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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43740C433DF for ; Wed, 20 May 2020 15:09:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F1D92054F for ; Wed, 20 May 2020 15:09:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726958AbgETPJG (ORCPT ); Wed, 20 May 2020 11:09:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726486AbgETPJG (ORCPT ); Wed, 20 May 2020 11:09:06 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2CE7C061A0E for ; Wed, 20 May 2020 08:09:05 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jbQKn-0003t3-NK; Wed, 20 May 2020 17:08:41 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 3580A100C99; Wed, 20 May 2020 17:08:41 +0200 (CEST) From: Thomas Gleixner To: Andy Lutomirski Cc: LKML , X86 ML , "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui , "Peter Zijlstra \(Intel\)" Subject: Re: [patch V6 30/37] x86/entry: Convert reschedule interrupt to IDTENTRY_RAW In-Reply-To: References: <20200515234547.710474468@linutronix.de> <20200515235127.404958221@linutronix.de> Date: Wed, 20 May 2020 17:08:41 +0200 Message-ID: <87o8qi4pae.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski writes: > On Fri, May 15, 2020 at 5:10 PM Thomas Gleixner wrote: >> >> >> The scheduler IPI does not need the full interrupt entry handling logic >> when the entry is from kernel mode. >> >> Even if tracing is enabled the only requirement is that RCU is watching and >> preempt_count has the hardirq bit on. >> >> The NOHZ tick state does not have to be adjusted. If the tick is not >> running then the CPU is in idle and the idle exit will restore the >> tick. Softinterrupts are not raised here, so handling them on return is not >> required either. >> >> User mode entry must go through the regular entry path as it will invoke >> the scheduler on return so context tracking needs to be in the correct >> state. >> >> Use IDTENTRY_RAW and the RCU conditional variants of idtentry_enter/exit() >> to guarantee that RCU is watching even if the IPI hits a RCU idle section. >> >> Remove the tracepoint static key conditional which is incomplete >> vs. tracing anyway because e.g. ack_APIC_irq() calls out into >> instrumentable code. >> >> Avoid the overhead of irq time accounting and introduce variants of >> __irq_enter/exit() so instrumentation observes the correct preempt count >> state. > > Leftover text from an old version? Indeed > The code is Reviewed-by: Andy Lutomirski