From mboxrd@z Thu Jan 1 00:00:00 1970 From: Toshi Kani Subject: Re: [RFC PATCH v2 0/3] acpi: Introduce prepare_remove device operation Date: Fri, 16 Nov 2012 15:45:43 -0700 Message-ID: <1353105943.12509.60.camel@misato.fc.hp.com> References: <1352974970-6643-1-git-send-email-vasilis.liaskovitis@profitbricks.com> <1446291.TgLDtXqY7q@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:41774 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753797Ab2KPWx6 (ORCPT ); Fri, 16 Nov 2012 17:53:58 -0500 In-Reply-To: <1446291.TgLDtXqY7q@vostro.rjw.lan> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: Vasilis Liaskovitis , linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, lenb@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman On Fri, 2012-11-16 at 22:43 +0100, Rafael J. Wysocki wrote: > On Thursday, November 15, 2012 11:22:47 AM Vasilis Liaskovitis wrote: > > As discussed in https://patchwork.kernel.org/patch/1581581/ > > the driver core remove function needs to always succeed. This means we need > > to know that the device can be successfully removed before acpi_bus_trim / > > acpi_bus_hot_remove_device are called. This can cause panics when OSPM-initiated > > eject or driver unbind of memory devices fails e.g with: > > > > echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject > > echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind > > > > since the ACPI core goes ahead and ejects the device regardless of whether the > > the memory is still in use or not. > > So the question is, does the ACPI core have to do that and if so, then why? The problem is that acpi_memory_devcie_remove() can fail. However, device_release_driver() is a void function, so it cannot report its error. Here are function flows for SCI, sysfs eject and unbind. SCI & sysfs eject === acpi_bus_hot_remove_device() acpi_bus_trim() acpi_bus_remove() device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver acpi_evaluate_object(handle, "_EJ0",,) // Eject sysfs unbind === driver_unbind() // Driver Core device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver put_device() bus_put() Yasuaki's approach was to change device_release_driver() to report an error so that acpi_bus_hot_remove_device() can fail without ejecting. Vasilis's approach was to call ACPI driver via a new interface before device_release_driver(), but still requires to change driver_unbind(). It looks to me that some changes to driver core is needed... Thanks, -Toshi From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx143.postini.com [74.125.245.143]) by kanga.kvack.org (Postfix) with SMTP id C27CC6B0068 for ; Fri, 16 Nov 2012 17:53:58 -0500 (EST) Message-ID: <1353105943.12509.60.camel@misato.fc.hp.com> Subject: Re: [RFC PATCH v2 0/3] acpi: Introduce prepare_remove device operation From: Toshi Kani Date: Fri, 16 Nov 2012 15:45:43 -0700 In-Reply-To: <1446291.TgLDtXqY7q@vostro.rjw.lan> References: <1352974970-6643-1-git-send-email-vasilis.liaskovitis@profitbricks.com> <1446291.TgLDtXqY7q@vostro.rjw.lan> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Rafael J. Wysocki" Cc: Vasilis Liaskovitis , linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, lenb@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman On Fri, 2012-11-16 at 22:43 +0100, Rafael J. Wysocki wrote: > On Thursday, November 15, 2012 11:22:47 AM Vasilis Liaskovitis wrote: > > As discussed in https://patchwork.kernel.org/patch/1581581/ > > the driver core remove function needs to always succeed. This means we need > > to know that the device can be successfully removed before acpi_bus_trim / > > acpi_bus_hot_remove_device are called. This can cause panics when OSPM-initiated > > eject or driver unbind of memory devices fails e.g with: > > > > echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject > > echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind > > > > since the ACPI core goes ahead and ejects the device regardless of whether the > > the memory is still in use or not. > > So the question is, does the ACPI core have to do that and if so, then why? The problem is that acpi_memory_devcie_remove() can fail. However, device_release_driver() is a void function, so it cannot report its error. Here are function flows for SCI, sysfs eject and unbind. SCI & sysfs eject === acpi_bus_hot_remove_device() acpi_bus_trim() acpi_bus_remove() device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver acpi_evaluate_object(handle, "_EJ0",,) // Eject sysfs unbind === driver_unbind() // Driver Core device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver put_device() bus_put() Yasuaki's approach was to change device_release_driver() to report an error so that acpi_bus_hot_remove_device() can fail without ejecting. Vasilis's approach was to call ACPI driver via a new interface before device_release_driver(), but still requires to change driver_unbind(). It looks to me that some changes to driver core is needed... Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org