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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 03B1AC433E0 for ; Tue, 30 Jun 2020 12:01:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9F2720774 for ; Tue, 30 Jun 2020 12:01:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Zg1PSEX9"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="+zw99FP6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733281AbgF3MBD (ORCPT ); Tue, 30 Jun 2020 08:01:03 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:54974 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732746AbgF3MBC (ORCPT ); Tue, 30 Jun 2020 08:01:02 -0400 X-Greylist: delayed 5913 seconds by postgrey-1.27 at vger.kernel.org; Tue, 30 Jun 2020 08:01:02 EDT Date: Tue, 30 Jun 2020 14:00:59 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1593518461; 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=qgnrybG2OslXjy+mHoLg62UfvNjCsSTc6swzuIPA9nA=; b=Zg1PSEX9eAg0idNefX0ymPyDemrl7pZ1V/pqk2wD2wPT0Gd6gN7h/HTZ6Z0puEgyBs819Y 2CO0SZoNgvpujfod/iS+cjnyNW/iQIRJysaJYniWBcy9IAVmWwgYYl86N7MW05RJbaJMgR r3Dvw9cRspfz86I7dMsEcgNBrpgdqfwpTHvoOks4IyDsgKpvzFZ2TvzCFbrGeodzI8esPz yUCbbINqvUtisoQuL7fl2brJmsUkn6vGrCVEUPRCp4fr9vjbfqKTfgeVsR5BmWpcMy/Z78 BX6COTlos7H3xvLrnj9B7OIHgExbjF4nI5Oh9zasyZffUD+gg6jL8hM6T3v9Dg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1593518461; 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=qgnrybG2OslXjy+mHoLg62UfvNjCsSTc6swzuIPA9nA=; b=+zw99FP6yn6lVWbVXm8eHgddaRlE6EMcvP7b0alytqiVcGdcVigVWGm0CNaRmPgCGlsiSx sJdE3Mzaks1vxhAw== From: Sebastian Andrzej Siewior To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin " Subject: Re: [PATCH 1/2] x86/entry: Use should_resched() in idtentry_exit_cond_resched() Message-ID: <20200630120059.x5p6uh4hzgqrgwuo@linutronix.de> References: <20200630102209.1143072-1-bigeasy@linutronix.de> <20200630102209.1143072-2-bigeasy@linutronix.de> <20200630111012.GM4800@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200630111012.GM4800@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-06-30 13:10:12 [+0200], Peter Zijlstra wrote: > > --- a/arch/x86/entry/common.c > > +++ b/arch/x86/entry/common.c > > @@ -612,13 +612,12 @@ bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs) > > > > static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched) > > { > > - if (may_sched && !preempt_count()) { > > + if (may_sched && should_resched(0)) { > > /* Sanity check RCU and thread stack */ > > rcu_irq_exit_check_preempt(); > > if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) > > WARN_ON_ONCE(!on_thread_stack()); > > This was done on purpose, your change avoids hitting this WARN. > > The thing is, if we could preempt (but not nessecarily have to) we want > to validate we're on the thread stack. Okay then. Sebastian