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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9A3D8C43458 for ; Fri, 10 Jul 2026 16:47:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8FF4C6B0092; Fri, 10 Jul 2026 12:47:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8AF496B0093; Fri, 10 Jul 2026 12:47:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 777576B0095; Fri, 10 Jul 2026 12:47:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 501256B0092 for ; Fri, 10 Jul 2026 12:47:48 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id E97A38F1D4 for ; Fri, 10 Jul 2026 16:47:47 +0000 (UTC) X-FDA: 84973448574.01.100FA68 Received: from mail-qk1-f182.google.com (mail-qk1-f182.google.com [209.85.222.182]) by imf04.hostedemail.com (Postfix) with ESMTP id 1C0D140002 for ; Fri, 10 Jul 2026 16:47:45 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b="K/0nc6m1"; spf=pass (imf04.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.222.182 as permitted sender) smtp.mailfrom=jgg@ziepe.ca; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783702066; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ldYpDeT5zs3T98XMfsT8ni9uE73SXe2oYxwTATvCf1s=; b=D7lgELme2Zu+jVBMySnJNpF5/bF87N99MPfE0ZsBcn2P8OPVKkrduADOajCJjVhgNyCACl Scpkpg5y96O9DC8GUBD86/H4UQaOD0unSbdoQHruaX5ZEDlxp1EMGJVwADF0gf5/JmiDWN 4VakS1FGsDzxggW/E/bas5ZpF/mlq0Q= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b="K/0nc6m1"; spf=pass (imf04.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.222.182 as permitted sender) smtp.mailfrom=jgg@ziepe.ca; dmarc=none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783702066; b=iRRSf1J0/B1TPGjENJqKokmjb7sqCEH8kMvWfowV3JuRQvBA3sgTeYuXMyJ2DJlDli7Z2h 4flS8SOTqgD2cSypeIQWUvSg6LCfPXZ0lq9fRk4fdeAAhXJw0T6Ru8xR55w9tKyqjIWCMN 37seLDaJ2PwwVg+3TB42ASCgBxQ72OA= Received: by mail-qk1-f182.google.com with SMTP id af79cd13be357-9204711e831so93963685a.2 for ; Fri, 10 Jul 2026 09:47:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1783702065; x=1784306865; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=ldYpDeT5zs3T98XMfsT8ni9uE73SXe2oYxwTATvCf1s=; b=K/0nc6m1/2uJoTXzWE/XHoZLqezt96mWtmEDBLR/KNQkcBNRefom3KyaSuI44lg9kT vZTPYnSFE/uCVxMpzXfBZ3nVa+I9haBO9LIMYx0VUJrJz+P7qMJhf/G9k/LSeOAIaoxr ScX5VlbzTtSbvaSNSxBO2K+N9RWoagG2oROiTBOhJwIEWxU+7AUmDQB0NF4hcJUN6lmZ KpRCk225R7BJKyBcGMVQY8STBPTygqzjJMjGm7vkQmMGYrVbi8eOhYLAShABd4tPchMj DNzxTY504KveqzB2Fsaiu7p9oHNzEGfgZAY+aacYcQ6OWsjB3T3h0lpmqLr2iW9sfz04 35KQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783702065; x=1784306865; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ldYpDeT5zs3T98XMfsT8ni9uE73SXe2oYxwTATvCf1s=; b=nWwepNFzn8QmCpPD8KGh1UClaRZlq8+ooZn+wG1QeBkBIX4NXwm7Lwnb2a42ejrwW0 x0qAVLoGn9Hl5a9QhWINNRdqVTAHKs42iKyOzPzSc3lN7PGsMNDF0Ri6pfCDa0dtoRMC