Re: [Lhms-devel] Re: [PATCH] ACPI based Memory Hotplug Driver Patch

[Dave Hansen <haveblue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On Fri, 2004-09-10 at 23:08, Hirokazu Takahashi wrote:
> > 'acpi_memory_enable/disable_device()' seem to call generic
> > (not ACPI specific) hotplug functions 'add/remove_memory()' directly.
> > I think the generic hotplug functions should not be called directly
> > inside kernel, but from the userland for two reasons.
> 
> And remove_memory() should be invoked from a process context,
> as it would write-back data on the memory or would wait for
> the memroy becoming freeable. It can't be removed as long as
> there remain references to it.
> 
> It would cause weird problems if the function is called from an ACPI
> handler directly.

I don't think this is true.  It would be a problem if we were calling
sys_write() on the sysfs files from inside of there, but those
interfaces are *there* for firmware to call them.  

In fact, I think we even mention that where they're defined.  As long as
we claim that they might_sleep(), and ACPI isn't holding any locks at
the time, or in interrupt context, where's the problem?  Worst case, we
schedule_work() to have the removal done in a sleepable context.

-- Dave



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