From patchwork Mon Jan 9 13:33:13 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 40871 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp2162136wrt; Mon, 9 Jan 2023 05:42:29 -0800 (PST) X-Google-Smtp-Source: AMrXdXuzywL0ekiktUv3bTs4xIeICYj11ZGFogDQBTjh6ShZiUjw/xmBDaim8Ir0LVIQAORFXOec X-Received: by 2002:a05:6402:221c:b0:498:b9ea:1896 with SMTP id cq28-20020a056402221c00b00498b9ea1896mr6003014edb.9.1673271748848; Mon, 09 Jan 2023 05:42:28 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1673271748; cv=none; d=google.com; s=arc-20160816; b=so1Xxd5eP2W5l6V2I8jjI7aNvV0T9aU03hT1oYSkWZqr1RIFd57YX7gMb/JYA2AHGd T+GgqccdRbfaaz0S8oP8YwzyzdIDrIFU4rhcQMSvGehRKd/LGxmGwo/voIkTm1t+v9xu HNzd8md1c139rzPv0YRS/uLYQPHKlLTdUg3lFOl9UEA2z9+nGM4mQFLQ1yTzLL4FvdLb 74MZp4eGntwmXPJY8+0jFmAT71ogoitCceLLWWRHZ/OXM8XEyc1MSB8nGnDwQ6Wyb0Al OQRymuUoNJbLm8vYPAvuann8vgc3la/e0tZMPZN82X8c23rwp0S7oS98WR+FH8fZhPCK 6syQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=ZaDHq41SfAlEO/FEWzBquw15t81pf5rbinRD53jl+xU=; b=vwHwXPguw3TiVBA7XTjooIhd23phBy+cFWmkO5U/mPHV95vFc7+KFFZz9OAw8zdAUG rReqh/62N5o81rCyxG1m0jbAtC7A8zkwIrs4uT9ZNcyCBdgndpAhmpHecBnbPUSPvkuF qscvGB8ckH+ltUiCQNkngu7F0r738s51/Msy6BEQdFqY1wMq3qNUs9PvIYWuxA5z1Syr qtIeparoHUTrkcGZ1Y9IwuMDrRo0s3z60vFSm7oICvNDTWRCu2JmKXf1y5kgBXnLMnFd 7chEsRwE9HUqWca6k3oSTQqTXk4rY/dPKO4S+bL6bDv3Ax34Ixyf+F13yoc3GUwTUW4s M+zw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=SCcjkEdd; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id cq10-20020a056402220a00b0048544ebce3esi7814582edb.462.2023.01.09.05.42.04; Mon, 09 Jan 2023 05:42:28 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=SCcjkEdd; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237171AbjAINfo (ORCPT + 99 others); Mon, 9 Jan 2023 08:35:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237040AbjAINe0 (ORCPT ); Mon, 9 Jan 2023 08:34:26 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 864A71EECD for ; Mon, 9 Jan 2023 05:33:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673271220; 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=SCcjkEddG1ojWO09dsfd6XtUK/H0A4bWNBFVua0tlprWGv/iphcFHYHsSo3q5lItt1dC1c GXK9tholLi/wSGeLGefN5JV755Pro2HRcn2g+lQiEkS+IFonbrlco7i6PuIB9A5JmOzrGD jZVo1c6/qgQtfG/9XaCuG1RzvW1Kq74= 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-342-RsS6eexYMW60mhY2Rmr8rQ-1; Mon, 09 Jan 2023 08:33:30 -0500 X-MC-Unique: RsS6eexYMW60mhY2Rmr8rQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ACA141C068CA; Mon, 9 Jan 2023 13:33:29 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.188]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 30CBB492C3E; Mon, 9 Jan 2023 13:33:28 +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 v7 1/4] workqueue: Protects wq_unbound_cpumask with wq_pool_attach_mutex Date: Mon, 9 Jan 2023 13:33:13 +0000 Message-Id: <20230109133316.4026472-2-vschneid@redhat.com> In-Reply-To: <20230109133316.4026472-1-vschneid@redhat.com> References: <20230109133316.4026472-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754552597370397045?= X-GMAIL-MSGID: =?utf-8?q?1754552597370397045?