Re: [PATCH] ACPI: bind workqueues to CPU 0 to avoid SMI corruption

[Shaohua Li <shaohua.li@intel.com>]

On Thu, Jul 30, 2009 at 10:55:54AM +0800, Matthew Garrett wrote:
> On Thu, Jul 30, 2009 at 10:43:00AM +0800, Shaohua Li wrote:
> > On Thu, Jul 30, 2009 at 05:54:25AM +0800, Bjorn Helgaas wrote:
> > > On some machines, a software-initiated SMI causes corruption unless the
> > > SMI runs on CPU 0.  An SMI can be initiated by any AML, but typically it's
> > > done in GPE-related methods that are run via workqueues, so we can avoid
> > > the known corruption cases by binding the workqueues to CPU 0.
> > > 
> > > References:
> > >     http://bugzilla.kernel.org/show_bug.cgi?id=13751
> > >     https://bugs.launchpad.net/bugs/157171
> > >     https://bugs.launchpad.net/bugs/157691
> > Good job! Since any AML code can invoke a SMI, I wonder if all ACPICA should be
> > limited to run on CPU 0?
> 
> If ACPI is a performance bottleneck then we have other problems, so I 
> suspect that we could live with that. We'd probably want to be able to 
> disable it at runtime for the small number of users who have 
> "interesting" performance requirements, but falling on the side of 
> safety over slightly reduced latency under some circumstances seems fair 
> to me. It'd be interesting to see if this helps with any of the other 
> SMI-related hangs we've seeni.
ACPICA isn't designed for performance. If it has performance issue, it should
already have.