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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 23680C43441 for ; Thu, 8 Nov 2018 22:28:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCFA920857 for ; Thu, 8 Nov 2018 22:28:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="bChDUMU8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DCFA920857 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org 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 S1730926AbeKIHjR (ORCPT ); Fri, 9 Nov 2018 02:39:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:58912 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728085AbeKIHjR (ORCPT ); Fri, 9 Nov 2018 02:39:17 -0500 Received: from localhost (unknown [208.72.13.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E9C27208E3; Thu, 8 Nov 2018 22:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541714508; bh=tZxv+KaOyiGHq5qWK+Ccv4oFJku2+/pF55clW50yChk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bChDUMU8iLkZgO4t36IB1sJL38qK8V1NWZHbAFQUesfl4lAuxiCQEJD28+mduC2j3 UN+C/XyeNNj3u+CdSU1NrE2zPJEGTJJmJVeUkVI7wW41dBG3JeidGx7J/yElkKUJ4T hm9UEIbODFAwkn4Z8jyXI8/OT0+U2Ef9tsd8y5Os= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , "Peter Zijlstra (Intel)" , Thomas Gleixner , hpa@zytor.com, eric.dumazet@gmail.com, bp@alien8.de Subject: [PATCH 4.4 113/114] x86/percpu: Fix this_cpu_read() Date: Thu, 8 Nov 2018 13:52:08 -0800 Message-Id: <20181108215111.026443173@linuxfoundation.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181108215059.051093652@linuxfoundation.org> References: <20181108215059.051093652@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit b59167ac7bafd804c91e49ad53c6d33a7394d4c8 upstream. Eric reported that a sequence count loop using this_cpu_read() got optimized out. This is wrong, this_cpu_read() must imply READ_ONCE() because the interface is IRQ-safe, therefore an interrupt can have changed the per-cpu value. Fixes: 7c3576d261ce ("[PATCH] i386: Convert PDA into the percpu section") Reported-by: Eric Dumazet Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Acked-by: Eric Dumazet Cc: hpa@zytor.com Cc: eric.dumazet@gmail.com Cc: bp@alien8.de Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181011104019.748208519@infradead.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/percpu.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -184,22 +184,22 @@ do { \ typeof(var) pfo_ret__; \ switch (sizeof(var)) { \ case 1: \ - asm(op "b "__percpu_arg(1)",%0" \ + asm volatile(op "b "__percpu_arg(1)",%0"\ : "=q" (pfo_ret__) \ : "m" (var)); \ break; \ case 2: \ - asm(op "w "__percpu_arg(1)",%0" \ + asm volatile(op "w "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : "m" (var)); \ break; \ case 4: \ - asm(op "l "__percpu_arg(1)",%0" \ + asm volatile(op "l "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : "m" (var)); \ break; \ case 8: \ - asm(op "q "__percpu_arg(1)",%0" \ + asm volatile(op "q "__percpu_arg(1)",%0"\ : "=r" (pfo_ret__) \ : "m" (var)); \ break; \