= 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 running 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 = __RCUWAIT_INITIALIZER(manager_wait); static LIST_HEAD(workqueues); /* PR: list of all workqueues */ static bool workqueue_freezing; /* PL: have wqs started freezing? */ -/* 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; /* CPU where unbound work was last round robin scheduled from this CPU */ @@ -3952,7 +3952,8 @@ static void apply_wqattrs_cleanup(struct apply_wqattrs_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; /* - * 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); /* * We may create multiple pwqs with differing cpumasks. Make a @@ -4072,7 +4074,7 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, wq->flags &= ~__WQ_ORDERED; } - ctx = apply_wqattrs_prepare(wq, attrs); + ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask); if (!ctx) return -ENOMEM; @@ -5334,7 +5336,7 @@ void thaw_workqueues(void) } #endif /* CONFIG_FREEZER */ -static int workqueue_apply_unbound_cpumask(void) +static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask) { LIST_HEAD(ctxs); int ret = 0; @@ -5350,7 +5352,7 @@ static int workqueue_apply_unbound_cpumask(void) if (wq->flags & __WQ_ORDERED) continue; - ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs); + ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask); if (!ctx) { ret = -ENOMEM; break; @@ -5365,6 +5367,11 @@ static int workqueue_apply_unbound_cpumask(void) apply_wqattrs_cleanup(ctx); } + if (!ret) { + mutex_lock(&wq_pool_attach_mutex); + cpumask_copy(wq_unbound_cpumask, unbound_cpumask); + mutex_unlock(&wq_pool_attach_mutex); + } return ret; } @@ -5383,7 +5390,6 @@ static int workqueue_apply_unbound_cpumask(void) int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) { int ret = -EINVAL; - cpumask_var_t saved_cpumask; /* * Not excluding isolated cpus on purpose. @@ -5397,23 +5403,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) goto out_unlock; } - if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) { - ret = -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 = workqueue_apply_unbound_cpumask(); - - /* restore the wq_unbound_cpumask when failed. */ - if (ret < 0) - cpumask_copy(wq_unbound_cpumask, saved_cpumask); + ret = workqueue_apply_unbound_cpumask(cpumask); - free_cpumask_var(saved_cpumask); out_unlock: apply_wqattrs_unlock(); } From patchwork Mon Jan 9 13:33:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 40872 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp2162154wrt; Mon, 9 Jan 2023 05:42:31 -0800 (PST) X-Google-Smtp-Source: AMrXdXtEJr1/Kz9t4WsCeR0DgMvwn/hx9sVxM7Ym+4JBVWMA3BZr6h5hZkVy1jwSRya54BEfTCFX X-Received: by 2002:a05:6a20:6aa8:b0:b3:87f8:8387 with SMTP id bi40-20020a056a206aa800b000b387f88387mr48345303pzb.50.1673271751589; Mon, 09 Jan 2023 05:42:31 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1673271751; cv=none; d=google.com; s=arc-20160816; b=OYYIqEQddvXAFQ91zhGTCB1TQF/nZXx+G+i6KIwItchnwsv2Nmf70FvGtK3UE7Zxxw KF0dll7tAg3SG6RgTaqKEJJd1iE9aTDwdFspekDiiwld/Pqp4N92dg2XpWl0HKEkU9eZ P5BIMTz/mxaJ3zgEshiDdkuwy3ZDeiMz17EVymrP8ISFZA/XpPSHutfl0qClp4TgNvJ/ Qo5884FNCwwj5Yt222k3nxmU2QSRXkEHKWyWlunE1Kfsx81I+Ka1pg2BpoyYAYv/YjKD GPhdslXDwT2ZEkMKySt19RN1lEC9WvPPuslBWXT2h4Ux9IdhJxjH07PmCpPzLMlBO7fY PuMA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=A6dex5ykj17DwH3w2pApB0qEylWCN/cbwH7uv0L+wI0=; b=PNwIk8SY4gvBlFctr6rIOz4IIyCvVuJ3Ghub40e/ka51RDKmNm/6HVX6KGZe4Zeewc 6V8FlKrpOEdsHAWnaQaNsYwNUSWOL5AfLT5m715N2CVjh/aP9b5zaz4UKydcBSg0hVV1 Npra36G0DzxrH6xiXxiuBzXWSIF7Mt8J5Qy5HLBOEb3x6Os1QnUEJz+/2sDcnL9yyPGJ ks1VuzpdC4DFOzjVpywnBNFOkIvSKcOtt5OpW//SH1OZ0nbkczu+RJdH/r8M7a1Flrzv 9M62ryusM9dCC/XHQWaVeHB8L0/Iuzpk/yOR2rujUQiy1DseZuDDN/x0nu1tEu82yNXy kB3Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=Y3u1cFb5; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id