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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B567C4321D for ; Fri, 24 Aug 2018 02:06:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B80BB2156D for ; Fri, 24 Aug 2018 02:06:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="yTbbcyrM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B80BB2156D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727067AbeHXFiw (ORCPT ); Fri, 24 Aug 2018 01:38:52 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:38958 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725735AbeHXFiw (ORCPT ); Fri, 24 Aug 2018 01:38:52 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w7O1wpiB158389; Fri, 24 Aug 2018 02:06:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=lpvdxCPk8cyrRuEZcpDHHRuWigvm11uos2KRuk3gj2w=; b=yTbbcyrMd+Fz4TKBKJ+YeluAGlTxzMz2wMHwK3Czaufp8yCOKxCR7QhZGLxDRFAJ+yTo wSylXXLfeIfFM9HEaiSQLOkqBeIQbrkTghgYnUCXhM6vWesh10KZ+pDaCZDq1PV2Sti/ +nbdsNmBOMddPGbSHxfbxF9ejTmjzw1wN/yqivztr/6TKy330c+egmTqCkysa9mazr06 MWCQ02ihFdl9HnRgQBJBc76ZoQUpKoViMZxaY1Uqg3dsJf9wHX33vcyD1WOdPNOWFts0 RsQypnpXFG1ldxMAWcXX25c2pf+BEsjPxG8jPYuW3gfnIgsJnZO8nISC2+XX5YKnpmTs Pw== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by userp2130.oracle.com with ESMTP id 2kxavu4nad-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Aug 2018 02:06:25 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w7O26JGI019058 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Aug 2018 02:06:19 GMT Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w7O26IjH014474; Fri, 24 Aug 2018 02:06:19 GMT Received: from [10.182.69.179] (/10.182.69.179) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 23 Aug 2018 19:06:18 -0700 Subject: Re: [PATCH] blk-wbt: get back the missed wakeup from __wbt_done To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <1535029718-17259-1-git-send-email-jianchao.w.wang@oracle.com> <809b2243-7a76-3d8a-5d1b-b6b9d9712f41@kernel.dk> From: "jianchao.wang" Message-ID: Date: Fri, 24 Aug 2018 10:06:56 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <809b2243-7a76-3d8a-5d1b-b6b9d9712f41@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8994 signatures=668707 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808240020 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jens On 08/23/2018 11:42 PM, Jens Axboe wrote: >> - >> - __set_current_state(TASK_RUNNING); >> - remove_wait_queue(&rqw->wait, &wait); >> + wbt_init_wait(&wait, &data); >> + prepare_to_wait_exclusive(&rqw->wait, &wait, >> + TASK_UNINTERRUPTIBLE); >> + if (lock) { >> + spin_unlock_irq(lock); >> + io_schedule(); >> + spin_lock_irq(lock); >> + } else >> + io_schedule(); > Aren't we still missing a get-token attempt after adding to the > waitqueue? For the case where someone frees the token after your initial > check, but before you add yourself to the waitqueue. I used to think about this. However, there is a very tricky scenario here: We will try get the wbt budget in wbt_wake_function. After add a task into the wait queue, wbt_wake_function has been able to be invoked for this task. If we get the wbt budget after prepare_to_wait_exclusive, we may get wbt budget twice. Thanks Jianchao