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=-0.9 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 22B7BC433F5 for ; Mon, 27 Aug 2018 03:52:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B969821722 for ; Mon, 27 Aug 2018 03:52:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="5IrEddDT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B969821722 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 S1726918AbeH0Hgp (ORCPT ); Mon, 27 Aug 2018 03:36:45 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:56768 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725878AbeH0Hgp (ORCPT ); Mon, 27 Aug 2018 03:36:45 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w7R3ncBP158849; Mon, 27 Aug 2018 03:51:47 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=Dy/zir8dpOcjvly0sDcVFFO8kFVllXs2S8pbbSXadps=; b=5IrEddDT1YeKgjuDqAW/WeFx4Lk3ZCr7kbJsqKvlj2TlhaGYXdT7KI2lCCutrDCjl/xD h2RArok6Sf+WFmeDVSFBzjinN8MzAzdtSBw2n1ANQ+BRBpvc7KpfaPqHlil+IYZOdt+N dJ9vPjbV37H51rQypf+jPheiN1nKOszwmUv0lF/SJ+aG3AknMl31dLdVmYnbODhRLoRZ 2tFDDqd6KBdvIffysoW1mbRWXuQVXFVaUAUrGd3YjQ/hwMhkk7vUZYBqhbB7vA4yrZ26 uvEhb2kJQy1+44V31IlPloWsGGgyUR2kXqe7K5eG4r+SnSgmq3AppIWB8cUENwOeOw85 Rw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by aserp2120.oracle.com with ESMTP id 2m2y2p3f8f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 27 Aug 2018 03:51:47 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w7R3pkap006720 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 27 Aug 2018 03:51:46 GMT Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w7R3pjta026694; Mon, 27 Aug 2018 03:51:46 GMT Received: from [10.182.70.180] (/10.182.70.180) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sun, 26 Aug 2018 20:51:45 -0700 Subject: Re: [PATCH] blk-wbt: get back the missed wakeup from __wbt_done To: Jens Axboe , Anchal Agarwal Cc: fllinden@amazon.com, "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <1535029718-17259-1-git-send-email-jianchao.w.wang@oracle.com> <20180823210144.GB5624@kaos-source-ops-60001.pdx1.amazon.com> <3eaa20ce-0599-c405-d979-87d91ea331d2@kernel.dk> <20180824181223.GA9049@kaos-source-ops-60001.pdx1.amazon.com> <677c8648-63fd-601c-b906-40a8502f9782@kernel.dk> <20180824203305.GA4690@kaos-source-ops-60001.pdx1.amazon.com> <2fecf2f2-f00b-f6ba-710a-54ceaacfedbb@kernel.dk> From: "jianchao.wang" Message-ID: <00445460-d826-4d85-c5f4-fa565892da01@oracle.com> Date: Mon, 27 Aug 2018 11:52:26 +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: <2fecf2f2-f00b-f6ba-710a-54ceaacfedbb@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=8997 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=917 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808270041 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jens On 08/25/2018 11:41 PM, Jens Axboe wrote: > do { > - set_current_state(TASK_UNINTERRUPTIBLE); > + if (test_bit(0, &data.flags)) > + break; > > - if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw))) > + WARN_ON_ONCE(list_empty(&data.wq.entry)); > + > + if (!has_sleeper && > + rq_wait_inc_below(rqw, get_limit(rwb, rw))) { > + finish_wait(&rqw->wait, &data.wq); > + > + /* > + * We raced with wbt_wake_function() getting a token, > + * which means we now have two. Put ours and wake > + * anyone else potentially waiting for one. > + */ > + if (test_bit(0, &data.flags)) > + wbt_rqw_done(rwb, rqw, wb_acct); > break; Just use 'bool' variable should be OK After finish_wait, no one could race with us here. > + } > > if (lock) { > spin_unlock_irq(lock); > @@ -511,11 +569,11 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct, > spin_lock_irq(lock); > } else > io_schedule(); > + > has_sleeper = false; > } while (1); I cannot get the point of "since we can't rely on just being woken from the ->func handler we set". Do you mean there could be someone else could wake up this task ? Thanks Jianchao