r6-20020a635d06000000b004787836f4d6si8911238pgb.396.2023.01.09.05.42.19; Mon, 09 Jan 2023 05:42:31 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=Y3u1cFb5; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237211AbjAINfr (ORCPT + 99 others); Mon, 9 Jan 2023 08:35:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237060AbjAINe0 (ORCPT ); Mon, 9 Jan 2023 08:34:26 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 722861EC65 for ; Mon, 9 Jan 2023 05:33:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673271217; 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=A6dex5ykj17DwH3w2pApB0qEylWCN/cbwH7uv0L+wI0=; b=Y3u1cFb5PF8ei9IE9Em3imoYQO2smeqeMPeFW09ejPK17BBzTPoTzqSXLpBnarnW0su77k TqkavTYSrbd1+eGQdGH6iXJ9qIcc/lIC810GI7F42HRdwAwGPbcCxyXZay0LaEBPUR9NYK vyl7NVHCiaoNnoJpXrI2OgMOZXhk6qk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-446-857qZRkRNAmGTjAEOm8Osw-1; Mon, 09 Jan 2023 08:33:32 -0500 X-MC-Unique: 857qZRkRNAmGTjAEOm8Osw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 95152196EF88; Mon, 9 Jan 2023 13:33:31 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.188]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 252CF492C1B; Mon, 9 Jan 2023 13:33:30 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Tejun Heo , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: [PATCH v7 2/4] workqueue: Factorize unbind/rebind_workers() logic Date: Mon, 9 Jan 2023 13:33:14 +0000 Message-Id: <20230109133316.4026472-3-vschneid@redhat.com> In-Reply-To: <20230109133316.4026472-1-vschneid@redhat.com> References: <20230109133316.4026472-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754552599842520922?= X-GMAIL-MSGID: =?utf-8?q?1754552599842520922?= Later patches will reuse this code, move it into reusable functions. Signed-off-by: Valentin Schneider Reviewed-by: Lai Jiangshan --- kernel/workqueue.c | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 76ea87b0251ce..5e6897f0ef105 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1972,6 +1972,23 @@ static struct worker *create_worker(struct worker_pool *pool) return NULL; } +static void unbind_worker(struct worker *worker) +{ + lockdep_assert_held(&wq_pool_attach_mutex); + + kthread_set_per_cpu(worker->task, -1); + if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask)) + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0); + else + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0); +} + +static void rebind_worker(struct worker *worker, struct worker_pool *pool) +{ + kthread_set_per_cpu(worker->task, pool->cpu); + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask) < 0); +} + /** * destroy_worker - destroy a workqueue worker * @worker: worker to be destroyed @@ -5008,13 +5025,8 @@ static void unbind_workers(int cpu) raw_spin_unlock_irq(&pool->lock); - for_each_pool_worker(worker, pool) { - kthread_set_per_cpu(worker->task, -1); - if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask)) - WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0); - else - WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0); - } + for_each_pool_worker(worker, pool) + unbind_worker(worker); mutex_unlock(&wq_pool_attach_mutex); } @@ -5039,11 +5051,8 @@ static void rebind_workers(struct worker_pool *pool) * of all workers first and then clear UNBOUND. As we're called * from CPU_ONLINE, the following shouldn't fail. */ - for_each_pool_worker(worker, pool) { - kthread_set_per_cpu(worker->task, pool->cpu); - WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, - pool->attrs->cpumask) < 