From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: "Rafael J. Wysocki" To: "Moore, Robert" Cc: Toshi Kani , ACPI Devel Maling List , LKML , Bjorn Helgaas , Jiang Liu , Yinghai Lu , Yasuaki Ishimatsu , Myron Stowe , "linux-pci@vger.kernel.org" Subject: Re: [Update][PATCH] ACPI / hotplug: Fix concurrency issues and memory leaks Date: Thu, 14 Feb 2013 13:03:57 +0100 Message-ID: <7010893.9OBeMt5Fzh@vostro.rjw.lan> In-Reply-To: <94F2FBAB4432B54E8AACC7DFDE6C92E368CB39A9@ORSMSX101.amr.corp.intel.com> References: <1837481.7dT8hTZ4MT@vostro.rjw.lan> <5284026.QPQbFciqVT@vostro.rjw.lan> <94F2FBAB4432B54E8AACC7DFDE6C92E368CB39A9@ORSMSX101.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thursday, February 14, 2013 02:31:22 AM Moore, Robert wrote: > > > > 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. OK, thanks! To me this means that we cannot assume a handle to stay valid between a notify handler and acpi_bus_hot_remove_device() run from a workqueue. Is there a mechanism in ACPICA to ensure that a handle won't become stale while a notify handler is running for it or is the OS responsible for ensuring that _EJ0 won't be run in parallel with notify handlers for device objects being ejected? Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.