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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 530E6C2D0C0 for ; Mon, 23 Dec 2019 14:31:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26A1220709 for ; Mon, 23 Dec 2019 14:31:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="HzWceXyE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727377AbfLWObi (ORCPT ); Mon, 23 Dec 2019 09:31:38 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:18097 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726943AbfLWObK (ORCPT ); Mon, 23 Dec 2019 09:31:10 -0500 Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47hMGb4QXVz9txjy; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=HzWceXyE; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id bkTv1TgFVniR; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 47hMGb3Gynz9txjx; Mon, 23 Dec 2019 15:31:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1577111463; bh=N2ZgUlBGtsvYJmL4aNIvn4kelyr3xUIlcSwbXOh8dAY=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=HzWceXyEVD1Emm0wwEOE1bCdfm4qtJn+RLfuJ+8Hl/RwcdV35a4DNiyknWPUyNLZq wVAMMpO7O4TDPh8O30kOtwmkeCpiX9AOkoMz5d8KvvzSAP/UyJu/lPQ2RvdFwZHmwj 97Amm7bJkkQbo4p6/X7Ca0N8qAiBNpv9MLgC0LWY= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8E2F98B7AB; Mon, 23 Dec 2019 15:31:08 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id LhG5tUkjJ7iO; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: from po16098vm.idsi0.si.c-s.fr (po15451.idsi0.si.c-s.fr [172.25.230.100]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 67BCF8B7A1; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: by po16098vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 71E13637D4; Mon, 23 Dec 2019 14:31:08 +0000 (UTC) Message-Id: In-Reply-To: References: From: Christophe Leroy Subject: [RFC PATCH v2 07/10] lib: vdso: don't use READ_ONCE() in __c_kernel_time() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, x86@kernel.org Date: Mon, 23 Dec 2019 14:31:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org READ_ONCE() forces the read of the 64 bit value of vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec allthough only the lower part is needed. This results in a suboptimal code: 00000af4 <__c_kernel_time>: af4: 2c 03 00 00 cmpwi r3,0 af8: 81 44 00 20 lwz r10,32(r4) afc: 81 64 00 24 lwz r11,36(r4) b00: 41 82 00 08 beq b08 <__c_kernel_time+0x14> b04: 91 63 00 00 stw r11,0(r3) b08: 7d 63 5b 78 mr r3,r11 b0c: 4e 80 00 20 blr By removing the READ_ONCE(), only the lower part is read from memory, and the code is cleaner: 00000af4 <__c_kernel_time>: af4: 7c 69 1b 79 mr. r9,r3 af8: 80 64 00 24 lwz r3,36(r4) afc: 4d 82 00 20 beqlr b00: 90 69 00 00 stw r3,0(r9) b04: 4e 80 00 20 blr Signed-off-by: Christophe Leroy --- lib/vdso/gettimeofday.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index 17b4cff6e5f0..5a17a9d2e6cd 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -144,7 +144,7 @@ __cvdso_gettimeofday(const struct vdso_data *vd, struct __kernel_old_timeval *tv static __maybe_unused __kernel_old_time_t __cvdso_time(const struct vdso_data *vd, __kernel_old_time_t *time) { - __kernel_old_time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); + __kernel_old_time_t t = vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec; if (time) *time = t; -- 2.13.3 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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 9D8B2C2D0CF for ; Mon, 23 Dec 2019 14:50:25 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 04A16206B7 for ; Mon, 23 Dec 2019 14:50:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="HzWceXyE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 04A16206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47hMhv1D6lzDqM5 for ; Tue, 24 Dec 2019 01:50:23 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=c-s.fr (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@c-s.fr; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=c-s.fr header.i=@c-s.fr header.b="HzWceXyE"; dkim-atps=neutral Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47hMGm4wr8zDqKb for ; Tue, 24 Dec 2019 01:31:12 +1100 (AEDT) Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47hMGb4QXVz9txjy; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=HzWceXyE; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id bkTv1TgFVniR; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 47hMGb3Gynz9txjx; Mon, 23 Dec 2019 15:31:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1577111463; bh=N2ZgUlBGtsvYJmL4aNIvn4kelyr3xUIlcSwbXOh8dAY=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=HzWceXyEVD1Emm0wwEOE1bCdfm4qtJn+RLfuJ+8Hl/RwcdV35a4DNiyknWPUyNLZq wVAMMpO7O4TDPh8O30kOtwmkeCpiX9AOkoMz5d8KvvzSAP/UyJu/lPQ2RvdFwZHmwj 97Amm7bJkkQbo4p6/X7Ca0N8qAiBNpv9MLgC0LWY= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8E2F98B7AB; Mon, 23 Dec 2019 15:31:08 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id LhG5tUkjJ7iO; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: from po16098vm.idsi0.si.c-s.fr (po15451.idsi0.si.c-s.fr [172.25.230.100]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 67BCF8B7A1; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: by po16098vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 71E13637D4; Mon, 23 Dec 2019 14:31:08 +0000 (UTC) Message-Id: In-Reply-To: References: From: Christophe Leroy Subject: [RFC PATCH v2 07/10] lib: vdso: don't use READ_ONCE() in __c_kernel_time() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org Date: Mon, 23 Dec 2019 14:31:08 +0000 (UTC) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" READ_ONCE() forces the read of the 64 bit value of vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec allthough only the lower part is needed. This results in a suboptimal code: 00000af4 <__c_kernel_time>: af4: 2c 03 00 00 cmpwi r3,0 af8: 81 44 00 20 lwz r10,32(r4) afc: 81 64 00 24 lwz r11,36(r4) b00: 41 82 00 08 beq b08 <__c_kernel_time+0x14> b04: 91 63 00 00 stw r11,0(r3) b08: 7d 63 5b 78 mr r3,r11 b0c: 4e 80 00 20 blr By removing the READ_ONCE(), only the lower part is read from memory, and the code is cleaner: 00000af4 <__c_kernel_time>: af4: 7c 69 1b 79 mr. r9,r3 af8: 80 64 00 24 lwz r3,36(r4) afc: 4d 82 00 20 beqlr b00: 90 69 00 00 stw r3,0(r9) b04: 4e 80 00 20 blr Signed-off-by: Christophe Leroy --- lib/vdso/gettimeofday.