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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 E17D8C433E3 for ; Wed, 19 Aug 2020 15:40:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA36E207FF for ; Wed, 19 Aug 2020 15:40:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="iM2jo4Vk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728825AbgHSPj7 (ORCPT ); Wed, 19 Aug 2020 11:39:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726894AbgHSPj5 (ORCPT ); Wed, 19 Aug 2020 11:39:57 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0B7EC061757; Wed, 19 Aug 2020 08:39:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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=A/NLDEqSKQO5M1WQObNymH18o4NlNdxjll2by5D8bbE=; b=iM2jo4Vkp8b1Brl9BuejvbdL4q uyEe0Iygv7v92s+Gs5XNITaVQMbU+ie4eWP1lPmZsJroegcnyl5wqfRGY1bweEH1cH+NLqkOhjCs7 ihL+pVwi1DffiQyKENwc0G2/7+6VUVt5ihMWefbrvGSks18PYeyBXSM6XXdsiToUhza/SifSRn9/K 65swPPEhRGGab8qDuBogNkb76IGW313uWwSetAhxG+WPw0EdnM1WMQ8ghH6zi1Pc/Xyj7HlEUY+8I hFV7ER+hErZgX+VFmlgEENeHALwZlA7S1SKEH3ew1MtMkOMme5SS7h745f//FCWrV6v2qnY89unTQ YCHyzPRQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k8QBr-0007p3-8U; Wed, 19 Aug 2020 15:39:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7BACF3059C6; Wed, 19 Aug 2020 17:39:49 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5FEE82BEB7F3D; Wed, 19 Aug 2020 17:39:49 +0200 (CEST) Date: Wed, 19 Aug 2020 17:39:49 +0200 From: peterz@infradead.org To: Alexey Kardashevskiy Cc: Nicholas Piggin , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Will Deacon Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Message-ID: <20200819153949.GO35926@hirez.programming.kicks-ass.net> References: <20200723105615.1268126-1-npiggin@gmail.com> <20200807111126.GI2674@hirez.programming.kicks-ass.net> <1597220073.mbvcty6ghk.astroid@bobo.none> <20200812103530.GL2674@hirez.programming.kicks-ass.net> <1597735273.s0usqkrlsk.astroid@bobo.none> <20200818154143.GT2674@hirez.programming.kicks-ass.net> <1597793862.l8c4pmmzpq.astroid@bobo.none> <7fadb5ab-9869-396d-ff5d-c0adb6fc0b35@ozlabs.ru> <20200819153250.GF2674@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200819153250.GF2674@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 Wed, Aug 19, 2020 at 05:32:50PM +0200, peterz@infradead.org wrote: > On Wed, Aug 19, 2020 at 08:39:13PM +1000, Alexey Kardashevskiy wrote: > > > > or current upstream? > > > > The upstream 18445bf405cb (13 hours old) also shows the problem. Yours > > 1/2 still fixes it. > > Afaict that just reduces the window. > > Isn't the problem that: > > arch/powerpc/kernel/exceptions-64e.S > > START_EXCEPTION(perfmon); > NORMAL_EXCEPTION_PROLOG(0x260, BOOKE_INTERRUPT_PERFORMANCE_MONITOR, > PROLOG_ADDITION_NONE) > EXCEPTION_COMMON(0x260) > INTS_DISABLE > # RECONCILE_IRQ_STATE > # TRACE_DISABLE_INTS > # TRACE_WITH_FRAME_BUFFER(trace_hardirqs_off) > # > # but we haven't done nmi_enter() yet... whoopsy > > CHECK_NAPPING() > addi r3,r1,STACK_FRAME_OVERHEAD > bl performance_monitor_exception > # perf_irq() > # perf_event_interrupt > # __perf_event_interrupt > # nmi_enter() > > > > That is, afaict your entry code is buggered. That is, patch 1/2 doesn't change the case: local_irq_enable() trace_hardirqs_on() trace_hardirqs_off() ... if (regs_irqs_disabled(regs)) // false trace_hardirqs_on(); raw_local_irq_enable() Where local_irq_enable() has done trace_hardirqs_on() and the NMI hits and undoes it, but doesn't re-do it because the hardware state is still disabled. What's supposed to happen is: nmi_enter() trace_hardirqs_off() // no-op, because in_nmi() (or previously because lockdep_off()) ...