Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754460AbaGIGzu (ORCPT ); Wed, 9 Jul 2014 02:55:50 -0400 Received: from mail-qg0-f41.google.com ([209.85.192.41]:38735 "EHLO mail-qg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751542AbaGIGzt (ORCPT ); Wed, 9 Jul 2014 02:55:49 -0400 From: Viresh Kumar To: tglx@linutronix.de Cc: linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, arvind.chauhan@arm.com, preeti@linux.vnet.ibm.com, khilman@linaro.org, Viresh Kumar , Darren Hart , "David S. Miller" , Ingo Molnar , netdev@vger.kernel.org, Peter Zijlstra Subject: [RFC 0/7] hrtimer: drop active hrtimer checks after adding it Date: Wed, 9 Jul 2014 12:25:32 +0530 Message-Id: X-Mailer: git-send-email 2.0.0.rc2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The only special case is when the hrtimer was in past. If it is getting enqueued to local CPUs's clock-base, we raise a softirq and exit, else we handle that on next interrupt on remote CPU. At several places in the kernel, we try to make sure if hrtimer was added properly or not by calling hrtimer_active(), like: hrtimer_start(timer, expires, mode); if (hrtimer_active(timer)) { /* Added successfully */ } else { /* Was added in the past */ } As hrtimer_start*() never fails, hrtimer_active() is guaranteed to return '1'. So, there is no point calling hrtimer_active(). First patch adds a WARN_ON_ONCE() to __hrtimer_start_range_ns() to make sure hrtimers are always enqueued from it. Next 6 patches update several parts of kernel to drop calls to hrtimer_active() after starting a hrtimer. Rebased over 3.16-rc4 and pushed here: git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git hrtimer/drop-hrtimer-active-calls Cc: Darren Hart Cc: "David S. Miller" Cc: Ingo Molnar Cc: netdev@vger.kernel.org Cc: Peter Zijlstra Viresh Kumar (7): hrtimer: Warn if hrtimer_start*() failed to enqueue hrtimer hrtimer: don't check for active hrtimer after adding it tick: don't check for active hrtimer after adding it sched: don't check for active hrtimer after adding it futex: don't check for active hrtimer after adding it rtmutex: don't check for active hrtimer after adding it net: don't check for active hrtimer after adding it kernel/futex.c | 5 +---- kernel/hrtimer.c | 6 ++---- kernel/locking/rtmutex.c | 5 +---- kernel/sched/core.c | 20 +++++++++----------- kernel/sched/deadline.c | 2 +- kernel/time/tick-sched.c | 45 ++++++++++++++++++--------------------------- net/core/pktgen.c | 2 -- 7 files changed, 32 insertions(+), 53 deletions(-) -- 2.0.0.rc2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/