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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20A84C52D6F for ; Tue, 6 Aug 2024 09:13:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7FF096B007B; Tue, 6 Aug 2024 05:12:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7AF656B0082; Tue, 6 Aug 2024 05:12:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 628956B0083; Tue, 6 Aug 2024 05:12:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 3F3276B007B for ; Tue, 6 Aug 2024 05:12:59 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id AD811A04E2 for ; Tue, 6 Aug 2024 09:12:58 +0000 (UTC) X-FDA: 82421256036.17.43ED258 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 6173620010 for ; Tue, 6 Aug 2024 09:12:56 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=fb3ND33f; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1722935506; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=/lfJgrSWKWbjRxr+WslEUzWg5lU4B6E1b6f6UsWxKzQ=; b=khHgX9xbvVAQhDtXX3/U2D+c/GKV9XcENAB1fMe5mbIjstz4skVWP98LqGbXYkkWFsmbG9 /9uSeqEBhMGlVGBKmE1W9sCkQ57LuUQx0926cw24he0QV/9F6Kn4bXN1pBCTCjUjeuc5LK u49KLP6aHCbw7GFJH2My6UpmW6n3pdE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1722935506; a=rsa-sha256; cv=none; b=aGD+dhiMKvtAq/r54ZOathbRTdwrYF/n7t/SqWQe+DjbTHrazrjyzc5bWmWLnGCYk+sjQ2 lVV09VLySeAtne3zxUBQQcOWcMTcHE3rLBkeIHsYCvBJ7i7CVXgOFHn9LjLcGy1cxOTSDE iCjtt7WGEILBhs0d6e4wBE32jwZnuho= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=fb3ND33f; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722935575; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/lfJgrSWKWbjRxr+WslEUzWg5lU4B6E1b6f6UsWxKzQ=; b=fb3ND33fTC1o8z7AwkzBUV9v2scWQ8YCx1aOZciIeLLwipO1Nu+IOfGbUGx2AG003zHVM/ gvz7qj50qWM9v7FomOzXu88X+6B35va8haTalATMZ0uo54ZwcEp0Hn1HQHb2luPRRzr8tJ CyWk9O43Zi27MX1NG7BIgQttXDFq48M= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-248-g4L8ZjFcPWehmkTsRLIIPQ-1; Tue, 06 Aug 2024 05:12:54 -0400 X-MC-Unique: g4L8ZjFcPWehmkTsRLIIPQ-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4282164fcbcso2985465e9.2 for ; Tue, 06 Aug 2024 02:12:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722935573; x=1723540373; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=/lfJgrSWKWbjRxr+WslEUzWg5lU4B6E1b6f6UsWxKzQ=; b=kiDTJYhrkfoT8FxrxNdJ9RqyVE5cR7vJBKcQ7Bdscxug8mmxMlCEqlH9XeszCqR+br ASAwc7YI2w4XVv8i6nxI39slge/UD6lguf3NZJnQLCg5wuRcOmo8iXztUTluWOD4LbkP SZvXySZxEWc4spQSnC6Bq1ETp/q9wd5w0XC6q94xfT6vywI70CLY8w3uecpmIwD14oBr NRjUuadbGGTuhcLyaHFmtf5RtENnuRwJEm8eV203Dr/KTpyCKbWo5VFuuBE6src7Rdnl B/R71zNa17puB3FXRxi+t1B2ewqZ6Ins0oMZ5yOFh72gXymxG0BNhQP3wJyfBc1lie37 41Rw== X-Forwarded-Encrypted: i=1; AJvYcCXuxDnqX2U1Hy6x1B1kMws5Ks3qwyqkt6ZG9ITkiqnZVRht22nCypwaWsR063XbUJ408aWYwYCXsY5I+dqzu07XZ2c= X-Gm-Message-State: AOJu0Yx1N6gaFcLt5aHLJObE7d+2E2IgJi20B1zUn5QNYhgcy9Zf3iGx g98PJ7CCQfNlLabh+uFjW04eHEa5EZdocQmnX5mnMqNQtWUvCZ6whtCp5S8e18HXF6g8zliJ1Ts