0); - } + for_each_pool_worker(worker, pool) + rebind_worker(worker, pool); raw_spin_lock_irq(&pool->lock); From patchwork Mon Jan 9 13:33:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 40869 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp2162057wrt; Mon, 9 Jan 2023 05:42:16 -0800 (PST) X-Google-Smtp-Source: AMrXdXtb/kXd+YcEKOzg8lgG0wYk+bhVpeYDb6Fnlv2s/JIf97bA3StwlFKmnvLfGhGoWUfq+qfr X-Received: by 2002:a17:90a:a08c:b0:223:4bfe:f215 with SMTP id r12-20020a17090aa08c00b002234bfef215mr69824121pjp.15.1673271736085; Mon, 09 Jan 2023 05:42:16 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1673271736; cv=none; d=google.com; s=arc-20160816; b=HmBpt5IdarXGDVeHPomKP+rsF6sQUd+P0QDTVM3OLE5GjXQXMiHLWUbotLkZ+XWgxC BP30m5e+Q0eaZy6ZBtJTudrz5hcifmiLKMhgGx5NEHB9WJhjbHH0FIT73zZXCMeHEVrY ztdSC1joTm7IJs8t6WgBlThdbGiGW7ZXXkb8rQycsCJpetqcV36XlymTbTWQ0BN2AEM4 GM+/VnSUjDrHbi3r533M+/jNMOR8Ox2U+0zeQMsaQonM5+ZnLUp2ON5iEIhXRDoOke8X fXHE7UL9+xm9Mcswrh8cRcPi9CF2OGpUngWSTV/hBAaEfTGod7gr+ab1abqsUiUwEJkT LmxA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=M+u4Yp6HqrGg892XXKwAhCAa+wsoXpoco+d++RmvpiA=; b=GZxvdERrtzhskiT9AXq5jgrDyeFtLLknVPOueTYOs60BUhDBRP4c0GMny/jG6TexFP iQ0P5JTxd7EZOYHtcubLy/7lkFTHSmhjT27+zDC2SPSkPYPJxcwcotc71Z79YD2iBn2s AJUr+9y3LqhNH5rTclAoKGQtwrIIgrJmKUkHQ9WGhylVvwFTMY+Z+X69fXREascXBouW s3iGIJ51to4PnkRnRg7gOH25R9/Z62xg9zsbLt8URN1noqQBOApQMpJHTWfKraGBzVS9 SnQ9pku7WoM7jbUTBo1wqfjA1ScxZOPdE2fqSwRbEKc3ri3DKUS5cGXvZUvT65ar1AEp J0pg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=FD280BBH; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id 4-20020a631544000000b00476e62744a8si8816038pgv.388.2023.01.09.05.42.03; Mon, 09 Jan 2023 05:42:16 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=FD280BBH; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237133AbjAINfk (ORCPT + 99 others); Mon, 9 Jan 2023 08:35:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45940 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237044AbjAINe0 (ORCPT ); Mon, 9 Jan 2023 08:34:26 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 132753218C for ; Mon, 9 Jan 2023 05:33:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673271216; 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=M+u4Yp6HqrGg892XXKwAhCAa+wsoXpoco+d++RmvpiA=; b=FD280BBHGAD01Ohx9ihJYbPpdWYCHvoMbz5GY2UwqI+XOcgD9+zu7JpirWyehGktQ4E2Nc ZD+hIVTyYlG0ih7ftlsiykq9M+Yklf8punSy7L9es1uok/7OCUdXK/rym9LeqvhJYhEQGB VZte639UON3j98obZixws5vF8knyKyI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-590-s7fTy30bPIewYWhc49srOQ-1; Mon, 09 Jan 2023 08:33:33 -0500 X-MC-Unique: s7fTy30bPIewYWhc49srOQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CB0EF85C6E4; Mon, 9 Jan 2023 13:33:32 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.188]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C9A05492C14; Mon, 9 Jan 2023 13:33:31 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Tejun Heo , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: [PATCH v7 3/4] workqueue: Convert the idle_timer to a timer + work_struct Date: Mon, 9 Jan 2023 13:33:15 +0000 Message-Id: <20230109133316.4026472-4-vschneid@redhat.com> In-Reply-To: <20230109133316.4026472-1-vschneid@redhat.com> References: <20230109133316.4026472-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754552583793437444?= X-GMAIL-MSGID: =?utf-8?q?1754552583793437444?