y13EJrJshltYVZyHKsTMnuHmTJbX+SgopnCyfIzC4ywG03ciYJe+cV3L8q2vfXMyzoqN 94/5PINsrr8tizP/StbzLbnsa++UL8KsLAbdpFhrPg6D6pYxN0S5P3wwIUgQTwAoAR2U ntnTntJ8ot60ze9xrsX5gCCKOqEhnR0mXsvfXsRZyMMXVToYUDN79x+7UvscjdKp3CRf nXdA== X-Forwarded-Encrypted: i=1; AHgh+Ro9w6Blhm7BbVW9Igtlaw4byr4q/CFbIJL23IZflwY2NKIrJvtg9o/GutsmFz6U0VSzD3sLwxh6fA==@kvack.org X-Gm-Message-State: AOJu0YxRByJ+PbLlZP3/zZHJxK+hjY7NwkPAOnFikglBHpfsCfIUf9in Dlwnu6D9c2gi+QmA2Nd+83YzUhDlsYUqBjdPqN3PQEvQlahPU4PqvEM7KIPhtf133OE= X-Gm-Gg: AfdE7ckXNd66MpIJ1raa3ZvcZCgfJGdDPLA8o4eTfQoNv+uCbP63eEcwVHBTNziflN0 fEoTyqoZew6me0CYYwobf2qIdcCrZsa8cTj2NM0WgDjcjviNXYJNiz+BkzBGsDjqavPt1XeBRrI IClDzJPHERNZZQXRIUTnewXfQYsj5qZ3uypanzLfpbzlpT4icYzxUioRRd9ieayb2a47PLIgwuD 5mzQxsS3RVzSjGEKaiR74is22Q0GsUh6D0/di3fzyGROOJpc4ope1Ilye1d8AkxaHx/9P+2f8hd A6wTLJEeAZ6gHDRBwU9BGoLNhb7W40z0N5GyZMIorXb/4N3nmMSboTvFlVjy50aDRup49kjHhGW 5a/Nf8LQ0MVTmiYj6tk7Qjg3sbUi4V76J5xPB+7AK0KG4b0ZawI77I4WlbHRb X-Received: by 2002:a05:620a:4044:b0:92a:3ceb:9cf1 with SMTP id af79cd13be357-92ecf68b839mr1385461685a.37.1783702065110; Fri, 10 Jul 2026 09:47:45 -0700 (PDT) Received: from ziepe.ca ([159.2.72.92]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ffd5bbac2asm45778726d6.21.2026.07.10.09.47.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 09:47:44 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wiEO7-00000007ZDn-3hnt; Fri, 10 Jul 2026 13:47:43 -0300 Date: Fri, 10 Jul 2026 13:47:43 -0300 From: Jason Gunthorpe To: Stanislav Kinsburskii Cc: airlied@gmail.com, akhilesh@ee.iitb.ac.in, akpm@linux-foundation.org, corbet@lwn.net, dakr@kernel.org, david@kernel.org, decui@microsoft.com, haiyangz@microsoft.com, kees@kernel.org, kys@microsoft.com, leon@kernel.org, liam@infradead.org, lizhi.hou@amd.com, ljs@kernel.org, longli@microsoft.com, lyude@redhat.com, maarten.lankhorst@linux.intel.com, mamin506@gmail.com, mhocko@suse.com, mripard@kernel.org, nouveau@lists.freedesktop.org, ogabbay@kernel.org, oleg@redhat.com, rppt@kernel.org, shuah@kernel.org, simona@ffwll.ch, skhan@linuxfoundation.org, surenb@google.com, tzimmermann@suse.de, vbabka@kernel.org, wei.liu@kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH v7 2/8] mm/hmm: add hmm_range_fault_unlocked_timeout() for mmap lock-drop support Message-ID: <20260710164743.GX118978@ziepe.ca> References: <178345345668.660027.2952911919681614557.stgit@skinsburskii> <178345362182.660027.12809852179204464964.stgit@skinsburskii> <20260710162749.GP118978@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260710162749.GP118978@ziepe.ca> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1C0D140002 X-Stat-Signature: bf9wqc689xyqx5j3m3xswraxf1g381of X-HE-Tag: 1783702065-754019 X-HE-Meta: