From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59D203A0EB8; Thu, 30 Apr 2026 09:54:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777542876; cv=none; b=NpevtTxUnwybw5bs4eiGUmx6HB5V1PPB4WXDAONJ0tgzV/IvjLA1P+VtiJsgdnAOKfvdssXdpNVtuU1sL3rfgbDUjkWm7Xr9VmxqpLhQSDvMiDm2zd8Q9nAO/KGJtWH4DKf0SnoOjMx7kCAiK/TnbWZf5QX83AylpcUT3uVkg1w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777542876; c=relaxed/simple; bh=kcmvv0Zl7vQDtUGPG9gy11VWG9dOBfTGHblaASB3wYY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gXoqPq8PBLrNdc4O7cQcpBEuYa8EMa2axJ/71hODyG3V5O9VlyxkokjP3SHTloze7NeGnoo+qKQ6GqXDflqoXSPI41iEZ7jz7AMMGZu7saAFecTZWJF2O6jS6fYLBonDneDFeR3dQsx4aBrNrUf3Rb6a3Tzicel/v0AUN3ILe5Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=k48ftvrM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="k48ftvrM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1739BC2BCB3; Thu, 30 Apr 2026 09:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777542876; bh=kcmvv0Zl7vQDtUGPG9gy11VWG9dOBfTGHblaASB3wYY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=k48ftvrM8+rjMnTKWm51VnSYQ9LWvsDpQYF+Pe/a81FDALVZ0/28pe0iVbxyi4zhV mV5o3WGO7DoBlVI7MUSlKHn3V7rD3lSiYHyBZk4jmJFPB+dvoPlcm7jVK3tXLX/0Kz felCmXSJ9BeoCQuyaYeOfw4q8QzE5KgI2nGl3pUZZg+aZqcB9C6jNLVtcsQ+5AaXhm Eohfb7kYtIOnauMHAoWbAxB/1yPYXtd5TgXAFWkqlm/Fz2L/gzxl4SxP6bCExKqLR/ sgTQddrJeJusVOppg+ZLjebGTRVnwECjvxTri6CT2PyQL1CMjTSYFUuAslWX6OOSRz K70m8ba8YTnmw== Message-ID: <2d815203-a81e-40b4-92ba-31832c84c20b@kernel.org> Date: Thu, 30 Apr 2026 11:54:28 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/madvise: preserve uprobe breakpoints across MADV_DONTNEED To: Oleg Nesterov , "Daniel Walker (danielwa)" Cc: "Darko Tominac -X (dtominac - GLOBALLOGIC INC at Cisco)" , Masami Hiramatsu , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , "xe-linux-external(mailer list)" , "linux-kernel@vger.kernel.org" , "linux-trace-kernel@vger.kernel.org" , "linux-perf-users@vger.kernel.org" , "linux-mm@kvack.org" References: <20260429131522.4049054-1-dtominac@cisco.com> <889e4186-9f75-45d3-bd9a-1c90b218a635@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/30/26 11:16, Oleg Nesterov wrote: > On 04/29, Daniel Walker (danielwa) wrote: >> >> Shouldn't there be some sort of compensation or notification for this, or is each person that >> hits this suppose to just scratch their head and send a patch that's rejected? > > Not sure... uprobes assumes that it owns the modified page and nobody > can modify/unmap it, including the probed application or debugger. > > But may be MADV_DONTNEED should not set zap_details.even_cows == true > by default ? It should. If you do mmap(MAP_PRIVATE, fd), and modify some pages, MADV_DONTNEED must zap these pages. There is a recurring confusion about MADV_DONTNEED. The man page is relatively clear about the semantics ("subsequent accesses of pages in the range will succeed, but will result in either repopulating the memory ... or zero-fill-on-demand pages for anonymous private mappings"). But the initial sentence "Do not expect access in the near future. (For the time being, the application is finished with the given range, so the kernel can free resources associated with it.)" mostly only makes sense for shared mappings. Maybe we could emphasize that MADV_DONTNEED is not a hint but something destructive in private mappings. And that MADV_DONTNEED is not for memory reclaim, just like munmap() is not for memory reclaim. -- Cheers, David