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