= A later patch will require a sleepable context in the idle worker timeout function. Converting worker_pool.idle_timer to a delayed_work gives us just that, however this would imply turning all idle_timer expiries into scheduler events (waking up a worker to handle the dwork). Instead, implement a "custom dwork" where the timer callback does some extra checks before queuing the associated work. No change in functionality intended. Signed-off-by: Valentin Schneider Reviewed-by: Lai Jiangshan --- kernel/workqueue.c | 52 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 50 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5e6897f0ef105..11bb657059bcd 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -169,7 +169,9 @@ struct worker_pool { struct list_head idle_list; /* L: list of idle workers */ struct timer_list idle_timer; /* L: worker idle timeout */ - struct timer_list mayday_timer; /* L: SOS timer for workers */ + struct work_struct idle_cull_work; /* L: worker idle cleanup */ + + struct timer_list mayday_timer; /* L: SOS timer for workers */ /* a workers is either on busy_hash or idle_list, or the manager */ DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); @@ -2019,17 +2021,61 @@ static void destroy_worker(struct worker *worker) wake_up_process(worker->task); } +/** + * idle_worker_timeout - check if some idle workers can now be deleted. + * @t: The pool's idle_timer that just expired + * + * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in + * worker_leave_idle(), as a worker flicking between idle and active while its + * pool is at the too_many_workers() tipping point would cause too much timer + * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let + * it expire and re-evaluate things from there. + */ static void idle_worker_timeout(struct timer_list *t) { struct worker_pool *pool = from_timer(pool, t, idle_timer); + bool do_cull = false; + + if (work_pending(&pool->idle_cull_work)) + return; raw_spin_lock_irq(&pool->lock); - while (too_many_workers(pool)) { + if (too_many_workers(pool)) { struct worker *worker; unsigned long expires; /* idle_list is kept in LIFO order, check the last one */ + worker = list_entry(pool->idle_list.prev, struct worker, entry); + expires = worker->last_active + IDLE_WORKER_TIMEOUT; + do_cull = !time_before(jiffies, expires); + + if (!do_cull) + mod_timer(&pool->idle_timer, expires); + } + raw_spin_unlock_irq(&pool->lock); + + if (do_cull) + queue_work(system_unbound_wq, &pool->idle_cull_work); +} + +/** + * idle_cull_fn - cull workers that have been idle for too long. + * @work: the pool's work for handling these idle workers + * + * This goes through a pool's idle workers and gets rid of those that have been + * idle for at least IDLE_WORKER_TIMEOUT seconds. + */ +static void idle_cull_fn(struct work_struct *work) +{ + struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work); + + raw_spin_lock_irq(&pool->lock); + + while (too_many_workers(pool)) { + struct worker *worker; + unsigned long expires; + worker = list_entry(pool->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; @@ -3479,6 +3525,7 @@ static int init_worker_pool(struct worker_pool *pool) hash_init(pool->busy_hash); timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE); + INIT_WORK(&pool->idle_cull_work, idle_cull_fn); timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0); @@ -3626,6 +3673,7 @@ static void put_unbound_pool(struct worker_pool *pool) /* shut down the timers */ del_timer_sync(&pool->idle_timer); + cancel_work_sync(&pool->idle_cull_work); del_timer_sync(&pool->mayday_timer); /* RCU