U2FsdGVkX1/keKcyNnoICO0xUXytUyEB9gdni9ivXHvwfTzV6+M/U9MOrrpkca+KWNugmFYXdQtz7rL5KXzpUbjOTV/JJwYGD6xgasj+onvHep7uDYFkVkwtDbGQhAZ2ltHWhDzq0ukf7HRfvCgPDYVOy7Sh1r0avyC0M+INxJPMXTMS4T0OFoC7X9OJYQUyqEb4HG7S9h22lIN4Sq8qtSSOj6tNr/qDfbQgRRxafm/hxx2VYhA7Zc3y8f2qX5korNaO6btHN0xvQdMr2Q7rl7WU/n3QKlkjr7qzrMqxMtWqp44b2f2k9iE9LIkx6JgpaeZjovA4jdFKmj/Xg3BoOw8n1l0JMsslrszm3E2HhMyhRxhLZtJdejXigUDsW2TOTI/QbQS+9g6a+5FQltcKKVTiQka4BAArE7kjNrSX1f8SVL7AXtmI7E3XB6fmoefJfI39cj6o6nZ23J5sltAvY3ojgK1huy8mTAtl9FLCTbt5yPer2S3uPDG5QerO4Fn28kyJg2YM+Z21pR4f1lD8dqfZ+0/EQTA5oabISrCmBiGjdJUjBbV4g/AgChWX4ri1Tjmn2m5aF48eDZzyuvIpejbbDt1IAzSRErvolbCDQLZ8UbsLX1XT22RLjDnmbRRwzT03YvOAVahrZmkVzlyDCXuhdOZGkhOWmDTyzU4JKoTrmdZNTfGkdaotZ8iScSd9SLk+V4GXhy6PfjfEwLIot9wltUkzKZUB6qUlD1zuRtjLHu2eLuWP/uQFeny+6jJL1x9/Ai6AHRb+t2YxzBjQUluvl5fatZQqh/yOHjZKhOS2iwbsGgvGDo2fXhoZpPnRnyjsUk6B2BWXp8Vkh44P1TVD1NtwJvAuHLD1OXd/kYO/hzd9uT+r1FDtbV4rU27Gh9RYmGr+jPmAOQG7uvtmfod+zS3TV/UrUUb6+1JJp3XwIanPhKNRb5nKJp9+vk1JhZtqoCaYfSzPPFLoSzE TTwcQSs0 vTuWo72Dm4VXQnFwueF8L+6QpGIlvhCDYDqAnNRwv7I+dO1ab/riX7/MTDDCCjWUybq8O2Zsztk9O7iz+irftL0cQIci8U77bl3JkELTteuc8z6LEPp3H/V+Z3MGFUyZxR1o293vMW3t4X3roSImxqhxzi4p45S1KHSoh9lFO6ro+s9ZLVPaKW9zvcx7iTXqmAuzPkkEW8f+sOuqFd1BILLsfVJbmiCWEQ+CK6uSP2Ms81JSjoU8x99g2Yk2CH+hdvb63KDA9JUZx2sZRhQvTu9QEXwoZEQjRN92oQzsWEC2iDNt2yPQk9eS/vSUlNAFD8ueb1No0nmi/hWE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jul 10, 2026 at 01:27:49PM -0300, Jason Gunthorpe wrote: > On Tue, Jul 07, 2026 at 12:47:01PM -0700, Stanislav Kinsburskii wrote: > > > +int hmm_range_fault_unlocked_timeout(struct hmm_range *range, > > + unsigned long timeout) > > +{ > > + struct mm_struct *mm = range->notifier->mm; > > + unsigned long deadline = 0; > > + int locked, ret; > > + > > + if (timeout) > > + deadline = jiffies + timeout; > > + > > + do { > > + if (fatal_signal_pending(current)) > > + return -EINTR; > > + > > + if (timeout && time_after(jiffies, deadline)) > > + return -EBUSY; > > I really dislike there is a timeout here, HMM is supposed to be more > deterministic. GUP doesn't have a timeout, what is this about? It looks like you've moved the timeout processing related to the mmnu notifier sequence from the callers into this helper. I'm fine with that, but maybe add some comments that this timeout is helping implement the mmu notifiers, and we do expect that the HMM part will not timeout. Though it is a little hard to see how your stated purpose of enabling userfaultfd is going to work, aren't you pretty much guarenteed to hit a timeout if the userfaultfd process is adversly scheduled? That's going to end up broken. So, maybe the deadline should be resetting after every handled fault? ie the timeout really is only about the mmu notifier and we don't count the time spent handling faults or walking? Jason