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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 DBDBFC43441 for ; Thu, 29 Nov 2018 17:02:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 976952145D for ; Thu, 29 Nov 2018 17:02:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 976952145D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1730322AbeK3EIY (ORCPT ); Thu, 29 Nov 2018 23:08:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55242 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729818AbeK3EIX (ORCPT ); Thu, 29 Nov 2018 23:08:23 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E95272D808; Thu, 29 Nov 2018 17:02:20 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-8.bos.redhat.com [10.18.17.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id AC51161530; Thu, 29 Nov 2018 17:02:19 +0000 (UTC) Subject: Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the reader waiter to nil To: Peter Zijlstra Cc: Yongji Xie , mingo@redhat.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, xieyongji@baidu.com, zhangyu31@baidu.com, liuqi16@baidu.com, yuanlinsi01@baidu.com, nixun@baidu.com, lilin24@baidu.com, Davidlohr Bueso References: <1543495830-2644-1-git-send-email-xieyongji@baidu.com> <20181129131232.GN2131@hirez.programming.kicks-ass.net> <5598cd71-c3c8-d6ef-eb30-777cf901a2ef@redhat.com> <20181129160627.GU2131@hirez.programming.kicks-ass.net> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFgsZGsBEAC3l/RVYISY3M0SznCZOv8aWc/bsAgif1H8h0WPDrHnwt1jfFTB26EzhRea XQKAJiZbjnTotxXq1JVaWxJcNJL7crruYeFdv7WUJqJzFgHnNM/upZuGsDIJHyqBHWK5X9ZO jRyfqV/i3Ll7VIZobcRLbTfEJgyLTAHn2Ipcpt8mRg2cck2sC9+RMi45Epweu7pKjfrF8JUY r71uif2ThpN8vGpn+FKbERFt4hW2dV/3awVckxxHXNrQYIB3I/G6mUdEZ9yrVrAfLw5M3fVU CRnC6fbroC6/ztD40lyTQWbCqGERVEwHFYYoxrcGa8AzMXN9CN7bleHmKZrGxDFWbg4877zX 0YaLRypme4K0ULbnNVRQcSZ9UalTvAzjpyWnlnXCLnFjzhV7qsjozloLTkZjyHimSc3yllH7 VvP/lGHnqUk7xDymgRHNNn0wWPuOpR97J/r7V1mSMZlni/FVTQTRu87aQRYu3nKhcNJ47TGY evz/U0ltaZEU41t7WGBnC7RlxYtdXziEn5fC8b1JfqiP0OJVQfdIMVIbEw1turVouTovUA39 Qqa6Pd1oYTw+Bdm1tkx7di73qB3x4pJoC8ZRfEmPqSpmu42sijWSBUgYJwsziTW2SBi4hRjU h/Tm0NuU1/R1bgv/EzoXjgOM4ZlSu6Pv7ICpELdWSrvkXJIuIwARAQABzR9Mb25nbWFuIExv bmcgPGxsb25nQHJlZGhhdC5jb20+wsF/BBMBAgApBQJYLGRrAhsjBQkJZgGABwsJCAcDAgEG FQgCCQoLBBYCAwECHgECF4AACgkQbjBXZE7vHeYwBA//ZYxi4I/4KVrqc6oodVfwPnOVxvyY