From mboxrd@z Thu Jan 1 00:00:00 1970 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 138E2C61DB3 for ; Tue, 10 Jan 2023 20:31:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234080AbjAJUbJ (ORCPT ); Tue, 10 Jan 2023 15:31:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234969AbjAJUaY (ORCPT ); Tue, 10 Jan 2023 15:30:24 -0500 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7851633A9 for ; Tue, 10 Jan 2023 12:28:47 -0800 (PST) Received: by mail-pj1-x102c.google.com with SMTP id c8-20020a17090a4d0800b00225c3614161so17699861pjg.5 for ; Tue, 10 Jan 2023 12:28:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=WNez16VMF4rRmKYhCe0O3ABHc5tdrND3Cm+xmlv4IIQ=; b=VDtEnRD0IULnX2C+hz7ue9+Ox87DOT+65LNmd6Y8TrDOritXAKvpw5sE/xe22MNPgp 6fycVwPIDqgFeyrCKVBf9XMngexY72yWSKnWg/uznGFCiCahyGaZNBBgFq4g+oloYZBY HcKK5Rm9+BJEOXjeTHagp6I1GQZmyDZZw+HgJTxzmqEatwzESgqMaWS/vDSTBwN5tlMP ZF7ura2oe1p7EO8S3bl+NSPEiSLldLpC/Mr5mXFUCqUk3d8eA3H1zvpvSiNz9wE767w1 jzEBso/x4g5vvrBfa2bqya+2hG47870jxcjGjiNH7NZWJhwfLckBhg7eOeOpzb7C4iMO erTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=WNez16VMF4rRmKYhCe0O3ABHc5tdrND3Cm+xmlv4IIQ=; b=C0dbAYGc66K6h2uCPFnPZUyUDuP8MP9M6wQpG/9xE8Wj60BjIyLLhlVZZJVUwYw32W N2b6XqcI0xHl3CYC5ioFe7SO6nDWVwwAY+xoWVdPJRIugG6j/9YwpvRxqsS7dlwM0HXJ kVZyjcREs+GbTg05bk5dxGq8nPq1rJL4cbTfD8rzb0r2K/C52wYvwPqdwHzWcTEduaLL KNnG0+5NgomnPiGhyU5wL+jJgEoboP4Wid0wqw7blBtPxOcavRrxsN/GxwAOsyDpDfQX ag54aI5LS9LYTvtas+SN3M5oC+/PywtWpsE9ug//6d3AOMMpNJOxtIqpFcmRDedXAoHm n2Kg== X-Gm-Message-State: AFqh2kq5IGe0czgFnkamqGK2tCIDm79QfjR6R4QUr9MWAu4ZIxoAjiMV aXHRg6BmbUDBg4BXCmp7dSo= X-Google-Smtp-Source: AMrXdXs5B83oTFUdyufH1m6gzfZsgR/0a2/gzotO5bt9J7aYOdGXU4G0YeySaAOMGhg/T+mqUwdRWQ== X-Received: by 2002:a05:6a20:c78d:b0:a3:878d:c126 with SMTP id hk13-20020a056a20c78d00b000a3878dc126mr89685965pzb.42.1673382523621; Tue, 10 Jan 2023 12:28:43 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id n5-20020a634005000000b004a737a6e62fsm6989361pga.14.2023.01.10.12.28.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Jan 2023 12:28:43 -0800 (PST) Sender: Tejun Heo Date: Tue, 10 Jan 2023 10:28:41 -1000 From: Tejun Heo To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, Lai Jiangshan , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: Re: [PATCH v7 4/4] workqueue: Unbind kworkers before sending them to exit() Message-ID: References: <20230109133316.4026472-1-vschneid@redhat.com> <20230109133316.4026472-5-vschneid@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230109133316.4026472-5-vschneid@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, The series generally looks good to me. Just one thing. On Mon, Jan 09, 2023 at 01:33:16PM +0000, Valentin Schneider wrote: > @@ -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); The original pattern was a bit weird to begin with and this makes it quite worse. Let's do something more straight forward like: while (true) { rcuwait_wait_event(&manager_wait, !(pool->flags & POOL_MANAGER_ACTIVE), TASK_UNINTERRUPTIBLE); mutex_lock(&wq_pool_attach_mutex); raw_spin_lock_irq(&pool->lock); if (!(pool->flags & POOL_MANAGER_ACTIVE)) { pool->flags |= POOL_MANAGER_ACTIVE; break; } raw_spin_unlock_irq(&pool->lock); mutex_unlock(&wq_pool_attach_mutex); } Thanks. -- tejun