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a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1761666964; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UuJ043THRvtCeNNEXMyo9HE4WCxrom2sWKd3gBR4LJU=; b=OzfJrQmaGSYN7SjKtIVGt8XfMPuNg4JidCQ8tWQK7AVcOCmFMWTyt7m3oaUqsJxpyM0pab +9VYgPLRugbHDX88KcBOysbJ/aq1qSI58eSdNkEqVOW7qjKTKIUy5Dlk/fxAOLwId5eUGL MMCc/R6qmw7qog3LmZOpn1hDbjFJ/yfaXhgNJR3gCLTsi/v5MgAafS4ZxWm/T3HYbhDBYz 7c21YHT0Nu/Sjny5kfjGTXYYbNGtZT06Axwaf1pQQ7shqgfmdljAo2APs5uuRC3KZQDlgK uYX1vd7MjyQwAwEqJ1sI+OyJphVkD9lM3WBrKG1nbnqWkrsRgH5c5NF/n8hOYw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1761666964; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UuJ043THRvtCeNNEXMyo9HE4WCxrom2sWKd3gBR4LJU=; b=+BHGZAi3yNFrAvpwe9vwol5p0lVACxAmOqomEwb4Pm2KqtlBgDYqoGb8xyRWB/0XxRQyXl VePkBymJj4BQJSAg== To: Mathieu Desnoyers , LKML Cc: Peter Zijlstra , Darren Hart , Davidlohr Bueso , =?utf-8?Q?An?= =?utf-8?Q?dr=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 Subject: Re: [patch V5 10/12] futex: Convert to get/put_user_inline() In-Reply-To: <0c979fe0-ee55-48be-bd0f-9bff71b88a1d@efficios.com> References: <20251027083700.573016505@linutronix.de> <20251027083745.736737934@linutronix.de> <0c979fe0-ee55-48be-bd0f-9bff71b88a1d@efficios.com> Date: Tue, 28 Oct 2025 16:56:03 +0100 Message-ID: <87frb3uijw.ffs@tglx> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain On Tue, Oct 28 2025 at 10:24, Mathieu Desnoyers wrote: > On 2025-10-27 04:44, Thomas Gleixner wrote: >> From: Thomas Gleixner >> >> Replace the open coded implementation with the new get/put_user_inline() >> helpers. 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.