From patchwork Sat Aug 8 02:03:22 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Lynch X-Patchwork-Id: 6973771 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 669AE9F457 for ; Sat, 8 Aug 2015 02:06:57 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8DEBB206D9 for ; Sat, 8 Aug 2015 02:06:56 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9A01B206A9 for ; Sat, 8 Aug 2015 02:06:55 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZNtUJ-000097-9k; Sat, 08 Aug 2015 02:03:55 +0000 Received: from relay1.mentorg.com ([192.94.38.131]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZNtUG-00007Z-CO for linux-arm-kernel@lists.infradead.org; Sat, 08 Aug 2015 02:03:53 +0000 Received: from svr-orw-fem-06.mgc.mentorg.com ([147.34.97.120]) by relay1.mentorg.com with esmtp id 1ZNtTr-0002OF-GL from Nathan_Lynch@mentor.com ; Fri, 07 Aug 2015 19:03:27 -0700 Received: from localhost (147.34.91.1) by svr-orw-fem-06.mgc.mentorg.com (147.34.97.120) with Microsoft SMTP Server (TLS) id 14.3.224.2; Fri, 7 Aug 2015 19:03:26 -0700 From: Nathan Lynch To: Subject: [PATCH 1/2] ARM: VDSO: fix coarse clock monotonicity regression Date: Fri, 7 Aug 2015 21:03:22 -0500 Message-ID: <1438999403-5770-2-git-send-email-nathan_lynch@mentor.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1438999403-5770-1-git-send-email-nathan_lynch@mentor.com> References: <1438999403-5770-1-git-send-email-nathan_lynch@mentor.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150807_190352_453506_4A461D90 X-CRM114-Status: GOOD ( 10.18 ) X-Spam-Score: -2.6 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: John Stultz , Thomas Gleixner , Russell King , linux-kernel@vger.kernel.org, Will Deacon Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last") it has become possible on ARM to: - Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp via syscall. - Subsequently obtain a timestamp for the same clock ID via VDSO which predates the first timestamp (by one jiffy). This is because ARM's update_vsyscall is deriving the coarse time using the __current_kernel_time interface, when it should really be using the timekeeper object provided to it by the timekeeping core. It happened to work before only because __current_kernel_time would access the same timekeeper object which had been passed to update_vsyscall. This is no longer the case. Signed-off-by: Nathan Lynch --- arch/arm/kernel/vdso.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index efe17dd9b921..c8b243c1aef8 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -296,7 +296,6 @@ static bool tk_is_cntvct(const struct timekeeper *tk) */ void update_vsyscall(struct timekeeper *tk) { - struct timespec xtime_coarse; struct timespec64 *wtm = &tk->wall_to_monotonic; if (!cntvct_ok) { @@ -308,10 +307,10 @@ void update_vsyscall(struct timekeeper *tk) vdso_write_begin(vdso_data); - xtime_coarse = __current_kernel_time(); vdso_data->tk_is_cntvct = tk_is_cntvct(tk); - vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec; - vdso_data->xtime_coarse_nsec = xtime_coarse.tv_nsec; + vdso_data->xtime_coarse_sec = tk->xtime_sec; + vdso_data->xtime_coarse_nsec = tk->tkr_mono.xtime_nsec >> + tk->tkr_mono.shift; vdso_data->wtm_clock_sec = wtm->tv_sec; vdso_data->wtm_clock_nsec = wtm->tv_nsec;