protected to allow dereferences from get_work_pool() */ From patchwork Mon Jan 9 13:33:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 40870 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp2162051wrt; Mon, 9 Jan 2023 05:42:15 -0800 (PST) X-Google-Smtp-Source: AMrXdXsovfRvi4V2KGHZR4Xdy+4iQb3dvXy2pRHRIRI9y71WKS1U5DXtuyduheoRrU5BcnQoyXiK X-Received: by 2002:a05:6a21:2d05:b0:a7:92f2:9b65 with SMTP id tw5-20020a056a212d0500b000a792f29b65mr82382727pzb.59.1673271735566; Mon, 09 Jan 2023 05:42:15 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1673271735; cv=none; d=google.com; s=arc-20160816; b=ZU5YS+uv3sD7XMMn2uGf5sSWYAWcByEunX2aYU4NRJUX12Xky9kRS1mlsl+31/pGko gMaob5xFyQ0RODy6wP8gQqQYP2xjNjfwIG+srQTh8XJ8VqRGXb66eUGVwQYg6kIpYbsG bMLtuK0vv2xsb4QaAO42Zljnpvk+ABp+if/G1xRiQCSYCmODmyFu+H7BZlfDKhfjUO83 B8h6te+R29M0cjQWtuo8MGu9frCFBYLZweEvp/JbcU66E4CI1KcIDr8L8SX13I0xB+wW wbpEbwzbli8DJQwGnc4/8rxUoQYSivEBjO5yq4EOe3PCtiovx2X960L34r93dolyI6Ke xc8Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=/6M3Rob2RC/Aka2tK9LaptMexQaAS/cOrNB1YXRrEio=; b=VbRqgG2DM2OtsnP6pODsm10CWwA0Zddv4TFJQWU9hgBZaJgCSWJrQN1tsQ4Co/1W0P 0jMggtEtGuQG6+GK0Dpr7kovt1QfYBA+B7FFeuBVeDLFTg9wmpNhxAo6PfBTE8FIasDC M4dP+A54b3QyqAEkdZzrODIVXI4lhDOjjf187MScjhYjN9Vl0ZcxoUbRzGypM7rVczdM tQ06+NB2IXWUxvUarFMDRtmXdFoyTxzd1B1+a6Zxb+6savIAJU0UgTMt1FHGm3brBNYO z3koSo3ZK68PEF8x2mNKX8jWAc4SUHhImg6UAoebrBhSgQanWrPKG638byMPy8mCnSd5 BPEg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=U6cC9tUf; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id h64-20020a638343000000b0046f1263abd6si9681920pge.661.2023.01.09.05.42.03; Mon, 09 Jan 2023 05:42:15 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=U6cC9tUf; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237111AbjAINfd (ORCPT + 99 others); Mon, 9 Jan 2023 08:35:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237048AbjAINe0 (ORCPT ); Mon, 9 Jan 2023 08:34:26 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EA4E1EC5E for ; Mon, 9 Jan 2023 05:33:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673271217; 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=/6M3Rob2RC/Aka2tK9LaptMexQaAS/cOrNB1YXRrEio=; b=U6cC9tUfJNEBU8uwnQ/uP8lfFzWWRK+mUXvk0unnJaA7vikS+1/HUTXvxOxpRMmDbsF1Ec j+/qS/cgaZqTbg6BzXQr+uP2Uzsz5n/z5kxoqaNhMGi8XvOx7d2Q+nER3dJ9urVDt+aC63 rKekBF5w7NIcxSefq2yntMbVTKyH4yg= 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-516-3l9WjZTTOrubJs7btB3-9w-1; Mon, 09 Jan 2023 08:33:34 -0500 X-MC-Unique: 3l9WjZTTOrubJs7btB3-9w-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1B7F91C068C7; Mon, 9 Jan 2023 13:33:34 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.188]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0B025492C14; Mon, 9 Jan 2023 13:33:32 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: [PATCH v7 4/4] workqueue: Unbind kworkers before sending them to exit() Date: Mon, 9 Jan 2023 13:33:16 +0000 Message-Id: <20230109133316.4026472-5-vschneid@redhat.com> In-Reply-To: <20230109133316.4026472-1-vschneid@redhat.com> References: <20230109133316.4026472-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754552583424730626?= X-GMAIL-MSGID: =?utf-8?q?1754552583424730626?