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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 E5E5DC5CFE7 for ; Wed, 11 Jul 2018 11:06:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9205220B6F for ; Wed, 11 Jul 2018 11:06:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="umAubXu7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9205220B6F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.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 S1732543AbeGKLKn (ORCPT ); Wed, 11 Jul 2018 07:10:43 -0400 Received: from mail-pl0-f66.google.com ([209.85.160.66]:41740 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726641AbeGKLKn (ORCPT ); Wed, 11 Jul 2018 07:10:43 -0400 Received: by mail-pl0-f66.google.com with SMTP id w8-v6so9020257ply.8 for ; Wed, 11 Jul 2018 04:06:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=Oaa0Ov0L/ZOvGS6M06Oh93oXejBQk3s1MXECgTWSd64=; b=umAubXu7+7XELtC7012+5jqa7JyFASIynVxhQUMwWyYywhFhurUB/m/5iUdkBVM1iQ U0tz8D0bGU1Odyj19ARMB+LiZ7hnbxLWzv4KC7vStAxUIlX6p3xmSrWmKvGmeVzq+7DV 6oaWe2dyqtRAk3njrY9PbRQteLySbl/dTH3FSqKz/PFXCB39IJAFCUyH17ulSbY857MB S78AIx/z05g2Lpp2dOvd32PdopzqW0831KZsZ7gv5oYVYTb6U6ZQqdlzydVAI0Esvg+4 ZY11u1qSU+6wq5FZtk+Z7bZmPO8/m0e4NUHyNZOuM2ae2GP7x8ANraFk2JkSwObdsJzR zBpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=Oaa0Ov0L/ZOvGS6M06Oh93oXejBQk3s1MXECgTWSd64=; b=JTKuZqSvnYnpm5gAteo/wkJqIS3fIR7zvQv/jM6V6r/6wfY4J/AO51YIAvcMEEGeDh kdXlqcqYaJ+5RMaWBdejJjKnqaUUe6jg9reJFMqZt1VPUtgEzZvQLp7gqmcl4OG0cWPl uAcS4ZS51Cg3odwNolvq7XkPZMcP0rCQZDTDfX7VkKJFZzuP3KxfLJxHgyPcZoVooytF nNE4DoyQb6FgaQWRElXVG0En+edy51M3m7uNxckthAA+P/5Zit3lYTHFexPuPojHmUk8 f0sVms0ezKwo8cR0+Ui+Tj2o+Ns9zIuJuFAi7HPWSdqO+3Z7b8oeoSxaV3aNuYJWcAla xnOA== X-Gm-Message-State: APt69E21hnYFLWzl7U4I4OD0IZ2jWrt1Cxnk3EPI4WH1A09FgHuRy05j VKHLasKJsSKM5yG8dx6SgUiypCVz X-Google-Smtp-Source: AAOMgpeOJrKYA6aEA5jBgvNekcY0fz3enED+tRP7Qi1KLo25pY5ZbiZkBRo6K/mzOUGCasQraehLRA== X-Received: by 2002:a17:902:42a3:: with SMTP id h32-v6mr27983134pld.72.1531307216143; Wed, 11 Jul 2018 04:06:56 -0700 (PDT) Received: from bj03003pcul8.spreadtrum.com ([117.18.48.82]) by smtp.gmail.com with ESMTPSA id l25-v6sm3767701pff.8.2018.07.11.04.06.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 11 Jul 2018 04:06:55 -0700 (PDT) From: "Yandong.Zhao" To: Dave.Martin@arm.com Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org, will.deacon@arm.com, catalin.marinas@arm.com, zhaoyd@thundersoft.com, zhaoxb@thundersoft.com, fanlc0801@thundersoft.com, Yandong Zhao Subject: [PATCH] arm64: neon: Fix function may_use_simd() return error status Date: Wed, 11 Jul 2018 19:06:28 +0800 Message-Id: <1531307188-12032-1-git-send-email-yandong77520@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(-) diff --git a/arch/arm64/include/asm/simd.h b/arch/arm64/include/asm/simd.h index fa8b3fe..784a8c2 100644 --- a/arch/arm64/include/asm/simd.h +++ b/arch/arm64/include/asm/simd.h @@ -29,7 +29,8 @@ static __must_check inline bool may_use_simd(void) { /* - * The raw_cpu_read() is racy if called with preemption enabled. + * The this_cpu_read() is racy if called with preemption enabled, + * since the task may subsequently migrate to another CPU. * This is not a bug: kernel_neon_busy is only set when * preemption is disabled, so we cannot migrate to another CPU * while it is set, nor can we migrate to a CPU where it is set. @@ -42,7 +43,7 @@ static __must_check inline bool may_use_simd(void) * false. */ return !in_irq() && !irqs_disabled() && !in_nmi() && - !raw_cpu_read(kernel_neon_busy); + !this_cpu_read(kernel_neon_busy); } #else /* ! CONFIG_KERNEL_MODE_NEON */ -- 1.9.1