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index 17b4cff6e5f0..5a17a9d2e6cd 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -144,7 +144,7 @@ __cvdso_gettimeofday(const struct vdso_data *vd, struct __kernel_old_timeval *tv static __maybe_unused __kernel_old_time_t __cvdso_time(const struct vdso_data *vd, __kernel_old_time_t *time) { - __kernel_old_time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); + __kernel_old_time_t t = vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec; if (time) *time = t; -- 2.13.3 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 3DE97C2D0C0 for ; Mon, 23 Dec 2019 14:33:08 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1121520715 for ; Mon, 23 Dec 2019 14:33:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oLUIaMdW"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="HzWceXyE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1121520715 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date:To:Subject: From:References:In-Reply-To:Message-Id:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=35n/3HtJPkYgqrgDtdjF/4cA0QYRyTsswvxl6u67bt8=; b=oLUIaMdWXyIRoCUeWozGPz0wN/ wtv6IZbRKJb3a6ILTCk2IlR8GK15vAIUNpJQkDBflZ9v1S/D+OwTEpR623YH9npSwdELZuBzI96jT 49PFGw93/EF+I3koLQdODAzJN1YnHc1mh6XY1VrurZNV5B7rvKpmVI0jRKaRNFKiu6G+cjwdNbQvM TrqoNRh0+mk+mD3UvwO9NjZOGxDQWncUJP1RdkSuG6U+0seNTHShAXhSHEqM+pmF0cgIl1zZhM2SW lvJu7dcXp7RrSyO69NukmBGK/0b2DzJ/5fOD2WXXMjzZ5rH98JWQkaqfWdV5uPT/YxbmleAvmM4H0 32kxHrQg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ijOld-0002Xq-MJ; Mon, 23 Dec 2019 14:33:05 +0000 Received: from pegase1.c-s.fr ([93.17.236.30]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ijOjr-0000n5-2i for linux-arm-kernel@lists.infradead.org; Mon, 23 Dec 2019 14:31:17 +0000 Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47hMGb4QXVz9txjy; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=HzWceXyE; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id bkTv1TgFVniR; Mon, 23 Dec 2019 15:31:03 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 47hMGb3Gynz9txjx; Mon, 23 Dec 2019 15:31:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1577111463; bh=N2ZgUlBGtsvYJmL4aNIvn4kelyr3xUIlcSwbXOh8dAY=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=HzWceXyEVD1Emm0wwEOE1bCdfm4qtJn+RLfuJ+8Hl/RwcdV35a4DNiyknWPUyNLZq wVAMMpO7O4TDPh8O30kOtwmkeCpiX9AOkoMz5d8KvvzSAP/UyJu/lPQ2RvdFwZHmwj 97Amm7bJkkQbo4p6/X7Ca0N8qAiBNpv9MLgC0LWY= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8E2F98B7AB; Mon, 23 Dec 2019 15:31:08 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id LhG5tUkjJ7iO; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: from po16098vm.idsi0.si.c-s.fr (po15451.idsi0.si.c-s.fr [172.25.230.100]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 67BCF8B7A1; Mon, 23 Dec 2019 15:31:08 +0100 (CET) Received: by po16098vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 71E13637D4; Mon, 23 Dec 2019 14:31:08 +0000 (UTC) Message-Id: In-Reply-To: References: From: Christophe Leroy Subject: [RFC PATCH v2 07/10] lib: vdso: don't use READ_ONCE() in __c_kernel_time() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org Date: Mon, 23 Dec 2019 14:31:08 +0000 (UTC) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191223_063115_454485_484B94A8 X-CRM114-Status: GOOD ( 10.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org READ_ONCE() forces the read of the 64 bit value of vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec allthough only the lower part is needed. This results in a suboptimal code: 00000af4 <__c_kernel_time>: af4: 2c 03 00 00 cmpwi r3,0 af8: 81 44 00 20 lwz r10,32(r4) afc: 81 64 00 24 lwz r11,36(r4) b00: 41 82 00 08 beq b08 <__c_kernel_time+0x14> b04: 91 63 00 00 stw r11,0(r3) b08: 7d 63 5b 78 mr r3,r11 b0c: 4e 80 00 20 blr By removing the READ_ONCE(), only the lower part is read from memory, and the code is cleaner: 00000af4 <__c_kernel_time>: af4: 7c 69 1b 79 mr. r9,r3 af8: 80 64 00 24 lwz r3,36(r4) afc: 4d 82 00 20 beqlr b00: 90 69 00 00 stw r3,0(r9) b04: 4e 80 00 20 blr Signed-off-by: Christophe Leroy --- lib/vdso/gettimeofday.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index 17b4cff6e5f0..5a17a9d2e6cd 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -144,7 +144,7 @@ __cvdso_gettimeofday(const struct vdso_data *vd, struct __kernel_old_timeval *tv static __maybe_unused __kernel_old_time_t __cvdso_time(const struct vdso_data *vd, __kernel_old_time_t *time) { - __kernel_old_time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); + __kernel_old_time_t t = vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec; if (time) *time = t; -- 2.13.3 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel