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[209.132.180.67]) by mx.google.com with ESMTP id s6si688340plj.156.2017.07.11.17.49.11; Tue, 11 Jul 2017 17:49:12 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-pm-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=Af9qwjzR; spf=pass (google.com: best guess record for domain of linux-pm-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-pm-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 S932655AbdGLAtK (ORCPT + 14 others); Tue, 11 Jul 2017 20:49:10 -0400 Received: from mail-pf0-f177.google.com ([209.85.192.177]:36824 "EHLO mail-pf0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932365AbdGLAtJ (ORCPT ); Tue, 11 Jul 2017 20:49:09 -0400 Received: by mail-pf0-f177.google.com with SMTP id q86so4123098pfl.3 for ; Tue, 11 Jul 2017 17:49:09 -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=CQFX9VbWHg9k7EJBCpdpTh+x9btYLfo6k57TVGtQpjs=; b=Af9qwjzRG0zmLQcTNk0ADErS/Yt4uZoz2eUX8QUTnHqKaG1nR6vNXGK4CyK3kSOTcG G2EVtpyuZZfR9o4H0SF9tIcs7StrrykQxkUW7gGUaDOjAaRXUjUwnlCX1DTIdjrZcjnf XrOkIKWe9m6QSNh/Zwn7PjKrrBll7jR0/ENKU= 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=CQFX9VbWHg9k7EJBCpdpTh+x9btYLfo6k57TVGtQpjs=; b=AA44fkv+Ze7Hm7H5sZLgw7FP6qETIzsGY4MM1hO1WCy6QasMYgGNBtCxpYUPse6z9O gd3PGivO22lNoSWKILtWT18GctuAmF6CsHfHMV6UmrdSy7vqplSiFkQa19f359NSPMdf mJeLbJ0dvVYaEJPUXbOJY+fot+tw1chYVU8w/rSrKmHEdxXs0ojnp2TeBHNX1g8Goaks xLs7DXB/qfqA7+A3092GWZUslqz2SfzQ0OFbyoSKnyqnjEOE8NcSSh3C9/ZdpqvBYCYH rBmmY7qxPHYoDuJRuLILG+XBbT8qQn25faSqKgevr/xGOiHNYN0mKBnKQvSoZNH9YR4b RPmg== X-Gm-Message-State: AIVw112+DGYXI9J0nLnzWJjQhnhkeYeSKOl6MKhAfLK6IMkeQRv+AqSj TNDKDxnUqnfI4vUz X-Received: by 10.84.233.204 with SMTP id m12mr1254075pln.292.1499820548798; Tue, 11 Jul 2017 17:49:08 -0700 (PDT) Received: from localhost.localdomain ([104.237.91.191]) by smtp.gmail.com with ESMTPSA id v205sm808708pgb.51.2017.07.11.17.49.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 11 Jul 2017 17:49:07 -0700 (PDT) From: Alex Shi To: linux-kernel@vger.kernel.org (open list) Cc: Alex Shi , Sebastian Andrzej Siewior , Thomas Gleixner , Anders Roxell , Daniel Lezcano , linux-rt-users , linux-pm@vger.kernel.org Subject: [PATCH] cpu_pm: replace raw_notifier to atomic_notifier Date: Wed, 12 Jul 2017 08:48:18 +0800 Message-Id: <1499820498-7983-1-git-send-email-alex.shi@linaro.org> X-Mailer: git-send-email 2.7.4 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@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. 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: linux-rt-users Cc: linux-pm@vger.kernel.org Acked-by: Sebastian Andrzej Siewior --- kernel/cpu_pm.c | 43 ++++++------------------------------------- 1 file changed, 6 insertions(+), 37 deletions(-) -- 2.7.4 diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c index 009cc9a..10f4640 100644 --- a/kernel/cpu_pm.c +++ b/kernel/cpu_pm.c @@ -22,14 +22,13 @@ #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, + ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL, nr_to_call, nr_calls); return notifier_to_errno(ret); @@ -47,14 +46,7 @@ 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 +61,7 @@ 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 +85,6 @@ 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 +92,6 @@ 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 +111,7 @@ 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 +136,6 @@ 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 +143,6 @@ 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 +165,7 @@ 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);