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Fri, 30 Mar 2018 15:58:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1522425500; bh=QZbzmzB+wngm0aJQ8lOWK+iJYyejFtpxDn5Ruh/0EeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S4HBD+wwBseNc77kgjhxfzDkWNMQGHu6jn/y+og0IgVOaffXxvdd67PdsI019Lcib trDcFGLhhuab3P5pne6bQKNXIRzP4g1Gg5cmBgFdeSl3sP8byMAQ48bhMoV3hTh1ok mmRL9Omtdcjvc0F9apBU9lZ9Ea2prMF8Ngkdkm00= 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180330_085830_344041_160F025C X-CRM114-Status: GOOD ( 11.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sinan Kaya , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP 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 */