= It has been reported that isolated CPUs can suffer from interference due to per-CPU kworkers waking up just to die. A surge of workqueue activity during initial setup of a latency-sensitive application (refresh_vm_stats() being one of the culprits) can cause extra per-CPU kworkers to be spawned. Then, said latency-sensitive task can be running merrily on an isolated CPU only to be interrupted sometime later by a kworker marked for death (cf. IDLE_WORKER_TIMEOUT, 5 minutes after last kworker activity). Prevent this by affining kworkers to the wq_unbound_cpumask (which doesn't contain isolated CPUs, cf. HK_TYPE_WQ) before waking them up after marking them with WORKER_DIE. Changing the affinity does require a sleepable context, leverage the newly introduced pool->idle_cull_work to get that. Remove dying workers from pool->workers and keep track of them in a separate list. This intentionally prevents for_each_loop_worker() from iterating over workers that are marked for death. Rename destroy_worker() to set_working_dying() to better reflect its effects and relationship with wake_dying_workers(). Signed-off-by: Valentin Schneider --- kernel/workqueue.c | 79 +++++++++++++++++++++++++++++++++++++++------- 1 file changed, 67 insertions(+), 12 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 11bb657059bcd..45f2187836c67 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -179,6 +179,7 @@ struct worker_pool { struct worker *manager; /* L: purely informational */ struct list_head workers; /* A: attached workers */ + struct list_head dying_workers; /* A: workers about to die */ struct completion *detach_completion; /* all workers detached */ struct ida worker_ida; /* worker IDs for task name */ @@ -1902,7 +1903,7 @@ static void worker_detach_from_pool(struct worker *worker) list_del(&worker->node); worker->pool = NULL; - if (list_empty(&pool->workers)) + if (list_empty(&pool->workers) && list_empty(&pool->dying_workers)) detach_completion = pool->detach_completion; mutex_unlock(&wq_pool_attach_mutex); @@ -1991,21 +1992,44 @@ static void rebind_worker(struct worker *worker, struct worker_pool *pool) WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask) < 0); } +static void wake_dying_workers(struct list_head *cull_list) +{ + struct worker *worker, *tmp; + + list_for_each_entry_safe(worker, tmp, cull_list, entry) { + list_del_init(&worker->entry); + unbind_worker(worker); + /* + * If the worker was somehow already running, then it had to be + * in pool->idle_list when set_worker_dying() happened or we + * wouldn't have gotten here. + * + * Thus, the worker must either have observed the WORKER_DIE + * flag, or have set its state to TASK_IDLE. Either way, the + * below will be observed by the worker and is safe to do + * outside of pool->lock. + */ + wake_up_process(worker->task); + } +} + /** - * destroy_worker - destroy a workqueue worker + * set_worker_dying - Tag a worker for destruction * @worker: worker to be destroyed + * @list: transfer worker away from its pool->idle_list and into list * - * Destroy @worker and adjust @pool stats accordingly. The worker should - * be idle. + * Tag @worker for destruction and adjust @pool stats accordingly. The worker + * should be idle. * * CONTEXT: * raw_spin_lock_irq(pool->lock). */ -static void destroy_worker(struct worker *worker) +static void set_worker_dying(struct worker *worker, struct list_head *list) { struct worker_pool *pool = worker->pool; lockdep_assert_held(&pool->lock); + lockdep_assert_held(&wq_pool_attach_mutex); /* sanity check frenzy */ if (WARN_ON(worker->current_work) || @@ -2016,9 +2040,10 @@ static void destroy_worker(struct worker *worker) pool->nr_workers--; pool->nr_idle--; - list_del_init(&worker->entry); worker->flags |= WORKER_DIE; - wake_up_process(worker->task); + + list_move(&worker->entry, list); + list_move(&worker->node, &pool->dying_workers); } /** @@ -2065,11 +2090,24 @@ static void idle_worker_timeout(struct timer_list *t) * * This goes through a pool's idle workers and gets rid of those that have been * idle for at least IDLE_WORKER_TIMEOUT seconds. + * + * We don't want to disturb isolated CPUs because of a pcpu kworker being + * culled, so this also resets worker affinity. This requires a sleepable + * context, hence the split between timer callback and work item. */ static void idle_cull_fn(struct work_struct *work) { struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work); + struct list_head cull_list; + INIT_LIST_HEAD(&cull_list); + /* + * Grabbing wq_pool_attach_mutex here ensures an already-running worker + * cannot proceed beyong worker_detach_from_pool() in its self-destruct + * path. This is required as a previously-preempted worker could run after + * set_worker_dying() has happened but before wake_dying_workers() did. + */ + mutex_lock(&wq_pool_attach_mutex); raw_spin_lock_irq(&pool->lock); while (too_many_workers(pool)) { @@ -2084,10 +2122,12 @@ static void idle_cull_fn(struct work_struct *work) break; } - destroy_worker(worker); + set_worker_dying(worker, &cull_list); } raw_spin_unlock_irq(&pool->lock); + wake_dying_workers(&cull_list); + mutex_unlock(&wq_pool_attach_mutex); } static void send_mayday(struct work_struct *work) @@ -2451,12 +2491,12 @@ static int worker_thread(void *__worker) /* am I supposed to die? */ if (unlikely(worker->flags & WORKER_DIE)) { raw_spin_unlock_irq(&pool->lock); - WARN_ON_ONCE(!list_empty(&worker->entry)); set_pf_worker(false); set_task_comm(worker->task, "kworker/dying"); ida_free(&pool->worker_ida, worker->id); worker_detach_from_pool(worker); + WARN_ON_ONCE(!list_empty(&worker->entry)); kfree(worker); return 0; } @@ -3530,6 +3570,7 @@ static int init_worker_pool(struct worker_pool *pool) timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0); INIT_LIST_HEAD(&pool->workers); + INIT_LIST_HEAD(&pool->dying_workers); ida_init(&pool->worker_ida); INIT_HLIST_NODE(&pool->hash_node); @@ -3630,8 +3671,11 @@ static bool wq_manager_inactive(struct worker_pool *pool) static void put_unbound_pool(struct worker_pool *pool) { DECLARE_COMPLETION_ONSTACK(detach_completion); + struct list_head cull_list; struct worker *worker; + INIT_LIST_HEAD(&cull_list); + lockdep_assert_held(&wq_pool_mutex); if (--pool->refcnt) @@ -3658,13 +3702,24 @@ static void put_unbound_pool(struct worker_pool *pool) TASK_UNINTERRUPTIBLE); pool->flags |= POOL_MANAGER_ACTIVE; + /* + * We need to hold wq_pool_attach_mutex() while destroying the workers, + * but we can't grab it in rcuwait_wait_event() as it can clobber + * current's task state. We can drop pool->lock here as we've set + * POOL_MANAGER_ACTIVE, no one else can steal our manager position. + */ + raw_spin_unlock_irq(&pool->lock); + mutex_lock(&wq_pool_attach_mutex); + raw_spin_lock_irq(&pool->lock); + while ((worker = first_idle_worker(pool))) - destroy_worker(worker); + set_worker_dying(worker, &cull_list); WARN_ON(pool->nr_workers || pool->nr_idle); raw_spin_unlock_irq(&pool->lock); - mutex_lock(&wq_pool_attach_mutex); - if (!list_empty(&pool->workers)) + wake_dying_workers(&cull_list); + + if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers)) pool->detach_completion = &detach_completion; mutex_unlock(&wq_pool_attach_mutex);