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 55CABC5B543 for ; Sat, 7 Jun 2025 13:42:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D3BB6B0088; Sat, 7 Jun 2025 09:42:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 984DF6B0089; Sat, 7 Jun 2025 09:42:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 89A9A6B008A; Sat, 7 Jun 2025 09:42:19 -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 6AFC56B0088 for ; Sat, 7 Jun 2025 09:42:19 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id CBB59122111 for ; Sat, 7 Jun 2025 13:42:18 +0000 (UTC) X-FDA: 83528718756.21.2E53073 Received: from mail-qk1-f170.google.com (mail-qk1-f170.google.com [209.85.222.170]) by imf02.hostedemail.com (Postfix) with ESMTP id 15A5D80003 for ; Sat, 7 Jun 2025 13:42:16 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b=OAR5Dj8v; dmarc=none; spf=pass (imf02.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.222.170 as permitted sender) smtp.mailfrom=jgg@ziepe.ca ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1749303737; 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=59D9xyE1wMBpDDtvice5CrCodJL07qD5HLVD9Zhx6wk=; b=ZWWxNu7vJb0sPeOTGFVCJPX0704nmTHr9NcXpYDPy5uoQE2eoXOSGRZOeoyxhxK93h0MhM vmBRyK0tIfoqpydI88/jmuf9VdQsG5DwJh+qwIMRN/jAfB63iTdHME7W98MRK358U1rwMe kJrPQEFbHCVK45fbymhNevUMRMXMszI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1749303737; a=rsa-sha256; cv=none; b=PKWY/q2epNjB0Pwm4WZ45AR5jvZe2Dk0CvvuJBkONS64dRJpPukqWWszKHErY5zO61brjy N4ggrZLlQWop5/NP086czYT7Z25xlrzMcGCo1+iijD9Nylu872wTlcp6CjkG1rvrjlLYp3 /M5BblGyuRZFSFaRXmhKveoweUp4t4A= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b=OAR5Dj8v; dmarc=none; spf=pass (imf02.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.222.170 as permitted sender) smtp.mailfrom=jgg@ziepe.ca Received: by mail-qk1-f170.google.com with SMTP id af79cd13be357-7d0976776dcso286476485a.2 for ; Sat, 07 Jun 2025 06:42:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1749303736; x=1749908536; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=59D9xyE1wMBpDDtvice5CrCodJL07qD5HLVD9Zhx6wk=; b=OAR5Dj8vEpUlUgZ18pEozP/JAN2rD+4d/s4j6FfZveZ9Nq2i0aAf/v1PiJmG2+2lm+ Hq9/baAQL/KbzGIOkFqXQyZKJsk95lunoyw4+2RbnArau5Y1rJcIiBq3LQ2RDcCaC4Y+ zzVJKn+Y1u3xmIzeu6uPliHg14e8A90se6xKIDsQuNpVGqKurpLBcdFs2qZLtEnrZfS+ uDJrbqMUInLWEF2L6q1HiUCf8TDLDK9m5lqww1Z8PPtZyVykfi7oLlYcDiHCTup6vAS9 6ox92mavNTGid8JYktqM454E5TfJFgwY5YW7Xn2ZBoAKjL8Lht61/y3IjZuuN5evj00z VfJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749303736; x=1749908536; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=59D9xyE1wMBpDDtvice5CrCodJL07qD5HLVD9Zhx6wk=; b=IZlLqPa6HNBZpOcFKcxtrtmdY6Qhor5NJYQ0Uo/OBgSHmbpxRcTvLkgUyxqOo3BsC/ 0sAfnOZuqgg1z4fuAYSqaAyby5AvkMV8t3jbWDmqKd2x6tsiEsGGkBYkzrylzxn5HlyV NdqLJAWiw3meUJIdC0TpvJxTYa2RCGFW2w1XmAtmpdjdc2TSqFvTIjgErszygikijcbw +dxA8IlST+OH7Y6L1HjqgarODbv5CbbsrRz/0tXA+8yL6PxKQj6aNuUphzJFRoRzITrz eKEwYZpMDqDoPglQvr1/u+36pFKGE7PsoccVN5ty1nwueSH+j6Hxvb9dQ3hPz3TS7TaQ owEw== X-Forwarded-Encrypted: i=1; AJvYcCV2G7lBpIALNJmZGcrm++bs7mJULDia7AJJMXHFc6cRrcbwYOh8F0FJwZSwVjNhQPDmVx3gzlSgoQ==@kvack.org X-Gm-Message-State: AOJu0YyxFvUhELLlVv6YPww8tb7jY5SMRMhPDa5aKQxPabuPNJ1tTO00 ApwnG8CYClNzqlztIcWVnhNWyXGMuPznpS0WlXzF7LI5AcQgXATOH1/KajJQpu4OJEk= X-Gm-Gg: ASbGncvngLMzK1mYwbcQ6nxUFMlCTqmLCc3BmpsnnrCmPHJL42C3FqKWjIf/1O7eiFc bQaCIRxNHF+86M+OGGPMG23IS2g3rQx6b+qlIEyBSUyk+FRKlQMfUccInLFPothfdWQaOoGviNV MUEL+UO2I0k5FQDhOFxz3XFvA2yOjQRHnA/f/Li3ljZntIEEnDpiD1T4PNfvxfsroh6Kt+mNmGv IOcSVWw66HOZR4FlVnh2qcqicxDGujbBOqMknoE8Ty8hQmWUf8gcyc1Zi5Rjy03I7/YOXjA3o1/ PDomCEAqiE5dqLKXo5EEwKwBHbMt4n4noysBaYA2Ib1RsuevYvE9c7obI/6nSFcqJugMP1GTfwT s6FD+YCkKLKzlspVx0uimyQq6/GJLjRNeQZojsA== X-Google-Smtp-Source: AGHT+IFj0uOzC7Sid/wwlvtMxCBAxx1olyUujdYH0dZwO5keyJkCZDQG3GgsjcfeLCsHn+4VITCkWw== X-Received: by 2002:a05:620a:aa0b:b0:7d3:8cc5:8a44 with SMTP id af79cd13be357-7d38cc59db9mr119292285a.29.1749303736118; Sat, 07 Jun 2025 06:42:16 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-167-56-70.