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 4569EC282DA for ; Fri, 19 Apr 2019 19:22:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0CFBE20693 for ; Fri, 19 Apr 2019 19:22:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727571AbfDSTWv (ORCPT ); Fri, 19 Apr 2019 15:22:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37856 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725961AbfDSTWs (ORCPT ); Fri, 19 Apr 2019 15:22:48 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E1F83883BA; Fri, 19 Apr 2019 16:56:25 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-19.bos.redhat.com [10.18.17.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id ABAB51001E95; Fri, 19 Apr 2019 16:56:22 +0000 (UTC) Subject: Re: [PATCH v5 00/18] locking/rwsem: Rwsem rearchitecture part 2 From: Waiman Long To: Ingo Molnar Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org, Davidlohr Bueso , Linus Torvalds , Tim Chen , huang ying References: <20190418234628.3675-1-longman@redhat.com> <8f1adff7-3bd4-7d35-1a0d-698662bfa2b8@redhat.com> <20190419075055.GA6795@gmail.com> <20190419124944.GA44010@gmail.com> 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: Date: Fri, 19 Apr 2019 12:56:22 -0400 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: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 19 Apr 2019 16:56:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/2019 11:00 AM, Waiman Long wrote: > On 04/19/2019 08:49 AM, Ingo Molnar wrote: >> * Ingo Molnar wrote: >> >>> * Waiman Long wrote: >>> >>>> On 04/18/2019 07:46 PM, Waiman Long wrote: >>>>> v5: >>>>> - Drop v4 patch 1 as it is merged into tip's locking/core branch. >>>>> - Integrate the 2 followup patches into the series. The first >>>>> follow-up patch is broken into 2 pieces. The first piece comes in >>>>> before the "Enable readers spinning on writer" and the 2nd piece >>>>> is merged into the "Enable time-based spinning on reader-owned >>>>> rwsem" patch. The 2nd followup patch is added after that. >>>>> - Add a new patch to make all wake_up_q() calls after dropping >>>>> wait_lock as suggested by PeterZ. >>>>> - Incorporate numerouos suggestions by PeterZ and Davidlohr. >>>> This patchset is still being reviewed by Peter . The purpose of this >>>> series is mainly to sync up the version that Peter has and the ones that >>>> I am working on incorporating his feedback. Further changes may still be >>>> needed. >>>> >>>> I run an overall performance test on this new patchset and present the >>>> data in this cover letter. However, I haven't run performance tests for >>>> individual patches. So the performance data listed in some of the >>>> patches may be stale. >>> Just for those who'd like to follow the scope of changes, find below the >>> v4->v5 interdiff. v5 is now included in tip:WIP.locking/core, and also >>> merged into tip:master. (But not propagated towards linux-next yet.) >> Hm, I'm experiencing early boot hangs with v5, on defconfig-ish x86-64 >> kernels: >> >> [ 0.153940] rcu: Hierarchical RCU implementation. >> [ 0.154289] rcu: RCU restricting CPUs from NR_CPUS=128 to nr_cpu_ids=17. >> [ 0.154829] rcu: RCU calculated value of scheduler-enlistment delay is 100 jiffies. >> [ 0.155390] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=17 >> >> >> I bisected it back to the v5 version of this patch: >> >> 2fd5f60fa4c3: locking/rwsem: Merge owner into count on x86-64 >> >> I'm moving -tip back to -v4 meanwhile. >> >> Thanks, >> >> Ingo > Sorry about that. Will look into that problem. > > -Longman > Yes, there is a bug in that patch. The following change should fix it: diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 19d8fbd50d17..857dff330f9b 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -198,9 +198,15 @@  /*   * Task structure pointer compression (64-bit only):   * (owner - PAGE_OFFSET) >> (L1_CACHE_SHIFT - 2) + * + * However, init_task may lie outside of the linearly mapped physical + * to virtual memory range and so has to be handled separately.   */  static inline unsigned long rwsem_owner_count(struct task_struct *owner)  { +       if (unlikely(owner == &init_task)) +               return RWSEM_WRITER_MASK; +         return ((unsigned long)owner - PAGE_OFFSET) >> (L1_CACHE_SHIFT - 2);  } @@ -208,6 +214,9 @@ static inline unsigned long rwsem_count_owner(long count)  {         unsigned long writer = (unsigned long)count & RWSEM_WRITER_MASK; +       if (unlikely(writer == RWSEM_WRITER_MASK)) +               return (unsigned long)&init_task; +         return writer ? (writer << (L1_CACHE_SHIFT - 2)) + PAGE_OFFSET : 0;  }