From patchwork Thu Jan 23 20:39:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 213261 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=unavailable 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 71219C33CAF for ; Thu, 23 Jan 2020 20:40:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B38E24691 for ; Thu, 23 Jan 2020 20:40:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729600AbgAWUkq (ORCPT ); Thu, 23 Jan 2020 15:40:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:45878 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729339AbgAWUjr (ORCPT ); Thu, 23 Jan 2020 15:39:47 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EC92524693; Thu, 23 Jan 2020 20:39:46 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1iujGT-000mfd-SX; Thu, 23 Jan 2020 15:39:45 -0500 Message-Id: <20200123203945.766477535@goodmis.org> User-Agent: quilt/0.65 Date: Thu, 23 Jan 2020 15:39:54 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Julia Cartwright , Daniel Wagner , Tom Zanussi , Scott Wood Subject: [PATCH RT 24/30] sched: migrate_enable: Use stop_one_cpu_nowait() References: <20200123203930.646725253@goodmis.org> MIME-Version: 1.0 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org 4.19.94-rt39-rc2 stable review patch. If anyone has any objections, please let me know. ------------------ From: Scott Wood [ Upstream commit 6b39a1fa8c53cae08dc03afdae193b7d3a78a173 ] 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 Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- include/linux/stop_machine.h | 2 ++ kernel/sched/core.c | 23 +++++++++++++---------- kernel/stop_machine.c | 7 +++++-- 3 files changed, 20 insertions(+), 12 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 e97ac751aad2..e465381b464d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -990,6 +990,7 @@ 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; }; /* @@ -1025,6 +1026,11 @@ 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 @@ -1047,9 +1053,9 @@ 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); @@ -7322,6 +7328,7 @@ 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); @@ -7329,15 +7336,11 @@ 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(); + stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, + &arg, &work); tlb_migrate_finish(p->mm); - - return; + __schedule(true); + WARN_ON_ONCE(!arg.done && !work.disabled); } out: diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 067cb83f37ea..2d15c0d50625 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -86,8 +86,11 @@ 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);