Re: [PATCH] ACPI / scan: Make it clear that acpi_bus_trim() cannotfail

From: Vasilis Liaskovitis
Date: Mon Feb 18 2013 - 09:53:52 EST

On Mon, Feb 18, 2013 at 02:17:02PM +0100, Rafael J. Wysocki wrote:
> On Monday, February 18, 2013 01:25:49 PM Vasilis Liaskovitis wrote:
> > Hi,
> >
> > On Thu, Jan 24, 2013 at 11:56:50PM +0100, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > >
> > > Since acpi_bus_trim() cannot fail, change its definition to a void
> > > function, so that its callers don't check the return value in vain
> > > and update the callers.
> >
> > I have missed a few patchsets/discussions in the last month and wanted to
> > ask a question related to this: Does the new always-succeed 2-pass
> > trim_device design guarantee safe memory hot-remove operations?
> I doesn't by itself. Nor it really can, because the .remove() callbacks of
> device drivers are not allowed to fail.


> > Afaict if memory offline fails now, the device is ejected (_EJ0) anyways
> > causing a panic. Tested in a VM with linux-next-20130207 and
> > linux-next-20130218 by doing an SCI-eject request on a hot-plugged dimm.
> >
> > Are there more patches in development for safe memory hot-remove?
> Yes, there are. I sent a patch series yesterday introducing some safety
> measures (you can disable memory hotplug from user space or disable
> automatic ejection). There's more to come still.
> The plan is to introduce offline/online operations for memory modules (in
> analogy with CPU core online/offline) that can be started by user space and
> memory eject will only be possible after offline (i.e. when the memory module
> is known to be not in use).

ok, thanks for the info. I 'll test these and the follow ups.

thanks again,

- Vasilis
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