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=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 EA834C33C9E for ; Fri, 17 Jan 2020 17:42:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD94A2467D for ; Fri, 17 Jan 2020 17:42:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729423AbgAQRlz (ORCPT ); Fri, 17 Jan 2020 12:41:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:40136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729285AbgAQRld (ORCPT ); Fri, 17 Jan 2020 12:41:33 -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 3817624694; Fri, 17 Jan 2020 17:41:33 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1isVci-000Qc5-4u; Fri, 17 Jan 2020 12:41:32 -0500 Message-Id: <20200117174132.033584043@goodmis.org> User-Agent: quilt/0.65 Date: Fri, 17 Jan 2020 12:41:42 -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 Subject: [PATCH RT 31/32] sched: migrate_enable: Busy loop until the migration request is completed References: <20200117174111.282847363@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 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-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior [ Upstream commit 140d7f54a5fff02898d2ca9802b39548bf7455f1 ] If user task changes the CPU affinity mask of a running task it will dispatch migration request if the current CPU is no longer allowed. This might happen shortly before a task enters a migrate_disable() section. Upon leaving the migrate_disable() section, the task will notice that the current CPU is no longer allowed and will will dispatch its own migration request to move it off the current CPU. While invoking __schedule() the first migration request will be processed and the task returns on the "new" CPU with "arg.done = 0". Its own migration request will be processed shortly after and will result in memory corruption if the stack memory, designed for request, was used otherwise in the meantime. Spin until the migration request has been processed if it was accepted. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- kernel/sched/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index cbd76324babd..4616c086dd26 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7329,7 +7329,7 @@ void migrate_enable(void) WARN_ON(smp_processor_id() != cpu); if (!is_cpu_allowed(p, cpu)) { - struct migration_arg arg = { p }; + struct migration_arg arg = { .task = p }; struct cpu_stop_work work; struct rq_flags rf; @@ -7342,7 +7342,10 @@ void migrate_enable(void) &arg, &work); tlb_migrate_finish(p->mm); __schedule(true); - WARN_ON_ONCE(!arg.done && !work.disabled); + if (!work.disabled) { + while (!arg.done) + cpu_relax(); + } } out: -- 2.24.1