Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754105AbaGVLaN (ORCPT ); Tue, 22 Jul 2014 07:30:13 -0400 Received: from relay.parallels.com ([195.214.232.42]:55826 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753841AbaGVLaL (ORCPT ); Tue, 22 Jul 2014 07:30:11 -0400 Message-ID: <1406028601.3526.18.camel@tkhai> Subject: [PATCH 0/5] sched: Add on_rq states and remove several double rq locks From: Kirill Tkhai To: CC: Peter Zijlstra , Mike Galbraith , Steven Rostedt , Tim Chen , Nicolas Pitre , "Ingo Molnar" , Paul Turner , Date: Tue, 22 Jul 2014 15:30:01 +0400 Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This series aims to get rid of some places where locks of two RQs are held at the same time. Patch [1/5] is a preparation/cleanup. It replaces old (.on_rq == 1) with new (.on_rq == ONRQ_QUEUED) everywhere. No functional changes. Patch [2/5] is main in the series. It introduces new state: ONRQ_MIGRATING and teaches scheduler to understand it (we need a little changes predominantly in try_to_wake_up()). This will be used in the following way: (we are changing task's rq) raw_spin_lock(&src_rq->lock); dequeue_task(src_rq, p, 0); p->on_rq = ONRQ_MIGRATING; set_task_cpu(p, dst_cpu); raw_spin_unlock(&src_rq->lock); raw_spin_lock(&dst_rq->lock); p->on_rq = ONRQ_QUEUED; enqueue_task(dst_rq, p, 0); raw_spin_unlock(&dst_rq->lock); Patches [3-5/5] remove double locks and use new ONRQ_MIGRATING state. They allow unlocked using of 3-4 function, which looks safe for me. The series doesn't add any overhead, and it shouldn't worsen performance, I think. It improves granularity, and it's possible to imagine situations, which will be happier without double rq lock. I tested the reliability for 2-3 week (in sum, with breaks) on my work laptop, and bugs did not happen. Looks like, it's ready for people's review. Commentaries are welcome. Thanks! --- Kirill Tkhai (5): sched: Wrapper for checking task_struct's .on_rq sched: Teach scheduler to understand ONRQ_MIGRATING state sched: Remove double_rq_lock() from __migrate_task() sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop() sched/fair: Remove double_lock_balance() from load_balance() kernel/sched/core.c | 109 +++++++++++++++++++------------- kernel/sched/deadline.c | 14 ++-- kernel/sched/fair.c | 156 +++++++++++++++++++++++++++++----------------- kernel/sched/rt.c | 16 ++--- kernel/sched/sched.h | 8 ++ kernel/sched/stop_task.c | 2 - 6 files changed, 187 insertions(+), 118 deletions(-) -- Signed-off-by: Kirill Tkhai -- 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/