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b=M47S5qYCUeNu9zAEEEGxe3TUf2qe75XDnFR8oChGw00D70OvdWBxteGMyKoiEb5glkdO4v7HSw3eYUswweilNpXdVCZNPfVz3jxb0dLPwPtn8VyI+I41D+VKsVUdQzgklS5J6lYMhhZhUeNVg/KGxVbKi3X4neKVJS5A2PtvAwOAJPV6wmsa/yV+rTuFag0sF9dlGiFIbYLvsRSjPIB2tDHwMZva7w/iVSSXhxar1tgF1NLMUPfJbEpvWgcMn/K7eQDK9rYHN8HQ1LOAGGUifOpRSuuK8Xe9JoyME5T/lghSpW0TjZNKwroBMnVvIKrNBbNAwo31ASszlelihI82rg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=efficios.com; Received: from YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:be::5) by YQBPR01MB10579.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:75::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9253.19; Tue, 28 Oct 2025 16:02:42 +0000 Received: from YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM ([fe80::50f1:2e3f:a5dd:5b4]) by YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM ([fe80::50f1:2e3f:a5dd:5b4%2]) with mapi id 15.20.9275.013; Tue, 28 Oct 2025 16:02:41 +0000 Message-ID: <76b1c0f3-6117-4554-9b9a-cf49df1b5791@efficios.com> Date: Tue, 28 Oct 2025 12:02:40 -0400 User-Agent: Mozilla Thunderbird Subject: Re: [patch V5 10/12] futex: Convert to get/put_user_inline() To: Thomas Gleixner , LKML Cc: Peter Zijlstra , Darren Hart , Davidlohr Bueso , =?UTF-8?Q?Andr=C3=A9_Almeida?= , kernel test robot , Russell King , linux-arm-kernel@lists.infradead.org, Linus Torvalds , x86@kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , linuxppc-dev@lists.ozlabs.org, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Heiko Carstens , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org, Andrew Cooper , David Laight , Julia Lawall , Nicolas Palix , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org References: <20251027083700.573016505@linutronix.de> <20251027083745.736737934@linutronix.de> <0c979fe0-ee55-48be-bd0f-9bff71b88a1d@efficios.com> <87frb3uijw.ffs@tglx> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: <87frb3uijw.ffs@tglx> Content-Type: text/plain; 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This might be replaced by a regular get/put_user(), but that needs >>> a proper performance evaluation. >> >> I understand that this is aiming to keep the same underlying code, >> but I find it surprising that the first user of the "inline" get/put >> user puts the burden of the proof on moving this to regular >> get/put_user() rather than on using the inlined version. >> >> The comment above the inline API clearly states that performance >> numbers are needed to justify the use of inline, not the opposite. >> >> I am concerned that this creates a precedent that may be used by future >> users of the inline API to use it without performance numbers >> justification. > > There was not justification for the open coded inline either and > converting it to get/put must be a completely seperate change. AFAIU there was justification from Linus in commit 43a43faf5376 ("futex: improve user space accesses"). Perhaps it's good enough to refer to that prior justification in the commit message. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com