From nobody Mon Sep 15 11:28:18 2025 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 13867C54EBD for ; Thu, 12 Jan 2023 16:19:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229772AbjALQTn (ORCPT ); Thu, 12 Jan 2023 11:19:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236750AbjALQSi (ORCPT ); Thu, 12 Jan 2023 11:18:38 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B26B71CFF7 for ; Thu, 12 Jan 2023 08:14:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673540083; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZaDHq41SfAlEO/FEWzBquw15t81pf5rbinRD53jl+xU=; b=bNIoAgABqYHJs4fZK8qt/4ZS9cuc5gZnqU1dzQHJMw96b+MoGCxkg5968Zk5/mqZLFAXt0 pRREWdQmsNtHtWUoaV3Al8j8JjXQzVyT49pLn2S/57h6A2wIBwRduCz1YuWD6RySxr1HzQ k8VEHh19E1U+bHa6xtlQOgvjW0L5Evo= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-13--Cy6S057Or-Z-MOjx798qg-1; Thu, 12 Jan 2023 11:14:39 -0500 X-MC-Unique: -Cy6S057Or-Z-MOjx798qg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 219541C087A3; Thu, 12 Jan 2023 16:14:39 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.188]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3A502166B26; Thu, 12 Jan 2023 16:14:37 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Tejun Heo , Lai Jiangshan , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: [PATCH v8 1/5] workqueue: Protects wq_unbound_cpumask with wq_pool_attach_mutex Date: Thu, 12 Jan 2023 16:14:27 +0000 Message-Id: <20230112161431.860196-2-vschneid@redhat.com> In-Reply-To: <20230112161431.860196-1-vschneid@redhat.com> References: <20230112161431.860196-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Lai Jiangshan When unbind_workers() reads wq_unbound_cpumask to set the affinity of freshly-unbound kworkers, it only holds wq_pool_attach_mutex. This isn't sufficient as wq_unbound_cpumask is only protected by wq_pool_mutex. Make wq_unbound_cpumask protected with wq_pool_attach_mutex and also remove the need of temporary saved_cpumask. Fixes: 10a5a651e3af ("workqueue: Restrict kworker in the offline CPU pool r= unning on housekeeping CPUs") Reported-by: Valentin Schneider Signed-off-by: Lai Jiangshan --- kernel/workqueue.c | 41 ++++++++++++++++------------------------- 1 file changed, 16 insertions(+), 25 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 07895deca2711..76ea87b0251ce 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -326,7 +326,7 @@ static struct rcuwait manager_wait =3D __RCUWAIT_INITIA= LIZER(manager_wait); static LIST_HEAD(workqueues); /* PR: list of all workqueues */ static bool workqueue_freezing; /* PL: have wqs started freezing? */ =20 -/* PL: allowable cpus for unbound wqs and work items */ +/* PL&A: allowable cpus for unbound wqs and work items */ static cpumask_var_t wq_unbound_cpumask; =20 /* CPU where unbound work was last round robin scheduled from this CPU */ @@ -3952,7 +3952,8 @@ static void apply_wqattrs_cleanup(struct apply_wqattr= s_ctx *ctx) /* allocate the attrs and pwqs for later installation */ static struct apply_wqattrs_ctx * apply_wqattrs_prepare(struct workqueue_struct *wq, - const struct workqueue_attrs *attrs) + const struct workqueue_attrs *attrs, + const cpumask_var_t unbound_cpumask) { struct apply_wqattrs_ctx *ctx; struct workqueue_attrs *new_attrs, *tmp_attrs; @@ -3968,14 +3969,15 @@ apply_wqattrs_prepare(struct workqueue_struct *wq, goto out_free; =20 /* - * Calculate the attrs of the default pwq. + * Calculate the attrs of the default pwq with unbound_cpumask + * which is wq_unbound_cpumask or to set to wq_unbound_cpumask. * If the user configured cpumask doesn't overlap with the * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask. */ copy_workqueue_attrs(new_attrs, attrs); - cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask); + cpumask_and(new_attrs->cpumask, new_attrs->cpumask, unbound_cpumask); if (unlikely(cpumask_empty(new_attrs->cpumask))) - cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask); + cpumask_copy(new_attrs->cpumask, unbound_cpumask); =20 /* * We may create multiple pwqs with differing cpumasks. Make a @@ -4072,7 +4074,7 @@ static int apply_workqueue_attrs_locked(struct workqu= eue_struct *wq, wq->flags &=3D ~__WQ_ORDERED; } =20 - ctx =3D apply_wqattrs_prepare(wq, attrs); + ctx =3D apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask); if (!ctx) return -ENOMEM; =20 @@ -5334,7 +5336,7 @@ void thaw_workqueues(void) } #endif /* CONFIG_FREEZER */ =20 -static int workqueue_apply_unbound_cpumask(void) +static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpu= mask) { LIST_HEAD(ctxs); int ret =3D 0; @@ -5350,7 +5352,7 @@ static int workqueue_apply_unbound_cpumask(void) if (wq->flags & __WQ_ORDERED) continue; =20 - ctx =3D apply_wqattrs_prepare(wq, wq->unbound_attrs); + ctx =3D apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask); if (!ctx) { ret =3D -ENOMEM; break; @@ -5365,6 +5367,11 @@ static int workqueue_apply_unbound_cpumask(void) apply_wqattrs_cleanup(ctx); } =20 + if (!ret) { + mutex_lock(&wq_pool_attach_mutex); + cpumask_copy(wq_unbound_cpumask, unbound_cpumask); + mutex_unlock(&wq_pool_attach_mutex); + } return ret; } =20 @@ -5383,7 +5390,6 @@ static int workqueue_apply_unbound_cpumask(void) int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) { int ret =3D -EINVAL; - cpumask_var_t saved_cpumask; =20 /* * Not excluding isolated cpus on purpose. @@ -5397,23 +5403,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpum= ask) goto out_unlock; } =20 - if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) { - ret =3D -ENOMEM; - goto out_unlock; - } - - /* save the old wq_unbound_cpumask. */ - cpumask_copy(saved_cpumask, wq_unbound_cpumask); - - /* update wq_unbound_cpumask at first and apply it to wqs. */ - cpumask_copy(wq_unbound_cpumask, cpumask); - ret =3D workqueue_apply_unbound_cpumask(); - - /* restore the wq_unbound_cpumask when failed. */ - if (ret < 0) - cpumask_copy(wq_unbound_cpumask, saved_cpumask); + ret =3D workqueue_apply_unbound_cpumask(cpumask); =20 - free_cpumask_var(saved_cpumask); out_unlock: apply_wqattrs_unlock(); } --=20 2.31.1