From nobody Thu Jan 1 20:15:04 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 466A2CDB47E for ; Thu, 19 Oct 2023 00:15:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231599AbjJSAPX (ORCPT ); Wed, 18 Oct 2023 20:15:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229632AbjJSAPQ (ORCPT ); Wed, 18 Oct 2023 20:15:16 -0400 Received: from out162-62-57-210.mail.qq.com (out162-62-57-210.mail.qq.com [162.62.57.210]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D76E114 for ; Wed, 18 Oct 2023 17:15:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foxmail.com; s=s201512; t=1697674509; bh=hnxxIpZ8NjvfQ45DRLgFlfpkz9K7rWLl47wksLh86AY=; h=From:To:Subject:Date; b=fu9rVy88v3T1/hGl2JJFv3UE/gyolWc90RuwNpcE4yWVpIEIQHfMCz7tpFlByJ/il s2jM+IFwXU2ze0X+y7/hCb+1ZYsxZXk9ysedMY2qyvD+hucua1mRyGkPS9ZDWa/h3N PrPXsSFZVa7iGOCGl9ZeiaDWi7V7hDZeMQ7RuD7U= Received: from RT-NUC.. ([39.156.73.12]) by newxmesmtplogicsvrszb1-0.qq.com (NewEsmtp) with SMTP id 2DAA0C4A; Thu, 19 Oct 2023 08:11:26 +0800 X-QQ-mid: xmsmtpt1697674286tihb8ygf5 Message-ID: X-QQ-XMAILINFO: NiAdzfE16ND44TJ/oeIGmlBa/ESiFxlAPa2rvifXfxu47kULg2W/yRCHdaIjBp fU821CkTQSeMqlajNZOASck+jit4Bv8D+lnvI9JhdQKiOLgzdMpScUeGQtcYLb7X7pieUHR55Eih Sh9G0UNONQGUEYfm6sKkhoByvCxqM3/j3PcIng6UDw3aOPtsKlPh9JWfiRk0TVFJj6JLz1pk7Wdw QrljA31fjPbaUdyXNcQiuiMLoyjsM9YDw4p/NcH0GeZOBQeFByQ+1hZl8ToKbIBv7S9YEvQxPLsV cZhx/0AEIJGBsEPYRoZGiNVhVeaA2QJALbBNj475wyhzcOi4cIgGiF154n5nuGpdcZVGiuW85kQs gefeZGS0pAEtiThIm6CC78mqzEW5Y+v9VtTFxNpy8yp8FPBqYsNkW71oVwsW4yaICqpDOdFZkNcb EVZtYmfBy0xYxsnw5RXtA0qtg1Pae5Bdu2KtFtTQah3HebHk8CB1BPDvzJ1b2iu6poE8A2Ev+qvh 9cyQ9tab/dPdOhbVapLUVzXpV2ANz+5yhfKgPzobMwtcIMrpZegaI3LmX0fl6i4NlOGD5kfu8TV1 Figg3VHGrPphupYuFgPALhOhS9vAAq9a9ZVWVRN1ARvBq5s27jykHDCABYzmq8FHKU/cVkukRL5E +1U+fizpadtJ5pkyEmFt9lkL1EWNq0FPGsN9eex2Q5Cg4jPpFKoL4vHqpc1cpdkOK8zLrHQvIFR1 1C4JYrXLOj2ytZWEZJeKADu9hX7lcjVteFLZfOtLW5Mu478DoKYdvLROfC7nsqHU/CBwvS5TTz5q 1z3zGqCBAeLvmwnz1yDcZpfFvzFSeoe6naaBCk54OZaYDEhjUT9WZH5xkgIE5HcaNnGeTEtTS/c4 JiGH3WpWLHXQYvfa6J9H/4BYWXihg5UDwgGA/NEeDJoJM4FJ7ygmPqWfmtiXiyEjybPD28lzZvTi 5yR8u7/7dFZKbS5BLYAU9L/sNhIBvj X-QQ-XMRINFO: MPJ6Tf5t3I/ycC2BItcBVIA= From: Rong Tao To: elver@google.com, linux-kernel@vger.kernel.org, mark.rutland@arm.com, peterz@infradead.org, rongtao@cestc.cn, tglx@linutronix.de Subject: [PATCH v2] stop_machine: Avoid potential non-atomic read of multi_stop_data::state Date: Thu, 19 Oct 2023 08:11:23 +0800 X-OQ-MSGID: <20231019001123.289324-1-rtoax@foxmail.com> X-Mailer: git-send-email 2.42.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Rong Tao In commit b1fc58333575 ("stop_machine: Avoid potential race behaviour") fix both multi_cpu_stop() and set_state() access multi_stop_data::state, Pass curstate as a parameter to ack_state(), to avoid the non-atomic read. And replace smp_wmb()+WRITE_ONCE() with smp_store_release(). Signed-off-by: Rong Tao --- v1: stop_machine: Avoid potential race behaviour of multi_stop_data::state https://lore.kernel.org/lkml/tencent_705C16DF25978ACAEBD1E83E2288819010= 06@qq.com/ --- kernel/stop_machine.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index cedb17ba158a..35a122ce2cbd 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -183,15 +183,15 @@ static void set_state(struct multi_stop_data *msdata, { /* Reset ack counter. */ atomic_set(&msdata->thread_ack, msdata->num_threads); - smp_wmb(); - WRITE_ONCE(msdata->state, newstate); + smp_store_release(&msdata->state, newstate); } =20 /* Last one to ack a state moves to the next state. */ -static void ack_state(struct multi_stop_data *msdata) +static void ack_state(struct multi_stop_data *msdata, + enum multi_stop_state curstate) { if (atomic_dec_and_test(&msdata->thread_ack)) - set_state(msdata, msdata->state + 1); + set_state(msdata, curstate + 1); } =20 notrace void __weak stop_machine_yield(const struct cpumask *cpumask) @@ -242,7 +242,7 @@ static int multi_cpu_stop(void *data) default: break; } - ack_state(msdata); + ack_state(msdata, curstate); } else if (curstate > MULTI_STOP_PREPARE) { /* * At this stage all other CPUs we depend on must spin --=20 2.42.0