oKZGPXZXAa3swtPGmRFc8kGyIMZpVTqGJYGD9ZDezxpWIkVQDnKM9zw/qGarUVKzElGHcuFN ddtwX64yxDhA+3Og8MTy8+8ZucM4oNsbM9Dx171bFnHjWSka8o6qhK5siBAf9WXcPNogUk4S fMNYKxexcUayv750GK5E8RouG0DrjtIMYVJwu+p3X1bRHHDoieVfE1i380YydPd7mXa7FrRl 7unTlrxUyJSiBc83HgKCdFC8+ggmRVisbs+1clMsK++ehz08dmGlbQD8Fv2VK5KR2+QXYLU0 rRQjXk/gJ8wcMasuUcywnj8dqqO3kIS1EfshrfR/xCNSREcv2fwHvfJjprpoE9tiL1qP7Jrq 4tUYazErOEQJcE8Qm3fioh40w8YrGGYEGNA4do/jaHXm1iB9rShXE2jnmy3ttdAh3M8W2OMK 4B/Rlr+Awr2NlVdvEF7iL70kO+aZeOu20Lq6mx4Kvq/WyjZg8g+vYGCExZ7sd8xpncBSl7b3 99AIyT55HaJjrs5F3Rl8dAklaDyzXviwcxs+gSYvRCr6AMzevmfWbAILN9i1ZkfbnqVdpaag QmWlmPuKzqKhJP+OMYSgYnpd/vu5FBbc+eXpuhydKqtUVOWjtp5hAERNnSpD87i1TilshFQm TFxHDzbOwU0EWCxkawEQALAcdzzKsZbcdSi1kgjfce9AMjyxkkZxcGc6Rhwvt78d66qIFK9D Y9wfcZBpuFY/AcKEqjTo4FZ5LCa7/dXNwOXOdB1Jfp54OFUqiYUJFymFKInHQYlmoES9EJEU yy+2ipzy5yGbLh3ZqAXyZCTmUKBU7oz/waN7ynEP0S0DqdWgJnpEiFjFN4/ovf9uveUnjzB6 lzd0BDckLU4dL7aqe2ROIHyG3zaBMuPo66pN3njEr7IcyAL6aK/IyRrwLXoxLMQW7YQmFPSw drATP3WO0x8UGaXlGMVcaeUBMJlqTyN4Swr2BbqBcEGAMPjFCm6MjAPv68h5hEoB9zvIg+fq M1/Gs4D8H8kUjOEOYtmVQ5RZQschPJle95BzNwE3Y48ZH5zewgU7ByVJKSgJ9HDhwX8Ryuia 79r86qZeFjXOUXZjjWdFDKl5vaiRbNWCpuSG1R1Tm8o/rd2NZ6l8LgcK9UcpWorrPknbE/pm MUeZ2d3ss5G5Vbb0bYVFRtYQiCCfHAQHO6uNtA9IztkuMpMRQDUiDoApHwYUY5Dqasu4ZDJk bZ8lC6qc2NXauOWMDw43z9He7k6LnYm/evcD+0+YebxNsorEiWDgIW8Q/E+h6RMS9kW3Rv1N qd2nFfiC8+p9I/KLcbV33tMhF1+dOgyiL4bcYeR351pnyXBPA66ldNWvABEBAAHCwWUEGAEC AA8FAlgsZGsCGwwFCQlmAYAACgkQbjBXZE7vHeYxSQ/+PnnPrOkKHDHQew8Pq9w2RAOO8gMg 9Ty4L54CsTf21Mqc6GXj6LN3WbQta7CVA0bKeq0+WnmsZ9jkTNh8lJp0/RnZkSUsDT9Tza9r GB0svZnBJMFJgSMfmwa3cBttCh+vqDV3ZIVSG54nPmGfUQMFPlDHccjWIvTvyY3a9SLeamaR jOGye8MQAlAD40fTWK2no6L1b8abGtziTkNh68zfu3wjQkXk4kA4zHroE61PpS3oMD4AyI9L 7A4Zv0Cvs2MhYQ4Qbbmafr+NOhzuunm5CoaRi+762+c508TqgRqH8W1htZCzab0pXHRfywtv 0P+BMT7vN2uMBdhr8c0b/hoGqBTenOmFt71tAyyGcPgI3f7DUxy+cv3GzenWjrvf3uFpxYx4 yFQkUcu06wa61nCdxXU/BWFItryAGGdh2fFXnIYP8NZfdA+zmpymJXDQeMsAEHS0BLTVQ3+M 7W5Ak8p9V+bFMtteBgoM23bskH6mgOAw6Cj/USW4cAJ8b++9zE0/4Bv4iaY5bcsL+h7TqQBH Lk1eByJeVooUa/mqa2UdVJalc8B9NrAnLiyRsg72Nurwzvknv7anSgIkL+doXDaG21DgCYTD wGA5uquIgb8p3/ENgYpDPrsZ72CxVC2NEJjJwwnRBStjJOGQX4lV1uhN1XsZjBbRHdKF2W9g weim8xU= Organization: Red Hat Message-ID: <8cc45695-b325-a219-8b46-d5da6ddfdd63@redhat.com> Date: Thu, 29 Nov 2018 12:02:19 -0500 