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 D3552C433EF for ; Tue, 15 Feb 2022 12:49:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236587AbiBOMta (ORCPT ); Tue, 15 Feb 2022 07:49:30 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:51612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbiBOMt2 (ORCPT ); Tue, 15 Feb 2022 07:49:28 -0500 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B228D28E27; Tue, 15 Feb 2022 04:49:18 -0800 (PST) Received: from fsav117.sakura.ne.jp (fsav117.sakura.ne.jp [27.133.134.244]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 21FCn2cr076466; Tue, 15 Feb 2022 21:49:02 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav117.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp); Tue, 15 Feb 2022 21:49:02 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 21FCn233076461 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Tue, 15 Feb 2022 21:49:02 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: Date: Tue, 15 Feb 2022 21:48:58 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.0 Subject: Re: [syzbot] possible deadlock in worker_thread Content-Language: en-US To: Haakon Bugge Cc: Tejun Heo , Bart Van Assche , syzbot , Jason Gunthorpe , LKML , OFED mailing list , "syzkaller-bugs@googlegroups.com" , Lai Jiangshan References: <0000000000005975a605d7aef05e@google.com> <8ea57ddf-a09c-43f2-4285-4dfb908ad967@acm.org> <71d6f14e-46af-cc5a-bc70-af1cdc6de8d5@acm.org> <309c86b7-2a4c-1332-585f-7bcd59cfd762@I-love.SAKURA.ne.jp> <2959649d-cfbc-bdf2-02ac-053b8e7af030@I-love.SAKURA.ne.jp> <8ebd003c-f748-69b4-3a4f-fb80a3f39d36@I-love.SAKURA.ne.jp> <76616D2F-14F2-4D83-9DB4-576FB2ACB72C@oracle.com> From: Tetsuo Handa In-Reply-To: <76616D2F-14F2-4D83-9DB4-576FB2ACB72C@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/02/15 19:43, Haakon Bugge wrote: >> @@ -6070,6 +6087,13 @@ void __init workqueue_init_early(void) >> !system_unbound_wq || !system_freezable_wq || >> !system_power_efficient_wq || >> !system_freezable_power_efficient_wq); >> + system_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_highpri_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_long_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_unbound_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_freezable_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_power_efficient_wq->flags |= __WQ_SYSTEM_WIDE; >> + system_freezable_power_efficient_wq->flags |= __WQ_SYSTEM_WIDE; > > Better to OR this in, in the alloc_workqueue() call? Perceive the notion of an opaque object? > I do not want to do like - system_wq = alloc_workqueue("events", 0, 0); + system_wq = alloc_workqueue("events", __WQ_SYSTEM_WIDE, 0); because the intent of this change is to ask developers to create their own WQs. If I pass __WQ_SYSTEM_WIDE to alloc_workqueue(), developers might by error create like srp_tl_err_wq = alloc_workqueue("srp_tl_err_wq", __WQ_SYSTEM_WIDE, 0); because of system_wq = alloc_workqueue("events", __WQ_SYSTEM_WIDE, 0); line. The __WQ_SYSTEM_WIDE is absolutely meant to be applied to only 'system_wq', 'system_highpri_wq', 'system_long_wq', 'system_unbound_wq', 'system_freezable_wq', 'system_power_efficient_wq' and 'system_freezable_power_efficient_wq' WQs, in order to avoid calling flush_workqueue() on these system-wide WQs. I wish I could define __WQ_SYSTEM_WIDE inside kernel/workqueue_internal.h, but it seems that kernel/workqueue_internal.h does not define internal flags.