From patchwork Tue Jun 25 16:18:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincenzo Frascino X-Patchwork-Id: 11015959 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0F6996C5 for ; Tue, 25 Jun 2019 16:18:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0081C27F89 for ; Tue, 25 Jun 2019 16:18:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E84A027F93; Tue, 25 Jun 2019 16:18:47 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 864E527F89 for ; Tue, 25 Jun 2019 16:18:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726696AbfFYQSf (ORCPT ); Tue, 25 Jun 2019 12:18:35 -0400 Received: from foss.arm.com ([217.140.110.172]:44760 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726420AbfFYQSf (ORCPT ); Tue, 25 Jun 2019 12:18:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 916D1360; Tue, 25 Jun 2019 09:18:34 -0700 (PDT) Received: from e119884-lin.cambridge.arm.com (e119884-lin.cambridge.arm.com [10.1.196.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F12313F718; Tue, 25 Jun 2019 09:18:31 -0700 (PDT) From: Vincenzo Frascino To: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: catalin.marinas@arm.com, will.deacon@arm.com, arnd@arndb.de, linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com, daniel.lezcano@linaro.org, tglx@linutronix.de, salyzyn@android.com, pcc@google.com, shuah@kernel.org, 0x7f454c46@gmail.com, linux@rasmusvillemoes.dk, huw@codeweavers.com, sthotton@marvell.com, andre.przywara@arm.com Subject: [PATCH 1/3] lib/vdso: Delay mask application in do_hres() Date: Tue, 25 Jun 2019 17:18:02 +0100 Message-Id: <20190625161804.38713-1-vincenzo.frascino@arm.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190624133607.GI29497@fuggles.cambridge.arm.com> References: <20190624133607.GI29497@fuggles.cambridge.arm.com> MIME-Version: 1.0 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP do_hres() in the vDSO generic library masks the hw counter value immediately after reading it. Postpone the mask application after checking if the syscall fallback is enabled, in order to be able to detect a possible fallback for the architectures that have masks smaller than ULLONG_MAX. Signed-off-by: Vincenzo Frascino --- lib/vdso/gettimeofday.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index ef28cc5d7bff..ee1221ba1d32 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -35,12 +35,12 @@ static int do_hres(const struct vdso_data *vd, clockid_t clk, do { seq = vdso_read_begin(vd); - cycles = __arch_get_hw_counter(vd->clock_mode) & - vd->mask; + cycles = __arch_get_hw_counter(vd->clock_mode); ns = vdso_ts->nsec; last = vd->cycle_last; if (unlikely((s64)cycles < 0)) return clock_gettime_fallback(clk, ts); + cycles &= vd->mask; if (cycles > last) ns += (cycles - last) * vd->mult; ns >>= vd->shift;