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.167.56.70]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7d38c067179sm74899185a.73.2025.06.07.06.42.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Jun 2025 06:42:15 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1uNtoM-00000000jpZ-2C2C; Sat, 07 Jun 2025 10:42:14 -0300 Date: Sat, 7 Jun 2025 10:42:14 -0300 From: Jason Gunthorpe To: Lorenzo Stoakes Cc: David Hildenbrand , John Hubbard , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Peter Xu Subject: Re: [PATCH v1] mm/gup: remove (VM_)BUG_ONs Message-ID: <20250607134214.GA158671@ziepe.ca> References: <1a7513cf-4a0a-4e58-b20d-31c1370b760f@lucifer.local> <72bb36f2-65b6-4785-af9d-5b1f8126fc78@lucifer.local> <2f866f12-2aa0-4456-b215-08ddc9b13b1e@redhat.com> <3dfbbd63-697d-42aa-8906-539d74df9123@nvidia.com> <44af8f5a-2d94-498b-a3e0-31f5dde74538@redhat.com> <20250606184212.GB63308@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 15A5D80003 X-Stat-Signature: aofsbzez59sba9wfrqubk9x1ns64dyd4 X-Rspam-User: X-HE-Tag: 1749303736-935718 X-HE-Meta: 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 D7Ltfw2g LxjxendUZkv4i7C3ziS48zAZj4LFHpXa/Iyo0 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: On Fri, Jun 06, 2025 at 08:03:15PM +0100, Lorenzo Stoakes wrote: > On Fri, Jun 06, 2025 at 07:46:52PM +0100, Lorenzo Stoakes wrote: > > On Fri, Jun 06, 2025 at 03:42:12PM -0300, Jason Gunthorpe wrote: > > > On Fri, Jun 06, 2025 at 08:23:25PM +0200, David Hildenbrand wrote: > > > > > One last data point: I've often logged onto systems that were running > > > > > long enough that the dmesg had long since rolled over. And this makes > > > > > the WARN_ON_ONCE() items disappear. > > > > > > > > I think what would be *really* helpful would be quick access to the very > > > > first warning that triggered. At least that's what I usually dig for ... :) > > > > > > That's basically my point, it doesn't make sense to expose two APIs to > > > developers with a choice like this. The WARN_ON infrastructure should > > > deal with it consistently, maybe even configurable by the admin. > > > > > > Keeping the first warn in a buffer is definately a good option. > > > > > > Otherwise how is the patch author supposed to decide which API to > > > call in each case? > > > > > > Jason > > > > To clarify - are we talking the first instance of a specific warning, or > > the first warning in general? > > OK sorry I'm being dumb, it is -per warning- reading the thread :P > > So I guess you would have the macro establish a static buffer for each instance, > and then some interface for gathering those up and outputting them? Honestly, that seems unnecessary, just a single buffer for the first global warning. Maybe with a 1 min rate limit for replacement or something. The kernel doesn't run around spewing warnings as a general rule. > And I guess we'd not want a new interface for this like WARN_ON_ONCE_STORED() > because that'd be... weird and how would anyone think to use that and nearly all > cases wouldn't. No! Delete WARN_ON_ONCE and say the new global mechanism is good enough to capture the first WARN_ON, everyone always uses it always and then nobody needs to think about this anymore when writing new code. Jason