From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752188AbeC3P6b (ORCPT ); Fri, 30 Mar 2018 11:58:31 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:57464 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751264AbeC3P6V (ORCPT ); Fri, 30 Mar 2018 11:58:21 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 9FEE360817 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=okaya@codeaurora.org From: Sinan Kaya To: arnd@arndb.de, timur@codeaurora.org, sulrich@codeaurora.org Cc: linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sinan Kaya , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] io: prevent compiler reordering on the default readX() implementation Date: Fri, 30 Mar 2018 11:58:13 -0400 Message-Id: <1522425494-2916-2-git-send-email-okaya@codeaurora.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1522425494-2916-1-git-send-email-okaya@codeaurora.org> References: <1522425494-2916-1-git-send-email-okaya@codeaurora.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The default implementation of mapping readX() to __raw_readX() is wrong. readX() has stronger ordering semantics. Compiler is allowed to reorder __raw_readX(). In the abscence of a read barrier or when using a strongly ordered architecture, readX() should at least have a compiler barrier in it to prevent commpiler from clobbering the execution order. Signed-off-by: Sinan Kaya --- include/asm-generic/io.h | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h index e8c2078..2554f15 100644 --- a/include/asm-generic/io.h +++ b/include/asm-generic/io.h @@ -110,7 +110,12 @@ static inline void __raw_writeq(u64 value, volatile void __iomem *addr) #define readb readb static inline u8 readb(const volatile void __iomem *addr) { - return __raw_readb(addr); + u8 val; + + val = __raw_readb(addr); + barrier(); + + return val; } #endif @@ -118,7 +123,12 @@ static inline u8 readb(const volatile void __iomem *addr) #define readw readw static inline u16 readw(const volatile void __iomem *addr) { - return __le16_to_cpu(__raw_readw(addr)); + u16 val; + + val = __le16_to_cpu(__raw_readw(addr)); + barrier(); + + return val; } #endif @@ -126,7 +136,12 @@ static inline u16 readw(const volatile void __iomem *addr) #define readl readl static inline u32 readl(const volatile void __iomem *addr) { - return __le32_to_cpu(__raw_readl(addr)); + u32 val; + + val = __le32_to_cpu(__raw_readl(addr)); + barrier(); + + return val; } #endif @@ -135,7 +150,12 @@ static inline u32 readl(const volatile void __iomem *addr) #define readq readq static inline u64 readq(const volatile void __iomem *addr) { - return __le64_to_cpu(__raw_readq(addr)); + u64 val; + + val = __le64_to_cpu(__raw_readq(addr)); + barrier(); + + return val; } #endif #endif /* CONFIG_64BIT */ -- 2.7.4