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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 1521BC5CFEB for ; Wed, 11 Jul 2018 12:58:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D03A52084A for ; Wed, 11 Jul 2018 12:58:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D03A52084A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387437AbeGKNCn (ORCPT ); Wed, 11 Jul 2018 09:02:43 -0400 Received: from foss.arm.com ([217.140.101.70]:35220 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387405AbeGKNCn (ORCPT ); Wed, 11 Jul 2018 09:02:43 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 90C497A9; Wed, 11 Jul 2018 05:58:29 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E99443F5AD; Wed, 11 Jul 2018 05:58:27 -0700 (PDT) Date: Wed, 11 Jul 2018 13:58:25 +0100 From: Dave Martin To: Will Deacon Cc: "Yandong.Zhao" , zhaoxb@thundersoft.com, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, zhaoyd@thundersoft.com, linux-arm-kernel@lists.infradead.org, fanlc0801@thundersoft.com Subject: Re: [PATCH] arm64: neon: Fix function may_use_simd() return error status Message-ID: <20180711125825.GM9486@e103592.cambridge.arm.com> References: <1531307188-12032-1-git-send-email-yandong77520@gmail.com> <20180711120519.GC15725@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180711120519.GC15725@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 11, 2018 at 01:05:19PM +0100, Will Deacon wrote: > On Wed, Jul 11, 2018 at 07:06:28PM +0800, Yandong.Zhao wrote: > > From: Yandong Zhao > > > > It does not matter if the caller of may_use_simd() migrates to > > another cpu after the call, but it is still important that the > > kernel_neon_busy percpu instance that is read matches the cpu the > > task is running on at the time of the read. > > > > This means that raw_cpu_read() is not sufficient. kernel_neon_busy > > may appear true if the caller migrates during the execution of > > raw_cpu_read() and the next task to be scheduled in on the initial > > cpu calls kernel_neon_begin(). > > > > This patch replaces raw_cpu_read() with this_cpu_read() to protect > > against this race. > > > > Fixes: cb84d11e1625 ("arm64: neon: Remove support for nested or hardirq kernel-mode NEON") > > Reviewed-by: Dave Martin > > Signed-off-by: Yandong Zhao > > --- > > arch/arm64/include/asm/simd.h | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > Does this need to go to stable? It should, yes, so we should probably add Cc: stable@vger.kernel.org Are you OK to pick that up? Cheers ---Dave