From patchwork Sun Jul 16 23:24:11 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alex Shi X-Patchwork-Id: 9843761 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id DAD8960393 for ; Sun, 16 Jul 2017 23:24:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BC2AB26E55 for ; Sun, 16 Jul 2017 23:24:29 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9CAC627F98; Sun, 16 Jul 2017 23:24:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_HI, URIBL_ABUSE_SURBL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D75A426E55 for ; Sun, 16 Jul 2017 23:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751221AbdGPXYW (ORCPT ); Sun, 16 Jul 2017 19:24:22 -0400 Received: from mail-pf0-f175.google.com ([209.85.192.175]:35994 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbdGPXYV (ORCPT ); Sun, 16 Jul 2017 19:24:21 -0400 Received: by mail-pf0-f175.google.com with SMTP id q86so67886539pfl.3 for ; Sun, 16 Jul 2017 16:24:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=YMarBE/k7pj3hJCzeGAFzeRJCihblmRKM+gjoksFUnU=; b=j6Fnq6I5Mu2EjQUlpb/HzqTEExPhKL3lTgHlvxsMiVWrxpAMSXiNbm/tfjH3WgC4yY mU8PH76ZrqpdMNQ7OEWBfsmb7Hg17cedd/agukbTN7yzJJo0tmAuyoaUBOSiXLPJmP75 QI4/va3MmY0+vjKCYNNUkB5fMdKJYcDNpzqi8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=YMarBE/k7pj3hJCzeGAFzeRJCihblmRKM+gjoksFUnU=; b=ej53TrBUy/X+EbnUxhw8pOoVbs6lnwpiU9caI6afMB214QgMe0C26d5BWENZdP8puf A0FHhHalPF+zKAUwVpBe57lsygnddhlE23/uPqky5+XXki2tvuNs5Ach434KCfWHOYU2 5khmH1roEKKCjzyHPoUDGVyzIzFzaNE8Y/JKI+wAIbpHOd4yxNl9u3eOn4ykOL2azmCs TWEvrpEfX3Vga1VJS+GdKOYpUQlybY9YJc9Fi0tHjEU61pNXzHZgKqA4CCOsFtUHqEG3 NC1xiOd9Nn+kByEFuDGzoKYGVsCUYEe90n4wzr1j/WqFYZrzEFjQQtVyXR+VxbjY3Kx8 0MIQ== X-Gm-Message-State: AIVw113MkjdyDMHZey3VPgPE4oW7DzGQLIPCt5FmcH08733fsFF/jx2O UamtR1X1v9JzCa5o X-Received: by 10.84.224.15 with SMTP id r15mr26908010plj.78.1500247460927; Sun, 16 Jul 2017 16:24:20 -0700 (PDT) Received: from [192.168.1.113] ([180.127.208.187]) by smtp.gmail.com with ESMTPSA id w87sm31850735pfk.100.2017.07.16.16.24.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 16 Jul 2017 16:24:19 -0700 (PDT) Subject: Re: Regression with suspicious RCU usage splats with cpu_pm change To: paulmck@linux.vnet.ibm.com, "Rafael J. Wysocki" Cc: Tony Lindgren , Linux Kernel Mailing List , Linux PM , Linux OMAP Mailing List , Catalin Marinas , Will Deacon References: <20170713070749.GE16509@atomide.com> <20170713124318.GK2393@linux.vnet.ibm.com> From: Alex Shi Message-ID: Date: Mon, 17 Jul 2017 07:24:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170713124318.GK2393@linux.vnet.ibm.com> Content-Language: en-US Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On 07/13/2017 08:43 PM, Paul E. McKenney wrote: > On Thu, Jul 13, 2017 at 01:50:26PM +0200, Rafael J. Wysocki wrote: >> On Thu, Jul 13, 2017 at 11:43 AM, Alex Shi wrote: >>> >>> On 07/13/2017 03:07 PM, Tony Lindgren wrote: >>>> Hi, >>>> >>>> Looks like next-20170713 gives me a bunch of "suspicious RCU usage" >>>> splats with cpuidle_coupled on duovero, see below. I bisected it down >>>> to commit 2f027e003d05 ("cpu_pm: replace raw_notifier with >>>> atomic_notifier"). >> >> OK, so I'm dropping this commit. > > You can surround idle-loop RCU-reading code with RCU_NONIDLE(). > This will tell RCU to pay attention even though the CPU is otherwise > idle. > > Thanx, Paul > Thanks a lot, Paul! :) I reused the rcu_irq_enter_irqson() from RCU_NONIDLE to avoid this issue. It works fine. Tony, Could you like to give a tested-by if this patch works for you. Sebastian, May I keep your acked-by with new fixed patch, since the main thing remained? :) Thanks everyone! Tested-by: Tony Lindgren Tested-by: Tony Lindgren ====== From c8ec81808d46a78e58267f6a23f2b58b48ed5725 Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Tue, 4 Jul 2017 21:49:23 +0800 Subject: [PATCH] cpu_pm: replace raw_notifier to atomic_notifier This patch replace a rwlock and raw notifier by atomic notifier which protected by spin_lock and rcu. The first to reason to have this replace is due to a 'scheduling while atomic' bug of RT kernel on arm/arm64 platform. On arm/arm64, rwlock cpu_pm_notifier_lock in cpu_pm cause a potential schedule after irq disable in idle call chain: cpu_startup_entry cpu_idle_loop local_irq_disable() cpuidle_idle_call call_cpuidle cpuidle_enter cpuidle_enter_state ->enter :arm_enter_idle_state cpu_pm_enter/exit CPU_PM_CPU_IDLE_ENTER read_lock(&cpu_pm_notifier_lock); <-- sleep in idle __rt_spin_lock(); schedule(); The kernel panic is here: [ 4.609601] BUG: scheduling while atomic: swapper/1/0/0x00000002 [ 4.609608] [] arm_enter_idle_state+0x18/0x70 [ 4.609614] Modules linked in: [ 4.609615] [] cpuidle_enter_state+0xf0/0x218 [ 4.609620] [] cpuidle_enter+0x18/0x20 [ 4.609626] Preemption disabled at: [ 4.609627] [] call_cpuidle+0x24/0x40 [ 4.609635] [] schedule_preempt_disabled+0x1c/0x28 [ 4.609639] [] cpu_startup_entry+0x154/0x1f8 [ 4.609645] [] secondary_start_kernel+0x15c/0x1a0 Daniel Lezcano said this notification is needed on arm/arm64 platforms. Sebastian suggested using atomic_notifier instead of rwlock, which is not only removing the sleeping in idle, but also getting better latency improvement. Tony Lezcano found a miss use that rcu_read_lock used after rcu_idle_enter Paul E. McKenney suggested trying RCU_NONIDLE. Thanks everyone! :) This patch passed Fengguang's 0day testing. Signed-off-by: Alex Shi To: linux-kernel@vger.kernel.org Cc: Sebastian Andrzej Siewior Cc: Thomas Gleixner Cc: Anders Roxell Cc: Daniel Lezcano Cc: Rafael J. Wysocki Cc: Tony Lindgren Cc: linux-pm@vger.kernel.org Cc: linux-rt-users Acked-by: Sebastian Andrzej Siewior --- kernel/cpu_pm.c | 50 +++++++++++++------------------------------------- 1 file changed, 13 insertions(+), 37 deletions(-) diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c index 009cc9a..67b02e1 100644 --- a/kernel/cpu_pm.c +++ b/kernel/cpu_pm.c @@ -22,15 +22,21 @@ #include #include -static DEFINE_RWLOCK(cpu_pm_notifier_lock); -static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain); +static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain); static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls) { int ret; - ret = __raw_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL, + /* + * __atomic_notifier_call_chain has a RCU read critical section, which + * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let + * RCU know this. + */ + rcu_irq_enter_irqson(); + ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL, nr_to_call, nr_calls); + rcu_irq_exit_irqson(); return notifier_to_errno(ret); } @@ -47,14 +53,7 @@ static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls) */ int cpu_pm_register_notifier(struct notifier_block *nb) { - unsigned long flags; - int ret; - - write_lock_irqsave(&cpu_pm_notifier_lock, flags); - ret = raw_notifier_chain_register(&cpu_pm_notifier_chain, nb); - write_unlock_irqrestore(&cpu_pm_notifier_lock, flags); - - return ret; + return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb); } EXPORT_SYMBOL_GPL(cpu_pm_register_notifier); @@ -69,14 +68,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_register_notifier); */ int cpu_pm_unregister_notifier(struct notifier_block *nb) { - unsigned long flags; - int ret; - - write_lock_irqsave(&cpu_pm_notifier_lock, flags); - ret = raw_notifier_chain_unregister(&cpu_pm_notifier_chain, nb); - write_unlock_irqrestore(&cpu_pm_notifier_lock, flags); - - return ret; + return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb); } EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier); @@ -100,7 +92,6 @@ int cpu_pm_enter(void) int nr_calls; int ret = 0; - read_lock(&cpu_pm_notifier_lock); ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls); if (ret) /* @@ -108,7 +99,6 @@ int cpu_pm_enter(void) * PM entry who are notified earlier to prepare for it. */ cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL); - read_unlock(&cpu_pm_notifier_lock); return ret; } @@ -128,13 +118,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter); */ int cpu_pm_exit(void) { - int ret; - - read_lock(&cpu_pm_notifier_lock); - ret = cpu_pm_notify(CPU_PM_EXIT, -1, NULL); - read_unlock(&cpu_pm_notifier_lock); - - return ret; + return cpu_pm_notify(CPU_PM_EXIT, -1, NULL); } EXPORT_SYMBOL_GPL(cpu_pm_exit); @@ -159,7 +143,6 @@ int cpu_cluster_pm_enter(void) int nr_calls; int ret = 0; - read_lock(&cpu_pm_notifier_lock); ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls); if (ret) /* @@ -167,7 +150,6 @@ int cpu_cluster_pm_enter(void) * PM entry who are notified earlier to prepare for it. */ cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL); - read_unlock(&cpu_pm_notifier_lock); return ret; } @@ -190,13 +172,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter); */ int cpu_cluster_pm_exit(void) { - int ret; - - read_lock(&cpu_pm_notifier_lock); - ret = cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL); - read_unlock(&cpu_pm_notifier_lock); - - return ret; + return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL); } EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);