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[2620:137:e000::1:20]) by mx.google.com with ESMTP id ay16-20020a056a00301000b005730a1bbac0si11900961pfb.354.2022.11.28.10.42.26; Mon, 28 Nov 2022 10:42:39 -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=ecnWwGyo; 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 S232802AbiK1Se0 (ORCPT + 99 others); Mon, 28 Nov 2022 13:34:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233410AbiK1Sd7 (ORCPT ); Mon, 28 Nov 2022 13:33:59 -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 61168274 for ; Mon, 28 Nov 2022 10:31:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669660286; 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=iBeA7STGfam5IOKxD+wB1RjgRxQP91bo13x/HX7w5mQ=; b=ecnWwGyomCgz+xuQUlohCqXMHG7Ex9vSOD/QgQDYPdCkHOxXLU59P5aVgqprI8/bT1dOr4 g3MsTHvg1+OAxDwaiKxX0G6GOumOFp39uYH598sowPKkeGyzly+Ayoz7P/8wHXg1lHV6j7 dgEAIt94vXNWxG09J/9+a8B4pdEg8IM= 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-351-UVzXAoVYOQ6S6tCp3ERLqA-1; Mon, 28 Nov 2022 13:31:22 -0500 X-MC-Unique: UVzXAoVYOQ6S6tCp3ERLqA-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 C2E35800186; Mon, 28 Nov 2022 18:31:21 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.37.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id C436E2166B2E; Mon, 28 Nov 2022 18:31:20 +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 v6 3/4] workqueue: Convert the idle_timer to a timer + work_struct Date: Mon, 28 Nov 2022 18:31:08 +0000 Message-Id: <20221128183109.446754-4-vschneid@redhat.com> In-Reply-To: <20221128183109.446754-1-vschneid@redhat.com> References: <20221128183109.446754-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 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?1750766410233623995?= X-GMAIL-MSGID: =?utf-8?q?1750766410233623995?= 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 --- kernel/workqueue.c | 51 +++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 48 insertions(+), 3 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 8185a42848c50..c8b1466a9c070 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); @@ -1806,7 +1808,9 @@ static void worker_enter_idle(struct worker *worker) /* idle_list is LIFO */ list_add(&worker->entry, &pool->idle_list); - if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) + if (too_many_workers(pool) && + !timer_pending(&pool->idle_timer) && + !work_pending(&pool->idle_cull_work)) mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); /* Sanity check nr_running. */ @@ -2019,17 +2023,56 @@ static void destroy_worker(struct worker *worker) wake_up_process(worker->task); } +/* + * idle_worker_timeout - check if some idle workers can now be deleted. + * + * 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. + */ +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 +3522,7 @@ 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 +3670,7 @@ 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() */