bUm3afZV3P9vjbQWhLapgA1046pjuv1GnR6XdPetOWUiGAhHW X-Received: by 2002:a05:600c:3b92:b0:426:6388:d59f with SMTP id 5b1f17b1804b1-428e6f88ab5mr108831125e9.1.1722935573121; Tue, 06 Aug 2024 02:12:53 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFz4CyfbAAZQkhoC1wgEvzKNF6Rx7SFbNIZonf/EA7Io7uTPUsj76yKnyL8N6vgx9G44W9/9g== X-Received: by 2002:a05:600c:3b92:b0:426:6388:d59f with SMTP id 5b1f17b1804b1-428e6f88ab5mr108830885e9.1.1722935572584; Tue, 06 Aug 2024 02:12:52 -0700 (PDT) Received: from ?IPV6:2003:cb:c73f:8500:f83c:3602:5300:88af? (p200300cbc73f8500f83c3602530088af.dip0.t-ipconnect.de. [2003:cb:c73f:8500:f83c:3602:5300:88af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36bbd01619csm12403076f8f.36.2024.08.06.02.12.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Aug 2024 02:12:52 -0700 (PDT) Message-ID: <04bff7a7-3901-4adc-9f6a-466627cc1a21@redhat.com> Date: Tue, 6 Aug 2024 11:12:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/4] arm64: use IPIs to pause/resume remote CPUs To: Yu Zhao , Catalin Marinas , Will Deacon Cc: Andrew Morton , David Rientjes , Douglas Anderson , Frank van der Linden , Mark Rutland , Muchun Song , Nanyong Sun , Yang Shi , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240806022114.3320543-1-yuzhao@google.com> <20240806022114.3320543-3-yuzhao@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20240806022114.3320543-3-yuzhao@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 6173620010 X-Stat-Signature: 3pngjpx6fpfbdgsbiiga5nmnyrdrfi9s X-Rspam-User: X-HE-Tag: 1722935576-833566 X-HE-Meta: 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 dV4mpEbt BD2LJIMHTwGWBsPs+E1m0Ushur6ugmI6Zauab3Lh/uE6srbWg+NziPHWkkajfcv/htKAdjbb3Z98n2HJ/yFPjYzCLvaM9mUyhw9UhJIs2cd5s18Ex5Uwfc6Uv+kwCxsM/AkWMjmQk1Fay4eiJxEMEAzc4DZL2f8qS+9Yu2vCPOCiTjdwr0wHv6zRzRd+kcyNrHL6CPQD9fUrBUHwYLmz4/OT4Tb1k/KFUqpGssf5v/wYfLc4jv+eWg0Rd97W/Yhm7aHGkDWjuiMJ5YsJf5ihZuHbu9v6UVVsndLHP9LZ8VAal+JZB0/H2DdcdLtuAehuTpBVGjWziy4/yK5M= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: [...] > + > +void resume_remote_cpus(void) > +{ > + cpumask_t cpus_to_resume; > + > + lockdep_assert_cpus_held(); > + lockdep_assert_preemption_disabled(); > + > + cpumask_copy(&cpus_to_resume, cpu_online_mask); > + cpumask_clear_cpu(smp_processor_id(), &cpus_to_resume); > + > + spin_lock(&cpu_pause_lock); > + > + cpumask_setall(&resumed_cpus); > + /* A typical example for sleep and wake-up functions. */ > + smp_mb(); > + while (cpumask_intersects(&cpus_to_resume, &paused_cpus)) { > + sev(); > + cpu_relax(); > + barrier(); > + } > I'm curious, is there a fundamental reason why we wait for paused CPUs to actually start running, or is it simply easier to get the implementation race-free, in particular when we have two pause_remote_cpus() calls shortly after each other and another remote CPU might still be on its way out of pause_local_cpu() from the first pause. -- Cheers, David / dhildenb