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=-14.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 1FE85C433DF for ; Thu, 27 Aug 2020 07:57:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBD4420825 for ; Thu, 27 Aug 2020 07:57:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="TQB6dctE"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Wl1BNZCE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728710AbgH0H46 (ORCPT ); Thu, 27 Aug 2020 03:56:58 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:36582 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728406AbgH0Hy1 (ORCPT ); Thu, 27 Aug 2020 03:54:27 -0400 Date: Thu, 27 Aug 2020 07:54:24 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1598514865; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w6tcGtJrvRcbQhtixqj4vbfrcEniRUb9RXpR3YqCwCo=; b=TQB6dctEgX0fc8AumrRync/Zakej1MV8+C5SdB3pfIiqbvm9FXGb0p9QXojiHnpHW8kgs7 s9D0mf98P3DDjWTwtaxrTYTl70PEZYBvhAShWuprkGJJXeXVynFhuUyKXE4zt0MFuxiLD/ 79wuAEeezkyjkX+nBPttwGTYUMy7Vm6S5m/C8GKILD4WqTtfygzAonkBxHq0NETsexpZPi bac/bKso9X8/aFQnGTYv7QUzqowWKeWLGKNjq8W+x40cRmElfI4KUdQAF+p0SWXCQJMdcI hNn+SNdCSMocakz/Ch8shNQ7feSiBGfg65xzlZedTUL9VqHfZM5KrF89DcYYMg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1598514865; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w6tcGtJrvRcbQhtixqj4vbfrcEniRUb9RXpR3YqCwCo=; b=Wl1BNZCEH17lXb7fiw6YMVZ+QKNrI6EiUgUned3CXaSaiecJCXQT442N0omRBF5gMGBrOH dpPVpFKbfK+5YPBQ== From: "tip-bot2 for Nicholas Piggin" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] lockdep: Only trace IRQ edges Cc: Nicholas Piggin , "Peter Zijlstra (Intel)" , "Steven Rostedt (VMware)" , Thomas Gleixner , "Rafael J. Wysocki" , Marco Elver , x86 , LKML In-Reply-To: <20200723105615.1268126-1-npiggin@gmail.com> References: <20200723105615.1268126-1-npiggin@gmail.com> MIME-Version: 1.0 Message-ID: <159851486478.20229.13478044751401692917.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the locking/core branch of tip: Commit-ID: 044d0d6de9f50192f9697583504a382347ee95ca Gitweb: https://git.kernel.org/tip/044d0d6de9f50192f9697583504a382347ee95ca Author: Nicholas Piggin AuthorDate: Thu, 23 Jul 2020 20:56:14 +10:00 Committer: Peter Zijlstra CommitterDate: Wed, 26 Aug 2020 12:41:56 +02:00 lockdep: Only trace IRQ edges Problem: raw_local_irq_save(); // software state on local_irq_save(); // software state off ... local_irq_restore(); // software state still off, because we don't enable IRQs raw_local_irq_restore(); // software state still off, *whoopsie* existing instances: - lock_acquire() raw_local_irq_save() __lock_acquire() arch_spin_lock(&graph_lock) pv_wait() := kvm_wait() (same or worse for Xen/HyperV) local_irq_save() - trace_clock_global() raw_local_irq_save() arch_spin_lock() pv_wait() := kvm_wait() local_irq_save() - apic_retrigger_irq() raw_local_irq_save() apic->send_IPI() := default_send_IPI_single_phys() local_irq_save() Possible solutions: A) make it work by enabling the tracing inside raw_*() B) make it work by keeping tracing disabled inside raw_*() C) call it broken and clean it up now Now, given that the only reason to use the raw_* variant is because you don't want tracing. Therefore A) seems like a weird option (although it can be done). C) is tempting, but OTOH it ends up converting a _lot_ of code to raw just because there is one raw user, this strips the validation/tracing off for all the other users. So we pick B) and declare any code that ends up doing: raw_local_irq_save() local_irq_save() lockdep_assert_irqs_disabled(); broken. AFAICT this problem has existed forever, the only reason it came up is because commit: 859d069ee1dd ("lockdep: Prepare for NMI IRQ state tracking") changed IRQ tracing vs lockdep recursion and the first instance is fairly common, the other cases hardly ever happen. Signed-off-by: Nicholas Piggin [rewrote changelog] Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Steven Rostedt (VMware) Reviewed-by: Thomas Gleixner Acked-by: Rafael J. Wysocki Tested-by: Marco Elver Link: https://lkml.kernel.org/r/20200723105615.1268126-1-npiggin@gmail.com --- arch/powerpc/include/asm/hw_irq.h | 11 ++++------- include/linux/irqflags.h | 15 +++++++-------- 2 files changed, 11 insertions(+), 15 deletions(-) diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h index 3a0db7b..35060be 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) #else #define powerpc_local_irq_pmu_save(flags) \ diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 00d553d..3ed4e87 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -191,25 +191,24 @@ do { \ #define local_irq_disable() \ do { \ + bool was_disabled = raw_irqs_disabled();\ raw_local_irq_disable(); \ - trace_hardirqs_off(); \ + if (!was_disabled) \ + trace_hardirqs_off(); \ } while (0) #define local_irq_save(flags) \ do { \ raw_local_irq_save(flags); \ - trace_hardirqs_off(); \ + if (!raw_irqs_disabled_flags(flags)) \ + trace_hardirqs_off(); \ } while (0) #define local_irq_restore(flags) \ do { \ - if (raw_irqs_disabled_flags(flags)) { \ - raw_local_irq_restore(flags); \ - trace_hardirqs_off(); \ - } else { \ + if (!raw_irqs_disabled_flags(flags)) \ trace_hardirqs_on(); \ - raw_local_irq_restore(flags); \ - } \ + raw_local_irq_restore(flags); \ } while (0) #define safe_halt() \