From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 DD65F379C50; Fri, 5 Jun 2026 09:31:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780651919; cv=none; b=VrnA85dvT/hby2xH/Am5vGvZzR+QJnnC1WqRDxbUtIQVPCLf76jdTwF2s6qiVZfIdyS5JeB0hNRB5BCglagLsvMlKMhqtIQ2i8JH3y4LqU0COMBPQxpLyHKcOyJkbLYwlSnLHUScuyCSPh/hE98za2YUKQSwArLOwOAz+GT/zaQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780651919; c=relaxed/simple; bh=o3pRW/wl0B1fwOfytl/JSDzzAs0Ose91NLb3SHMNvmo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CscGa1Xyw3w+/XY/3vE7o4rjiAJDuzcK0NsHVLQJApeNhr1J0oA0afdjrcUoHG15jXWVabWKX/pG/jPktKQVXuu8WVZMESSMiFwJwNdoBAjyl4VOCgXTj47jako7HjDZI3IreKP0zaBgyhIouULXz+CJ0Wzh62kNpF5j2yeNFCw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DNgiJnLA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DNgiJnLA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C7E41F00893; Fri, 5 Jun 2026 09:31:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780651918; bh=GdduqExShaT7dff5IoDbAyZHmANXhd+uGbGSM1erRXA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DNgiJnLAEJPr5JwKuY2/1gEfv9isFZJXBijEgs0PK0x9Umv2xGyhas/e1EZBgF2Ef vAEAQIT/GjcX0zYHMiR4puctAxje3RBaaeiVWH46LiA+av7Ii1+EU0DFX1VImMG0ZY r/3FVsnxAvCSoqGlJlI1NOAy1xWSF1FeITRrSRUoZM21wLGSsohNkF+DNrHstXghur SRo1KGUaZcP+9bDaXCtz5oMelFciV34HGwENGnXKQu4DySyuL20KvoQSxpvE1LO/KT rcbas1BoKwa/FzVUFWIhiTYA+NG5qrcHgZ5qkY4/UO/f+cZbJttw4cbd+6xsFE3Aoz OD/d2TvBSulEQ== Message-ID: <6f5265f1-d7c5-43b9-bd93-5066313704b4@kernel.org> Date: Fri, 5 Jun 2026 11:31:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/2] mm/process_vm_access: pidfd and nowait support for process_vm_readv/writev To: Christian Brauner Cc: Alban Crequy , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alban Crequy , Peter Xu , Willy Tarreau , linux-kselftest@vger.kernel.org, shuah@kernel.org, Usama Arif , David Laight References: <20260602100917.3641359-1-alban.crequy@gmail.com> <20260602100917.3641359-2-alban.crequy@gmail.com> <20260603082707.3831525-1-alban.crequy@gmail.com> <8e738cc8-dce8-4043-9b93-2bb867c43028@kernel.org> <20260604-ornament-sparen-biegung-e9930ee7444e@brauner> 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: <20260604-ornament-sparen-biegung-e9930ee7444e@brauner> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/4/26 14:49, Christian Brauner wrote: > On 2026-06-03 15:54 +0200, David Hildenbrand (Arm) wrote: >>> However, the exited-leader case is a real limitation for profilers. >>> OpenTelemetry eBPF Profiler wants to profile a process where the main thread >>> has exited but secondary threads are still running [2]. >>> [2] https://github.com/open-telemetry/opentelemetry-ebpf-profiler/pull/376 >>> >>> Using plain TIDs (flags=0) would work, but it means users cannot use >>> PROCESS_VM_PIDFD in this scenario. >>> >>> What do you think this patch should do? I see two options: >>> - Address this limitation in a separate future patch that fixes >>> pidfd_get_task() to use PIDTYPE_PID when PIDFD_THREAD is detected in >>> f_flags, benefiting all callers (process_vm_readv, process_madvise, >>> and any future users). >> >> Extending it consistently for that scenario seems like the right thing to do? >> @Christian? > > Yes, but I cannot vouch whether the mm operations deal correctively with > subthreads. > I'd think so, but I could give it a detailed look when reviewing a patch :) -- Cheers, David