Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752031AbdGaIyF (ORCPT ); Mon, 31 Jul 2017 04:54:05 -0400 Received: from mail-wr0-f172.google.com ([209.85.128.172]:32937 "EHLO mail-wr0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752007AbdGaIyE (ORCPT ); Mon, 31 Jul 2017 04:54:04 -0400 Subject: Re: Udpated sys_membarrier() speedup patch, FYI To: Peter Zijlstra Cc: Mathieu Desnoyers , "Paul E. McKenney" , maged michael , Andrew Hunter , gromer , linux-kernel References: <20170727181250.GA20183@linux.vnet.ibm.com> <5c8c6946-ce3a-6183-76a2-027823a9948a@scylladb.com> <20170727194322.GL3730@linux.vnet.ibm.com> <5fe39d32-5fc1-3a59-23fc-9bdb1d90edf9@scylladb.com> <20170727203706.GO3730@linux.vnet.ibm.com> <1035920775.29109.1501189118277.JavaMail.zimbra@efficios.com> <1546253326.29115.1501189344518.JavaMail.zimbra@efficios.com> <20170731083746.mggdh7pcdycjte2c@hirez.programming.kicks-ass.net> From: Avi Kivity Organization: ScyllaDB Message-ID: <3ac1d851-d833-004c-3c3b-b4d804cbca69@scylladb.com> Date: Mon, 31 Jul 2017 11:53:59 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170731083746.mggdh7pcdycjte2c@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 444 Lines: 8 On 07/31/2017 11:37 AM, Peter Zijlstra wrote: > On Mon, Jul 31, 2017 at 09:03:09AM +0300, Avi Kivity wrote: >> I remembered that current->mm does not change when switching to a kernel >> task, but my Kernlish is very rusty, or maybe it has changed. > kernel threads do indeed preserve the mm of the old userspace task, but > we track that in ->active_mm. Their ->mm will be NULL. Gah, I'm so rusty, if I were any rustier I'd be doing bitcoin.