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: <20181129160627.GU2131@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: base64 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 29 Nov 2018 17:02:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org T24gMTEvMjkvMjAxOCAxMTowNiBBTSwgUGV0ZXIgWmlqbHN0cmEgd3JvdGU6Cj4gT24gVGh1 LCBOb3YgMjksIDIwMTggYXQgMTA6MjE6NThBTSAtMDUwMCwgV2FpbWFuIExvbmcgd3JvdGU6 Cj4KPj4+PiBkaWZmIC0tZ2l0IGEva2VybmVsL2xvY2tpbmcvcndzZW0teGFkZC5jIGIva2Vy bmVsL2xvY2tpbmcvcndzZW0teGFkZC5jCj4+Pj4gaW5kZXggMDliMTgwMC4uNTBkOWFmNiAx MDA2NDQKPj4+PiAtLS0gYS9rZXJuZWwvbG9ja2luZy9yd3NlbS14YWRkLmMKPj4+PiArKysg Yi9rZXJuZWwvbG9ja2luZy9yd3NlbS14YWRkLmMKPj4+PiBAQCAtMTk4LDE1ICsxOTgsMjIg QEAgc3RhdGljIHZvaWQgX19yd3NlbV9tYXJrX3dha2Uoc3RydWN0IHJ3X3NlbWFwaG9yZSAq c2VtLAo+Pj4+ICAJCXdva2VuKys7Cj4+Pj4gIAkJdHNrID0gd2FpdGVyLT50YXNrOwo+Pj4+ ICAKPj4+PiAtCQl3YWtlX3FfYWRkKHdha2VfcSwgdHNrKTsKPj4+PiArCQlnZXRfdGFza19z dHJ1Y3QodHNrKTsKPj4+PiAgCQlsaXN0X2RlbCgmd2FpdGVyLT5saXN0KTsKPj4+PiAgCQkv Kgo+Pj4+IC0JCSAqIEVuc3VyZSB0aGF0IHRoZSBsYXN0IG9wZXJhdGlvbiBpcyBzZXR0aW5n IHRoZSByZWFkZXIKPj4+PiArCQkgKiBFbnN1cmUgY2FsbGluZyBnZXRfdGFza19zdHJ1Y3Qo KSBiZWZvcmUgc2V0dGluZyB0aGUgcmVhZGVyCj4+Pj4gIAkJICogd2FpdGVyIHRvIG5pbCBz dWNoIHRoYXQgcndzZW1fZG93bl9yZWFkX2ZhaWxlZCgpIGNhbm5vdAo+Pj4+ICAJCSAqIHJh Y2Ugd2l0aCBkb19leGl0KCkgYnkgYWx3YXlzIGhvbGRpbmcgYSByZWZlcmVuY2UgY291bnQK Pj4+PiAgCQkgKiB0byB0aGUgdGFzayB0byB3YWtldXAuCj4+Pj4gIAkJICovCj4+Pj4gIAkJ c21wX3N0b3JlX3JlbGVhc2UoJndhaXRlci0+dGFzaywgTlVMTCk7Cj4+Pj4gKwkJLyoKPj4+ PiArCQkgKiBFbnN1cmUgaXNzdWluZyB0aGUgd2FrZXVwIChlaXRoZXIgYnkgdXMgb3Igc29t ZW9uZSBlbHNlKQo+Pj4+ICsJCSAqIGFmdGVyIHNldHRpbmcgdGhlIHJlYWRlciB3YWl0ZXIg dG8gbmlsLgo+Pj4+ICsJCSAqLwo+Pj4+ICsJCXdha2VfcV9hZGQod2FrZV9xLCB0c2spOwo+ Pj4+ICsJCS8qIHdha2VfcV9hZGQoKSBhbHJlYWR5IHRha2UgdGhlIHRhc2sgcmVmICovCj4+ Pj4gKwkJcHV0X3Rhc2tfc3RydWN0KHRzayk7Cj4+Pj4gIAl9Cj4+Pj4gIAo+Pj4+ICAJYWRq dXN0bWVudCA9IHdva2VuICogUldTRU1fQUNUSVZFX1JFQURfQklBUyAtIGFkanVzdG1lbnQ7 Cj4+IEkgZG91YnQgcHV0dGluZyB3YWtlX3FfYWRkKCkgYWZ0ZXIgY2xlYXJpbmcgd2FpdGVy LT50YXNrIGNhbiByZWFsbHkgZml4Cj4gV2h5OyBhdCB0aGF0IHBvaW50IHdlIGtub3cgdGhl IHdha2V1cCB3aWxsIGhhcHBlbiBhZnRlciwgd2hpY2ggaXMgYWxsIHdlCj4gcmVxdWlyZS4K Pgo+CgpUaHJlYWQgMcKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoCBUaHJlYWQgMsKgwqDCoMKgwqAgVGhyZWFkIDMK CsKgwqDCoCByd3NlbV9kb3duX3JlYWRfZmFpbGVkKCkKwqByYXdfc3Bpbl9sb2NrX2lycSgm