linux-kernel - RE: [Update][PATCH] ACPI / hotplug: Fix concurrency issues and memory leaks

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Date:	Thu, 14 Feb 2013 02:31:22 +0000
From:	"Moore, Robert" <robert.moore@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>, Toshi Kani <toshi.kani@...com>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <liuj97@...il.com>, Yinghai Lu <yinghai@...nel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Myron Stowe <mstowe@...hat.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: RE: [Update][PATCH] ACPI / hotplug: Fix concurrency issues and
 memory leaks

> > > I thought about that, but actually there's no guarantee that the
> > > handle will be valid after _EJ0 as far as I can say.  So the race
> > > condition is going to be there anyway and using struct acpi_device
> > > just makes it easier to avoid it.
> >
> > In theory, yes, a stale handle could be a problem, if _EJ0 performs
> > unload table and if ACPICA frees up its internal data structure
> > pointed by the handle as a result.  But we should not see such issue
> > now since we do not support dynamic ACPI namespace yet.
> 
> I'm waiting for information from Bob about that.  If we can assume ACPI
> handles to be always valid, that will simplify things quite a bit.

If a table is unloaded, all the namespace nodes for that table are removed from the namespace, and thus any ACPI_HANDLE pointers go stale and invalid.

Bob