From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4FE97C19776 for ; Fri, 28 Feb 2025 09:26:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/jeHPGx6jm3R1xDJMMDaYjvBALHQReLwn93izWT/Byo=; b=Q83o4krVfZXyS41kZ3Gu14d6Rh YTqFesDP2YBV92hApZVWHuDQIUKgNqIA4RYHP2ynPehnjBGZon80StUuYSBCQyL2yra2YIvlHjR1M jOdghlk5iclK/CHUW0ahHPCWEIJHFvPVKq45HFI2CP9bgi4slw8ddCwZbRVlAZ3uKC2wriwt0794m DfLQrHcLBOcbmllD02gIl6qIu2Ki20PAqfWvijfp+DdZfJKw+/SNpPjXSK17PAWncixEQ96Z2mNkS pkl6jNunBSSeu1aWWaeO/8Q66dOLYScudLt6z+GkCxPZ43GOJJcrQCn1zJlybeDQKl5AJjYlWZ7Xg 8dh+auvw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnwdI-0000000AM6x-0YJS; Fri, 28 Feb 2025 09:26:12 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tnwbL-0000000ALdh-20fj for linux-arm-kernel@bombadil.infradead.org; Fri, 28 Feb 2025 09:24:11 +0000 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250228091509.8985B18-hca@linux.ibm.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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).