From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753163AbeE3LY1 (ORCPT ); Wed, 30 May 2018 07:24:27 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33287 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753088AbeE3LYW (ORCPT ); Wed, 30 May 2018 07:24:22 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, keescook@chromium.org, "John Stultz" , "Peter Zijlstra" , "Thomas Gleixner" , "Christoph Hellwig" , "Anna-Maria Gleixner" , "Ingo Molnar" , "Linus Torvalds" Date: Wed, 30 May 2018 11:52:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 050/153] hrtimer: Ensure POSIX compliance (relative CLOCK_REALTIME hrtimers) In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.102-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Anna-Maria Gleixner commit 48d0c9becc7f3c66874c100c126459a9da0fdced upstream. The POSIX specification defines that relative CLOCK_REALTIME timers are not affected by clock modifications. Those timers have to use CLOCK_MONOTONIC to ensure POSIX compliance. The introduction of the additional HRTIMER_MODE_PINNED mode broke this requirement for pinned timers. There is no user space visible impact because user space timers are not using pinned mode, but for consistency reasons this needs to be fixed. Check whether the mode has the HRTIMER_MODE_REL bit set instead of comparing with HRTIMER_MODE_ABS. Signed-off-by: Anna-Maria Gleixner Cc: Christoph Hellwig Cc: John Stultz Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: keescook@chromium.org Fixes: 597d0275736d ("timers: Framework for identifying pinned timers") Link: http://lkml.kernel.org/r/20171221104205.7269-7-anna-maria@linutronix.de Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings --- kernel/hrtimer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1200,7 +1200,12 @@ static void __hrtimer_init(struct hrtime cpu_base = &__raw_get_cpu_var(hrtimer_bases); - if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS) + /* + * POSIX magic: Relative CLOCK_REALTIME timers are not affected by + * clock modifications, so they needs to become CLOCK_MONOTONIC to + * ensure POSIX compliance. + */ + if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL) clock_id = CLOCK_MONOTONIC; base = hrtimer_clockid_to_base(clock_id);