From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 C098E25335E; Fri, 28 Feb 2025 09:24:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740734663; cv=none; b=lOIjdSnTH0BvZjKYaxdKNzcKL9h1nmE9DSWC40fdyBYpPPyXN8s2ieLKkbSaZS06nL98fkqjoQQurURf2KLTJ7goC9uUmG9szHqN4sdUF1CkldtPCFtPK78apsqqCX9HrWwK8/aXgWFiPYm6SU4soBTTPHnIJGoVsU+ragwOEUk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740734663; c=relaxed/simple; bh=/jeHPGx6jm3R1xDJMMDaYjvBALHQReLwn93izWT/Byo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=K3nxNTGJgXWRGkTndFnGMCFISUT1tCd9SUZhXmwEUtKnHS5rl15lR1uXf+kWn9u0KSwD0mfiA1kWM999Cv2AQBKHrib7xu2bc0XKqpN54ScllE3MDVp6r5u2d5o3F3/8zUw3bTNYDUcfuLdzoCuzS1bLVzReoe5OjaZs6YO1bc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=lGT3I5C6; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="lGT3I5C6" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=/jeHPGx6jm3R1xDJMMDaYjvBALHQReLwn93izWT/Byo=; b=lGT3I5C6xKvNBqb7eUq6t1oyMA TKIoHFnWDeq6k809BZtIhypUMx/9yIkACdkXQsfqZYh7cwTuKb8ur/v3r/e5h0DhBJ7GTxELBBPEU PTDcCY+uNMxYO7Xe+1tKuuw7l8JEuOEXdotDmQ4ZVDppqjXNnkVBRnI2BabPZrL1epAJperOINnok HMNUOGxzSMonqZ/qtdGSBxtHwSbHx0UdOrL4iRIGbukCttTLYAOvEFxW0+Egs5aypmVtYUFOJ9K/u w8uSkvz+kQfsap8Fz6keuxovTlnUfUO3DPZs4jiUEUryiItJ/OScuvrcSrd/yiSegPuDFjnc0M7a/ VThUpajQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tnwbG-00000003wMH-2wNy; Fri, 28 Feb 2025 09:24:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id E673D300756; Fri, 28 Feb 2025 10:24:05 +0100 (CET) Date: Fri, 28 Feb 2025 10:24:05 +0100 From: Peter Zijlstra To: Heiko Carstens Cc: Lyude Paul , rust-for-linux@vger.kernel.org, Thomas Gleixner , Boqun Feng , Catalin Marinas , Will Deacon , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Ingo Molnar , Borislav Petkov , Dave Hansen , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , Arnd Bergmann , Juergen Christ , Ilya Leoshkevich , "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" , open list , "open list:S390 ARCHITECTURE" , "open list:GENERIC INCLUDE/ASM HEADER FILES" Subject: Re: [PATCH v9 2/9] preempt: Introduce __preempt_count_{sub, add}_return() Message-ID: <20250228092405.GE5880@noisy.programming.kicks-ass.net> References: <20250227221924.265259-1-lyude@redhat.com> <20250227221924.265259-3-lyude@redhat.com> <20250228091509.8985B18-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250228091509.8985B18-hca@linux.ibm.com> On Fri, Feb 28, 2025 at 10:15:09AM +0100, Heiko Carstens wrote: > I couldn't find any cover letter for the whole patch series which describes > what this is about, and why it is needed. > It looks like some Rust enablement? Yeah, more or less. It's replacing local_irq_save() and all related functions (spin_lock_irqsave etc..) that take a flags argument with this new thing that frobs a recursion count in preempt_count(), obviating the need to carry the local flags argument around. This is nice, even for C code, less flags muck to carry around. It would be even better if they then went and deleted all of the _irq / _irqsave nonsense entirely. Yes, that's going to be a big patch :-) Also, IIRC there is some arch stuff that comes unstuck if you do this blindly (I tried at some point, it didn't boot).