From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752516AbdF0OfF (ORCPT ); Tue, 27 Jun 2017 10:35:05 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55884 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751620AbdF0OO3 (ORCPT ); Tue, 27 Jun 2017 10:14:29 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, John Stultz , Will Deacon , Daniel Mentz , Kevin Brodsky , Prarit Bhargava , Richard Cochran , Stephen Boyd , Miroslav Lichvar , Thomas Gleixner Subject: [PATCH 4.9 26/44] arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW Date: Tue, 27 Jun 2017 16:12:38 +0200 Message-Id: <20170627141109.807747498@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170627141107.865578528@linuxfoundation.org> References: <20170627141107.865578528@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 upstream. Recently vDSO support for CLOCK_MONOTONIC_RAW was added in 49eea433b326 ("arm64: Add support for CLOCK_MONOTONIC_RAW in clock_gettime() vDSO"). Noticing that the core timekeeping code never set tkr_raw.xtime_nsec, the vDSO implementation didn't bother exposing it via the data page and instead took the unshifted tk->raw_time.tv_nsec value which was then immediately shifted left in the vDSO code. Unfortunately, by accellerating the MONOTONIC_RAW clockid, it uncovered potential 1ns time inconsistencies caused by the timekeeping core not handing sub-ns resolution. Now that the core code has been fixed and is actually setting tkr_raw.xtime_nsec, we need to take that into account in the vDSO by adding it to the shifted raw_time value, in order to fix the user-visible inconsistency. Rather than do that at each use (and expand the data page in the process), instead perform the shift/addition operation when populating the data page and remove the shift from the vDSO code entirely. [jstultz: minor whitespace tweak, tried to improve commit message to make it more clear this fixes a regression] Reported-by: John Stultz Signed-off-by: Will Deacon Signed-off-by: John Stultz Tested-by: Daniel Mentz Acked-by: Kevin Brodsky Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: Miroslav Lichvar Link: http://lkml.kernel.org/r/1496965462-20003-4-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/vdso.c | 5 +++-- arch/arm64/kernel/vdso/gettimeofday.S | 1 - 2 files changed, 3 insertions(+), 3 deletions(-) --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -217,10 +217,11 @@ void update_vsyscall(struct timekeeper * /* tkr_mono.cycle_last == tkr_raw.cycle_last */ vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; vdso_data->raw_time_sec = tk->raw_time.tv_sec; - vdso_data->raw_time_nsec = tk->raw_time.tv_nsec; + vdso_data->raw_time_nsec = (tk->raw_time.tv_nsec << + tk->tkr_raw.shift) + + tk->tkr_raw.xtime_nsec; vdso_data->xtime_clock_sec = tk->xtime_sec; vdso_data->xtime_clock_nsec = tk->tkr_mono.xtime_nsec; - /* tkr_raw.xtime_nsec == 0 */ vdso_data->cs_mono_mult = tk->tkr_mono.mult; vdso_data->cs_raw_mult = tk->tkr_raw.mult; /* tkr_mono.shift == tkr_raw.shift */ --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -256,7 +256,6 @@ monotonic_raw: seqcnt_check fail=monotonic_raw /* All computations are done with left-shifted nsecs. */ - lsl x14, x14, x12 get_nsec_per_sec res=x9 lsl x9, x9, x12