From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A126BECE597 for ; Sat, 12 Oct 2019 06:52:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A4B42067B for ; Sat, 12 Oct 2019 06:52:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728993AbfJLGwX (ORCPT ); Sat, 12 Oct 2019 02:52:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47568 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727117AbfJLGwX (ORCPT ); Sat, 12 Oct 2019 02:52:23 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3BDCD3082B02; Sat, 12 Oct 2019 06:52:23 +0000 (UTC) Received: from t460p.redhat.com (ovpn-117-172.phx2.redhat.com [10.3.117.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6301060A97; Sat, 12 Oct 2019 06:52:22 +0000 (UTC) From: Scott Wood To: Sebastian Andrzej Siewior Cc: Thomas Gleixner , Steven Rostedt , Peter Zijlstra , Juri Lelli , Waiman Long , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Scott Wood Subject: [PATCH RT v2 3/3] sched: migrate_enable: Use stop_one_cpu_nowait() Date: Sat, 12 Oct 2019 01:52:14 -0500 Message-Id: <20191012065214.28109-4-swood@redhat.com> In-Reply-To: <20191012065214.28109-1-swood@redhat.com> References: <20191012065214.28109-1-swood@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Sat, 12 Oct 2019 06:52:23 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org migrate_enable() can be called with current->state != TASK_RUNNING. Avoid clobbering the existing state by using stop_one_cpu_nowait(). Since we're stopping the current cpu, we know that we won't get past __schedule() until migration_cpu_stop() has run (at least up to the point of migrating us to another cpu). Signed-off-by: Scott Wood --- include/linux/stop_machine.h | 2 ++ kernel/sched/core.c | 22 +++++++++++++--------- kernel/stop_machine.c | 7 +++++-- 3 files changed, 20 insertions(+), 11 deletions(-) diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 6d3635c86dbe..82fc686ddd9e 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -26,6 +26,8 @@ struct cpu_stop_work { cpu_stop_fn_t fn; void *arg; struct cpu_stop_done *done; + /* Did not run due to disabled stopper; for nowait debug checks */ + bool disabled; }; int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5cb2a519b8bf..6383ade320f2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1051,6 +1051,7 @@ static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, struct migration_arg { struct task_struct *task; int dest_cpu; + bool done; }; /* @@ -1086,6 +1087,11 @@ static int migration_cpu_stop(void *data) struct task_struct *p = arg->task; struct rq *rq = this_rq(); struct rq_flags rf; + int dest_cpu = arg->dest_cpu; + + /* We don't look at arg after this point. */ + smp_mb(); + arg->done = true; /* * The original target CPU might have gone down and we might @@ -1108,9 +1114,9 @@ static int migration_cpu_stop(void *data) */ if (task_rq(p) == rq) { if (task_on_rq_queued(p)) - rq = __migrate_task(rq, &rf, p, arg->dest_cpu); + rq = __migrate_task(rq, &rf, p, dest_cpu); else - p->wake_cpu = arg->dest_cpu; + p->wake_cpu = dest_cpu; } rq_unlock(rq, &rf); raw_spin_unlock(&p->pi_lock); @@ -7392,6 +7398,7 @@ void migrate_enable(void) WARN_ON(smp_processor_id() != cpu); if (!is_cpu_allowed(p, cpu)) { struct migration_arg arg = { p }; + struct cpu_stop_work work; struct rq_flags rf; rq = task_rq_lock(p, &rf); @@ -7399,13 +7406,10 @@ void migrate_enable(void) arg.dest_cpu = select_fallback_rq(cpu, p); task_rq_unlock(rq, p, &rf); - preempt_lazy_enable(); - preempt_enable(); - - sleeping_lock_inc(); - stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); - sleeping_lock_dec(); - return; + stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, + &arg, &work); + __schedule(true); + WARN_ON_ONCE(!arg.done && !work.disabled); } out: diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 2b5a6754646f..fa53a472dd44 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -85,8 +85,11 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) enabled = stopper->enabled; if (enabled) __cpu_stop_queue_work(stopper, work, &wakeq); - else if (work->done) - cpu_stop_signal_done(work->done); + else { + work->disabled = true; + if (work->done) + cpu_stop_signal_done(work->done); + } raw_spin_unlock_irqrestore(&stopper->lock, flags); wake_up_q(&wakeq); -- 1.8.3.1