From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Starikovskiy Subject: Re: Bug: linux/acpi may execute notify handler that has been removed Date: Thu, 27 Sep 2007 10:24:45 +0400 Message-ID: <46FB4CAD.7050201@suse.de> References: <1190863833.26892.63.camel@acpi-hp.sh.intel.com> <1190868847.22470.0.camel@sli10-conroe.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from charybdis-ext.suse.de ([195.135.221.2]:46488 "EHLO emea5-mh.id5.novell.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753067AbXI0GZN (ORCPT ); Thu, 27 Sep 2007 02:25:13 -0400 In-Reply-To: <1190868847.22470.0.camel@sli10-conroe.sh.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Shaohua Li Cc: Zhang Rui , linux-acpi@vger.kernel.org, "Moore, Robert" Shaohua Li wrote: > On Thu, 2007-09-27 at 11:30 +0800, Zhang Rui wrote: >> Hi, all, >> >> I found a bug that linux/acpi may execute notify handler that >> has been removed. >> >> When a system notify(0~0x7f) is received, linux/acpi will >> first invoke the generic system notify handler (acpi_bus_notify) >> and then invoke the per-device notify handler if present. >> >> In my case, I add some code in acpi_bus_notify for battery >> hotplug support, so that the generic system notify handler will >> remove the battery device, including the per-device notify handler >> acpi_battery_notify() when receiving notification >> ACPI_NOTIFY_EJECT_REQUEST. >> But linux/acpi invokes the per-device notify handler soon and >> this breaks the system. >> >> Further more, device hot-removal is not the only case to encounter >> this bug. For example, linux/acpi receives a notification and adds it >> in the workqueue, and then the driver(notify handler) is removed >> before kacpid_notify invoke it... > For the non-hotplug case, adding a flush work queue just after notify > handler is removed should be ok. I think, the real problem with ACPI hotplug is that we know which devices might appear -- they are all enumerated in DSDT, but we don't add them until they appear. If we do .add for all devices in DSDT, and then just .start/.stop them as they appear/disappear, we will have to do much less work, and avoid a problem described above... Regards, Alex.