From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57EABC433E3 for ; Sun, 16 Aug 2020 21:05:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 222EA204FD for ; Sun, 16 Aug 2020 21:05:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="qKGBnTIC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728572AbgHPVF0 (ORCPT ); Sun, 16 Aug 2020 17:05:26 -0400 Received: from mail.efficios.com ([167.114.26.124]:35876 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726425AbgHPVFX (ORCPT ); Sun, 16 Aug 2020 17:05:23 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id DAA9B2CD070; Sun, 16 Aug 2020 17:05:22 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id mXJFxJKv4xmv; Sun, 16 Aug 2020 17:05:22 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 834D12CD2DA; Sun, 16 Aug 2020 17:05:22 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 834D12CD2DA DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1597611922; bh=UJk0iDK6i/D5vytzbwL67FL+4Gn317iKgz3d3kMyssI=; h=Date:From:To:Message-ID:MIME-Version; b=qKGBnTICgxQ2itmJABPx7EhVNoBmOY04vtFZoexbu0cirnpu3hoA+YGgRwUFfBlyQ /jjfofteztn/IqOZWdCCCVVWqznZOocCy966A7Y+YhbIy/DE0omCikrMjx2h2XVx12 gn2HWEOctGt4nF8+8FI583vErmPiIkKQ4WCJGkgbkjntQGIs5Rr4dCh1D8zygoo642 V3SUJaKScG1TIY4DANiVYWrlqzksHXdxiabva451mwVal9qUqfLxPc1f8LE8g2eDRH e3bEOiD1kASIQyACLqhNUigPPTXe/qB6HVhBDOmlR8XDB0ipXQ66+pOl8wod5gtHoc EfAvfzA7NJ9qw== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 9hMwMGCXnLHo; Sun, 16 Aug 2020 17:05:22 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 527F52CD179; Sun, 16 Aug 2020 17:05:22 -0400 (EDT) Date: Sun, 16 Aug 2020 17:05:22 -0400 (EDT) From: Mathieu Desnoyers To: Hillf Danton Cc: Peter Zijlstra , linux-kernel , Will Deacon , paulmck , Andy Lutomirski , Andrew Morton , Alan Stern , Nicholas Piggin Message-ID: <833020242.9878.1597611922236.JavaMail.zimbra@efficios.com> In-Reply-To: <20200816070932.10752-1-hdanton@sina.com> References: <20200814164358.4783-1-mathieu.desnoyers@efficios.com> <20200816070932.10752-1-hdanton@sina.com> Subject: Re: [RFC PATCH 2/3] sched: membarrier: cover kthread_use_mm (v2) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_3959 (ZimbraWebClient - FF79 (Linux)/8.8.15_GA_3953) Thread-Topic: sched: membarrier: cover kthread_use_mm (v2) Thread-Index: rImpRoT9yXbFw6ZT6L56QCI7o+oPnQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Aug 16, 2020, at 3:09 AM, Hillf Danton hdanton@sina.com wrote: > On Fri, 14 Aug 2020 12:43:57 -0400 Mathieu Desnoyers wrote: >> >> Given that no prior kthread use this guarantee and that it only affects >> kthreads, adding this guarantee does not affect user-space ABI. > > Can you expand a bit on why kthreads like ksoftirqd have to ack the > IPIs from Dave who's not CAP_SYS_ADMIN. Do ksoftirqd kthreads ever use kthread_use_mm() to access user processes' memory ? If not, then they won't be disturbed by any IPI. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com