c2VtLT53YWl0X2xvY2spOwrCoGxpc3RfYWRkX3RhaWwoJndhaXRlci5saXN0LCAmd2FpdF9s aXN0KTsKwqByYXdfc3Bpbl91bmxvY2tfaXJxKCZzZW0tPndhaXRfbG9jayk7CsKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgIF9fcndz ZW1fbWFya193YWtlKCk7CsKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqAgd2FrZV9xX2FkZCgpOwrCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgIHdha2VfdXBfcSgpOwrCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgIHdhaXRlci0+dGFzayA9Ck5VTEw7IC0tKwrC oHdoaWxlICh0cnVlKQp7wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqAgfArCoApzZXRfY3VycmVudF9z dGF0ZShUQVNLX1VOSU5URVJSVVBUSUJMRSk7wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqAKfArCoCBp ZiAoIXdhaXRlci50YXNrKSAvLwpmYWxzZcKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoCB8CsKgwqDCoMKgwqAKYnJlYWs7wqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqAgfArCoApzY2hlZHVsZSgpO8KgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoAp8 CsKgfcKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqAKPC0tLS0tKwrCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDC oMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoCB3YWtl X3VwX3EoJndha2VfcSk7CgpPSywgSSBnb3QgY29uZnVzZWQgYnkgdGhlIHRocmVhZCByYWNp bmcgY2hhcnQgc2hvd24gaW4gdGhlIHBhdGNoLiBJdAp3aWxsIGJlIGNsZWFyZXIgaWYgdGhl IGNsZWFyaW5nIG9mIHdhaXRlci0+dGFzayBpcyBtb3ZlZCBkb3duIGFzIHNob3duLgpPdGhl cndpc2UsIG1vdmluZyB0aGUgY2xlYXJpbmcgb2Ygd2FpdGVyLT50YXNrIGJlZm9yZSB3YWtl X3FfYWRkKCkgd29uJ3QKbWFrZSBhIGRpZmZlcmVuY2UuIFNvIHRoZSBwYXRjaCBjYW4gYmUg YSBwb3NzaWJsZSBmaXguCgpTdGlsbCB3ZSBhcmUgdGFsa2luZyBhYm91dCAzIHRocmVhZHMg cmFjaW5nIHdpdGggZWFjaCBvdGhlci4gVGhlCmNsZWFyaW5nIG9mIHdha2VfcS5uZXh0IGlu IHdha2VfdXBfcSgpIGlzIG5vdCBhdG9taWMgYW5kIGl0IGlzIGhhcmQgdG8KcHJlZGljdCB0 aGUgcmFjaW5nIHJlc3VsdCBvZiB0aGUgY29uY3VycmVudCB3YWtlX3Egb3BlcmF0aW9ucyBi ZXR3ZWVuCnRocmVhZHMgMiBhbmQgMy4gVGhlIGVzc2VuY2Ugb2YgbXkgdGVudGF0aXZlIHBh dGNoIGlzIHRvIHByZXZlbnQgdGhlCmNvbmN1cnJlbnQgd2FrZV9xIG9wZXJhdGlvbnMgaW4g dGhlIGZpcnN0IHBsYWNlLgoKQ2hlZXJzLApMb25nbWFuCgoKClRoZSBzZWNvbmQgd2FrZV9x X2FkZCgpIGFib3ZlIHdpbGwgZmFpbCB0byBhZGQgdGhlIHRhc2sgdG8gdGhlIHNlY29uZAp3 YWtlX3EgYmVjYXVzZSBpdCBpcyBzdGlsbCBpbiB0aGUgZmlyc3Qgd2FrZV9xLiBTbyB0aGUg c2Vjb25kCndha2VfdXBfcSgpIHdpbGwgbm90IHdha2UgdXAgdGhlIHRhc2sgYmVjYXVzZSBp dCBpcyBub3QgaW4gaXRzIHdha2VfcS4KCkNoZWVycywKTG9uZ21hbgoKCg==