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[209.132.180.67]) by mx.google.com with ESMTP id 94si9246733plb.676.2017.07.28.00.09.52; Fri, 28 Jul 2017 00:09:52 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.b=U/qWcW+E; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751620AbdG1HJf (ORCPT + 26 others); Fri, 28 Jul 2017 03:09:35 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:32842 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751045AbdG1HJd (ORCPT ); Fri, 28 Jul 2017 03:09:33 -0400 Received: by mail-pf0-f181.google.com with SMTP id d67so24734508pfc.0 for ; Fri, 28 Jul 2017 00:09:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id; bh=ufjTBYnqOHJ1YIt6BS6p6IUKNrTVPnJqb/tTJmZSUhk=; b=U/qWcW+Em532WVbSsdx2PWu2O8wKnkYK3nWkvFKXDnXOhIYfhP3URbJqTwqgg9m+ex rTv4MK/WpPZGWWIfMsvEq2N6P2NKsSgUbXwzCfGfXvs0Ju6PwSnN9fR2SpQuPLl6bnCT rfLvXaJNHx6FYitTklAq6aT7mzHYsbpMfcenI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=ufjTBYnqOHJ1YIt6BS6p6IUKNrTVPnJqb/tTJmZSUhk=; b=r/CJ7+HLl0A5kMP8XKnuur7hfP+zoBwByYnGAdDsD/6B9RqG5nRdCygOWZv0XOTzcB a3sMd07sGZbdv8u/77X6v51lZUaRfkOeEnZdtCssk2OTu+8bH65VqOiestnrjIqjFgQB EI7QNp8aY26+T7vCfineQ1emZKNPxhfHanPW5b72r9ZLPvSVuibsY16VrI5Mr02uxisc KtOPXsrKAQC2Dz/xFKasMogkP0M9sK6atagv4Q7GJHHuYUMGSRlbhiK/n4kAw4haLgok sJJILIkEuFxAsX8SCAHp1IYd/0+RIuERfXqMJb+JcrrGZ5cmIiJm7y5vfpr35abzVRS0 +12w== X-Gm-Message-State: AIVw111behg/YI8uWhST4h6oY2OVMMmRQIeQHdvAJIHH7lTMWm4vzWE8 pl9EyTYPLikslU0J4Kmvjg== X-Received: by 10.84.129.45 with SMTP id 42mr6987323plb.229.1501225772891; Fri, 28 Jul 2017 00:09:32 -0700 (PDT) Received: from localhost.localdomain ([45.56.152.20]) by smtp.gmail.com with ESMTPSA id u186sm12710887pfu.82.2017.07.28.00.09.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 28 Jul 2017 00:09:31 -0700 (PDT) From: Alex Shi To: rafael@kernel.org, linux-kernel@vger.kernel.org (open list) Cc: Alex Shi , Sebastian Andrzej Siewior , Thomas Gleixner , Anders Roxell , Daniel Lezcano , Tony Lindgren , linux-pm@vger.kernel.org, linux-rt-users Subject: [PATCH] cpu_pm: replace raw_notifier to atomic_notifier Date: Fri, 28 Jul 2017 15:09:25 +0800 Message-Id: <1501225765-16869-1-git-send-email-alex.shi@linaro.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Lindgren 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 Tested-by: Tony Lindgren 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(-) -- 2.7.4 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);