From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx159.postini.com [74.125.245.159]) by kanga.kvack.org (Postfix) with SMTP id E8BA86B0062 for ; Mon, 26 Nov 2012 19:27:26 -0500 (EST) Message-ID: <1353975541.26955.182.camel@misato.fc.hp.com> Subject: Re: [RFC PATCH v3 3/3] acpi_memhotplug: Allow eject to proceed on rebind scenario From: Toshi Kani Date: Mon, 26 Nov 2012 17:19:01 -0700 In-Reply-To: <50B3323E.7020907@cn.fujitsu.com> References: <1353693037-21704-1-git-send-email-vasilis.liaskovitis@profitbricks.com> <1353693037-21704-4-git-send-email-vasilis.liaskovitis@profitbricks.com> <50B0F3DF.4000802@gmail.com> <20121126083634.GA4574@dhcp-192-168-178-175.profitbricks.localdomain> <50B3323E.7020907@cn.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Wen Congyang Cc: Vasilis Liaskovitis , Wen Congyang , linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com, rjw@sisk.pl, lenb@kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org > >> Consider the following sequence of operations for a hotplugged memory > >> device: > >> > >> 1. echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind > >> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject > >> > >> If we don't offline/remove the memory, we have no chance to do it in > >> step 2. After > >> step2, the memory is used by the kernel, but we have powered off it. It > >> is very > >> dangerous. > > > > How does power-off happen after unbind? acpi_eject_store checks for existing > > driver before taking any action: > > > > #ifndef FORCE_EJECT > > if (acpi_device->driver == NULL) { > > ret = -ENODEV; > > goto err; > > } > > #endif > > > > FORCE_EJECT is not defined afaict, so the function returns without scheduling > > acpi_bus_hot_remove_device. Is there another code path that calls power-off? > > Consider the following case: > > We hotremove the memory device by SCI and unbind it from the driver at the same time: > > CPUa CPUb > acpi_memory_device_notify() > unbind it from the driver > acpi_bus_hot_remove_device() Can we make acpi_bus_remove() to fail if a given acpi_device is not bound with a driver? If so, can we make the unbind operation to perform unbind only? 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