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=-2.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 F02ADC43441 for ; Wed, 14 Nov 2018 02:35:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A53E1223C8 for ; Wed, 14 Nov 2018 02:35:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="2MuA1Xh9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A53E1223C8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727065AbeKNMgw (ORCPT ); Wed, 14 Nov 2018 07:36:52 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:36907 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726496AbeKNMgw (ORCPT ); Wed, 14 Nov 2018 07:36:52 -0500 Received: by mail-pg1-f196.google.com with SMTP id 80so6638768pge.4 for ; Tue, 13 Nov 2018 18:35:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=s07AIUNZ/+ef0gRDKSExt5oHPz538foRirX1HNC6QHY=; b=2MuA1Xh9kkSjnLEUJn+l/tCP6dhOKPFKxUr2fqmVFFtFgvglP4+pXqh+8UL7cSRXy1 V88SFTc5QQAr/EZYmMw9z78dRkgJttXiVdPPBBnfsRZGaBKOZS+K+alHO0nxpfp3COIr 0uKOQTiqyObe9vpQPgkeUAiP/kpI7EvBCkmm96Y3mTKKS3ru92l/SZHVmVPTtOBuLiP7 bLOa6dA/vpUZIiv68I6RgVG2Z10pe779U6vdF1TrV/pF73o/+F22tXANJo+uyAGNzbMM kEVOFhKRwD/06jz64BIN1d6X2iMrAUKtaMZyOAlgOLLj1JG4Ns9RUe+2ubCh93PaFChQ VjMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=s07AIUNZ/+ef0gRDKSExt5oHPz538foRirX1HNC6QHY=; b=dZuCv3HJ/xPLsO0/k3QzZL2I6PsLsfCRUt/lZKfugfCrqtowVOmFpbT3TYSxyFQx4U AR27zIG2kJBSA0hwj9HSRXJy28Ie3zIChdXrvN0WuWh4NfLvW7UlNpDiLCoCbN1D3EWA XazlwY4jqFbnl41HQTAQC1RPN4Y1O+rvpfPvB1NAFaNqYIC+6JmnpEidHi6NULfrJebz KVaJh2Nh70DxbjWzjdbLwKEpplfHOuvub229xhWd1Lk52cn79kOw0RafSusNcyYj2Q++ QXNVV6aQ6mQfxqOZSDfazuEb2HoHmDR1f0CWJ8Hb5luRRVqMj5WzSq06YCxRTrtybrkT WyCg== X-Gm-Message-State: AGRZ1gKJ2nGbqfLvwOX8BacLSfMJYl4SyjKMpp/ZLJt8RLs4mPAMKK36 c7fS9vJwUMsHjFXP8khY2TTNnWbaIn4= X-Google-Smtp-Source: AJdET5faDcEKZeFKD1O4kUz7soKXV+7wub5SZ1xBgBrOHqvRtoV8S5gQqGVF3fmhSTcECRo7i/Bpgw== X-Received: by 2002:a62:65c3:: with SMTP id z186-v6mr114264pfb.206.1542162943219; Tue, 13 Nov 2018 18:35:43 -0800 (PST) Received: from ?IPv6:2620:10d:c081:1134::122f? ([2620:10d:c090:180::1:2c26]) by smtp.gmail.com with ESMTPSA id w2-v6sm25669292pfn.89.2018.11.13.18.35.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Nov 2018 18:35:42 -0800 (PST) Subject: Re: [PATCH 05/11] block: avoid ordered task state change for polled IO To: "jianchao.wang" , linux-block@vger.kernel.org References: <20181113154233.15256-1-axboe@kernel.dk> <20181113154233.15256-6-axboe@kernel.dk> From: Jens Axboe Message-ID: <7d16853c-dbeb-45bb-3902-faa5aefad9bb@kernel.dk> Date: Tue, 13 Nov 2018 19:35:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 11/13/18 7:29 PM, jianchao.wang wrote: > Hi Jens > > On 11/13/18 11:42 PM, Jens Axboe wrote: >> @@ -181,6 +181,7 @@ static void blkdev_bio_end_io_simple(struct bio *bio) >> struct task_struct *waiter = bio->bi_private; >> >> WRITE_ONCE(bio->bi_private, NULL); >> + smp_wmb(); >> wake_up_process(waiter); >> } > > > The wake up path has contained a full memory barrier with the raw_spin_lock > and following smp_mb__after_spinlock > > Please refer to: > > wake_up_process > -> try_to_wake_up > > raw_spin_lock_irqsave(&p->pi_lock, flags); > smp_mb__after_spinlock(); > > So the smp_wmb here is not necessary. And I guess we don't need it for the next patch either, since the path that doesn't take wake_up_process() is local. I'll update them (again), thanks! -- Jens Axboe