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=-7.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 757F5C433E4 for ; Thu, 23 Jul 2020 13:11:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 547F320737 for ; Thu, 23 Jul 2020 13:11:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VHCvV4tD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728968AbgGWNLK (ORCPT ); Thu, 23 Jul 2020 09:11:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37164 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727859AbgGWNLK (ORCPT ); Thu, 23 Jul 2020 09:11:10 -0400 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C9F4C0619DC; Thu, 23 Jul 2020 06:11:10 -0700 (PDT) Received: by mail-pj1-x1044.google.com with SMTP id gc9so3148941pjb.2; Thu, 23 Jul 2020 06:11:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :message-id:content-transfer-encoding; bh=E/e6bkQ7xor2tf39B3HoCRN8UgDNduwN1Zl5yinxqAQ=; b=VHCvV4tDO0Bo5lG2Zc4hPcBRi5ULljYg08PlC0vzAhBt1p+CAjOX0WO/MyIX6FT/Xz AVXqfD1jopjxBj0S7kL4mgO5TWFgxhWjIwgiNW/HnU1AXeN9Wa9A/R9UWkrrkJZDEl9A Y4GRXVfQdi2aBc5if6fb1s/fm8E43m7KFrJmOZ5D4lLx1neR//DLIeK5TXy+RMVs9mWL zXyf0bGiSKnAjEfPXF02FACc0rMk0Ikkzot//SenWG4yCVgqJ4UgWgE4sRgiS6gbaRIH maTuWUdkFpnk4sPb5nhbOtEDUUMLgvXitYsyqxIZqPsm2ZMlXRIHbfw+ZRcAv2LRAGjV wLfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:message-id:content-transfer-encoding; bh=E/e6bkQ7xor2tf39B3HoCRN8UgDNduwN1Zl5yinxqAQ=; b=NEvO9CeaUnSEZ+hDUG4eF6pvVN7c0ts44PCupbUm1bYVFYjHFL+YsFBs0AHWS8UWJu loObe8hhl2pYlStSrxERDRluP8smrjVDwS/sZrYdHIeyHZuR1TAqp/QoFfPx9ETxxnih 2NDot1AOlN0rj16dfX87zklXfd39dI1BfjrjhkhgJKryD88qyGGAgvg9Bxw15nc0iU94 u3wrEDXAM+dJzb1v/5CxBntNMsfhgbJjocxwmVpgZgpMlzcVE6aA6peHaMjfuRXSq3Uh oe5/lJb4qLWSE/hWQid7T0E2y36mvufV33RH7WdYcgJZWLKv/zj0RKFDaEEF264IUKql L5Jg== X-Gm-Message-State: AOAM5336AMSISRXHwZi/JXahnDtrJX3FM6T8r3W4fFolix7gJJi6jzTs UqeY2Hda2j9t+1fZzqJwkp0= X-Google-Smtp-Source: ABdhPJzyDRqU0+pKFo017avcsBGjeFT0wLcR3XwTdTSuoYbBl6djhiXCSDZYxDgTPpeRhvXDAsKYsw== X-Received: by 2002:a17:90a:6b02:: with SMTP id v2mr310422pjj.163.1595509869825; Thu, 23 Jul 2020 06:11:09 -0700 (PDT) Received: from localhost (110-174-173-27.tpgi.com.au. [110.174.173.27]) by smtp.gmail.com with ESMTPSA id g18sm3001623pfi.141.2020.07.23.06.11.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2020 06:11:09 -0700 (PDT) Date: Thu, 23 Jul 2020 23:11:03 +1000 From: Nicholas Piggin Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state To: Peter Zijlstra Cc: Alexey Kardashevskiy , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Will Deacon References: <20200723105615.1268126-1-npiggin@gmail.com> <20200723114010.GO5523@worktop.programming.kicks-ass.net> In-Reply-To: <20200723114010.GO5523@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Message-Id: <1595506730.3mvrxktem5.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Peter Zijlstra's message of July 23, 2020 9:40 pm: > On Thu, Jul 23, 2020 at 08:56:14PM +1000, Nicholas Piggin wrote: >=20 >> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/as= m/hw_irq.h >> index 3a0db7b0b46e..35060be09073 100644 >> --- a/arch/powerpc/include/asm/hw_irq.h >> +++ b/arch/powerpc/include/asm/hw_irq.h >> @@ -200,17 +200,14 @@ static inline bool arch_irqs_disabled(void) >> #define powerpc_local_irq_pmu_save(flags) \ >> do { \ >> raw_local_irq_pmu_save(flags); \ >> - trace_hardirqs_off(); \ >> + if (!raw_irqs_disabled_flags(flags)) \ >> + trace_hardirqs_off(); \ >> } while(0) >> #define powerpc_local_irq_pmu_restore(flags) \ >> do { \ >> - if (raw_irqs_disabled_flags(flags)) { \ >> - raw_local_irq_pmu_restore(flags); \ >> - trace_hardirqs_off(); \ >> - } else { \ >> + if (!raw_irqs_disabled_flags(flags)) \ >> trace_hardirqs_on(); \ >> - raw_local_irq_pmu_restore(flags); \ >> - } \ >> + raw_local_irq_pmu_restore(flags); \ >> } while(0) >=20 > You shouldn't be calling lockdep from NMI context! After this patch it doesn't. trace_hardirqs_on/off implementation appears to expect to be called in NMI=20 context though, for some reason. > That is, I recently > added suport for that on x86: >=20 > https://lkml.kernel.org/r/20200623083721.155449112@infradead.org > https://lkml.kernel.org/r/20200623083721.216740948@infradead.org >=20 > But you need to be very careful on how you order things, as you can see > the above relies on preempt_count() already having been incremented with > NMI_MASK. Hmm. My patch seems simpler. I don't know this stuff very well, I don't really understand what your patc= h=20 enables for x86 but at least it shouldn't be incompatible with this one=20 AFAIKS. Thanks, Nick