From patchwork Wed May 10 16:04:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johannes Berg X-Patchwork-Id: 680839 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 056DDC7EE26 for ; Wed, 10 May 2023 16:04:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230014AbjEJQEk (ORCPT ); Wed, 10 May 2023 12:04:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229617AbjEJQEg (ORCPT ); Wed, 10 May 2023 12:04:36 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B5A4728A; Wed, 10 May 2023 09:04:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Content-Type:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=jfWx+0ys4mZjxClgqZp/Lr7IqJWa58C+dJ/FHK6DvTU=; t=1683734675; x=1684944275; b=alGQT65LiTCEJS6qK8FOkRkVJhCoLaCzguyz0SoTGdqgZCz KgNjEHeoSIvVPnqHOYggW1USsffJwqsg9j/DaC6PT8dA1HkgyrwaF+c2kXFQ3S51+0nFX5nLVvdDI ALViarWHhkEFC9nz9FMJa/DCkmfC8gQC94k+53gPC4UoTHv+VWl6VSOoFNNXiKEiLfUjYYzYH6juo vv0qIyrzCvBR3+sLMRFC4R6Y2rcCqZCKd3+eRF0THUl0UugIqBQ4dYWobiibAnfYZfRLacaqhuWYd /gtJfaWBlunt4bSqg2plmeJusRc6WJZCfFvCU8Lah/dasV5P/tQp0/jjk/iJJfDA==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1pwmIq-005Uq9-2e; Wed, 10 May 2023 18:04:32 +0200 From: Johannes Berg To: linux-kernel@vger.kernel.org Cc: linux-wireless@vger.kernel.org, Tejun Heo , Lai Jiangshan , Johannes Berg Subject: [RFC PATCH 1/4] workqueue: support pausing ordered workqueues Date: Wed, 10 May 2023 18:04:25 +0200 Message-Id: <20230510175846.85cb30389c22.Ia49f779e11c2814294ea7f8bb29f825fb840be51@changeid> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230510160428.175409-1-johannes@sipsolutions.net> References: <20230510160428.175409-1-johannes@sipsolutions.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org From: Johannes Berg Add some infrastructure to support pausing ordered workqueues, so that no work items are executing nor can execute while the workqueue is paused. This can be used to simplify locking between work structs and other processes (e.g. userspace calls) when the workqueue is paused while other code is running, where we can then more easily avoid issues in code paths needing to cancel works. Signed-off-by: Johannes Berg --- include/linux/workqueue.h | 26 ++++++++++++++++++++++++++ kernel/workqueue.c | 27 ++++++++++++++++++++++++++- 2 files changed, 52 insertions(+), 1 deletion(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index ac551b8ee7d9..5e2413017a89 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -340,6 +340,7 @@ enum { __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */ __WQ_LEGACY = 1 << 18, /* internal: create*_workqueue() */ __WQ_ORDERED_EXPLICIT = 1 << 19, /* internal: alloc_ordered_workqueue() */ + __WQ_PAUSED = 1 << 20, /* internal: workqueue_pause() */ WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */ WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */ @@ -474,6 +475,31 @@ extern void print_worker_info(const char *log_lvl, struct task_struct *task); extern void show_all_workqueues(void); extern void show_one_workqueue(struct workqueue_struct *wq); extern void wq_worker_comm(char *buf, size_t size, struct task_struct *task); +extern void __workqueue_pause_resume(struct workqueue_struct *wq, bool pause); + +/** + * workqueue_pause - pause a workqueue + * @wq: workqueue to pause + * + * Pause (and flush) the given workqueue so it's not executing any + * work structs and won't until workqueue_resume() is called. + */ +static inline void workqueue_pause(struct workqueue_struct *wq) +{ + __workqueue_pause_resume(wq, true); +} + +/** + * workqueue_resume - resume a paused workqueue + * @wq: workqueue to resume + * + * Resume the given workqueue that was paused previously to + * make it run work structs again. + */ +static inline void workqueue_resume(struct workqueue_struct *wq) +{ + __workqueue_pause_resume(wq, false); +} /** * queue_work - queue work on a workqueue diff --git a/kernel/workqueue.c b/kernel/workqueue.c index b8b541caed48..418d99ff8325 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3863,10 +3863,16 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) struct workqueue_struct *wq = pwq->wq; bool freezable = wq->flags & WQ_FREEZABLE; unsigned long flags; + int new_max_active; - /* for @wq->saved_max_active */ + /* for @wq->saved_max_active and @wq->flags */ lockdep_assert_held(&wq->mutex); + if (wq->flags & __WQ_PAUSED) + new_max_active = 0; + else + new_max_active = wq->saved_max_active; + /* fast exit for non-freezable wqs */ if (!freezable && pwq->max_active == wq->saved_max_active) return; @@ -4642,6 +4648,25 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) } EXPORT_SYMBOL_GPL(workqueue_set_max_active); +void __workqueue_pause_resume(struct workqueue_struct *wq, bool pause) +{ + struct pool_workqueue *pwq; + + mutex_lock(&wq->mutex); + if (pause) + wq->flags |= __WQ_PAUSED; + else + wq->flags &= ~__WQ_PAUSED; + + for_each_pwq(pwq, wq) + pwq_adjust_max_active(pwq); + mutex_unlock(&wq->mutex); + + if (pause) + flush_workqueue(wq); +} +EXPORT_SYMBOL_GPL(__workqueue_pause_resume); + /** * current_work - retrieve %current task's work struct *