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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17AB2C77B75 for ; Tue, 9 May 2023 20:11:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229695AbjEIULK (ORCPT ); Tue, 9 May 2023 16:11:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229618AbjEIULJ (ORCPT ); Tue, 9 May 2023 16:11:09 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6479A1729; Tue, 9 May 2023 13:11:07 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1683663065; 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=GDHRmjiERMZtAMWS8NswxcpsZgr8pqyf8cBJN0UwKq4=; b=qRz1Wt3JIbNYLISqAbJr1CMERh+G2fMl0sqNUINGFnuAglUDS20PR5mShGM7iQQQaOXzUO 6p1nBmlJSh5FISuh/gxPpyFl5N/5lIcPzXiWCbOhc/BY9nLjejGZdozuMFQuDWHB0czbQ3 N334596N1dIxTBUtYyzDiKqjfnYYlcCALsa05iyDdZ772j72RpkHn+oDxyP4ObL7l+piSu ZhZkepOsryy7f/3f8Xvt0ySi2CMPDVnx0tsF8XLS0QXVKSABEb0ZDeaHvlrFZfnZHg6sEY EkUkcA416BPYsfyNhOSk3xIjz0pEBaTy2eNw1t0P+tqJe8e17B+vC1YPI9z1/Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1683663065; 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=GDHRmjiERMZtAMWS8NswxcpsZgr8pqyf8cBJN0UwKq4=; b=Xlcesbr/mowxxv4d+xv21wM9Nh14MEM6CP2UULmrKClB0/ijd/XoMlkIURymgqxjfMwTM5 2x4mgfol9jpnTzDw== To: Peter Zijlstra Cc: LKML , x86@kernel.org, David Woodhouse , Andrew Cooper , Brian Gerst , Arjan van de Veen , Paolo Bonzini , Paul McKenney , Tom Lendacky , Sean Christopherson , Oleksandr Natalenko , Paul Menzel , "Guilherme G. Piccoli" , Piotr Gorski , Usama Arif , Juergen Gross , Boris Ostrovsky , xen-devel@lists.xenproject.org, Russell King , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Guo Ren , linux-csky@vger.kernel.org, Thomas Bogendoerfer , linux-mips@vger.kernel.org, "James E.J. Bottomley" , Helge Deller , linux-parisc@vger.kernel.org, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Mark Rutland , Sabin Rapan , "Michael Kelley (LINUX)" , David Woodhouse Subject: Re: [patch v3 08/36] x86/smpboot: Split up native_cpu_up() into separate phases and document them In-Reply-To: <20230509100421.GU83892@hirez.programming.kicks-ass.net> References: <20230508181633.089804905@linutronix.de> <20230508185217.671595388@linutronix.de> <20230509100421.GU83892@hirez.programming.kicks-ass.net> Date: Tue, 09 May 2023 22:11:05 +0200 Message-ID: <87fs85z2na.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Tue, May 09 2023 at 12:04, Peter Zijlstra wrote: > On Mon, May 08, 2023 at 09:43:39PM +0200, Thomas Gleixner wrote: > Not to the detriment of this patch, but this barrier() and it's comment > seem weird vs smp_callin(). That function ends with an atomic bitop (it > has to, at the very least it must not be weaker than store-release) but > also has an explicit wmb() to order setup vs CPU_STARTING. > > (arguably that should be a full fence *AND* get a comment) TBH: I'm grasping for something 'arguable': What's the point of this wmb() or even a mb()? Most of the [w]mb()'s in smpboot.c except those in mwait_play_dead() have a very distinct voodoo programming smell. Thanks, tglx