forked from rrcarlosr/Jetpack
185 lines
5.8 KiB
Diff
185 lines
5.8 KiB
Diff
From 19c093806ffb609e2e3a60f62d890c8da3d311c8 Mon Sep 17 00:00:00 2001
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From: Alex Shi <alex.shi@linaro.org>
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Date: Thu, 6 Jul 2017 16:47:46 +0800
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Subject: [PATCH 336/352] cpu_pm: replace raw_notifier to atomic_notifier
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This patch replace a rwlock and raw notifier by atomic notifier which
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protected by spin_lock and rcu.
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The first to reason to have this replace is due to a 'scheduling while
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atomic' bug of RT kernel on arm/arm64 platform. On arm/arm64, rwlock
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cpu_pm_notifier_lock in cpu_pm cause a potential schedule after irq
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disable in idle call chain:
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cpu_startup_entry
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cpu_idle_loop
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local_irq_disable()
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cpuidle_idle_call
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call_cpuidle
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cpuidle_enter
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cpuidle_enter_state
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->enter :arm_enter_idle_state
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cpu_pm_enter/exit
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CPU_PM_CPU_IDLE_ENTER
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read_lock(&cpu_pm_notifier_lock); <-- sleep in idle
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__rt_spin_lock();
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schedule();
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The kernel panic is here:
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[ 4.609601] BUG: scheduling while atomic: swapper/1/0/0x00000002
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[ 4.609608] [<ffff0000086fae70>] arm_enter_idle_state+0x18/0x70
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[ 4.609614] Modules linked in:
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[ 4.609615] [<ffff0000086f9298>] cpuidle_enter_state+0xf0/0x218
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[ 4.609620] [<ffff0000086f93f8>] cpuidle_enter+0x18/0x20
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[ 4.609626] Preemption disabled at:
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[ 4.609627] [<ffff0000080fa234>] call_cpuidle+0x24/0x40
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[ 4.609635] [<ffff000008882fa4>] schedule_preempt_disabled+0x1c/0x28
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[ 4.609639] [<ffff0000080fa49c>] cpu_startup_entry+0x154/0x1f8
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[ 4.609645] [<ffff00000808e004>] secondary_start_kernel+0x15c/0x1a0
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Daniel Lezcano said this notification is needed on arm/arm64 platforms.
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Sebastian suggested using atomic_notifier instead of rwlock, which is not
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only removing the sleeping in idle, but also getting better latency
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improvement.
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This patch passed Fengguang's 0day testing.
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Signed-off-by: Alex Shi <alex.shi@linaro.org>
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Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: Anders Roxell <anders.roxell@linaro.org>
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Cc: Rik van Riel <riel@redhat.com>
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Cc: Steven Rostedt <rostedt@goodmis.org>
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Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
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Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/cpu_pm.c | 47 ++++++-----------------------------------------
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1 file changed, 6 insertions(+), 41 deletions(-)
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diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
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index b14df91..10f4640 100644
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--- a/kernel/cpu_pm.c
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+++ b/kernel/cpu_pm.c
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@@ -22,14 +22,13 @@
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#include <linux/spinlock.h>
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#include <linux/syscore_ops.h>
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-static DEFINE_RAW_SPINLOCK(cpu_pm_notifier_lock);
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-static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
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+static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
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static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
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{
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int ret;
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- ret = __raw_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
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+ ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
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nr_to_call, nr_calls);
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return notifier_to_errno(ret);
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@@ -47,14 +46,7 @@ static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
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*/
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int cpu_pm_register_notifier(struct notifier_block *nb)
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{
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- unsigned long flags;
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- int ret;
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-
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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- ret = raw_notifier_chain_register(&cpu_pm_notifier_chain, nb);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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-
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- return ret;
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+ return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb);
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}
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EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
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@@ -69,14 +61,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
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*/
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int cpu_pm_unregister_notifier(struct notifier_block *nb)
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{
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- unsigned long flags;
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- int ret;
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-
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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- ret = raw_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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-
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- return ret;
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+ return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
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}
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EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
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@@ -99,9 +84,7 @@ int cpu_pm_enter(void)
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{
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int nr_calls;
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int ret = 0;
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- unsigned long flags;
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
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if (ret)
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/*
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@@ -109,7 +92,6 @@ int cpu_pm_enter(void)
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* PM entry who are notified earlier to prepare for it.
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*/
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cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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return ret;
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}
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@@ -129,14 +111,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
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*/
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int cpu_pm_exit(void)
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{
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- int ret;
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- unsigned long flags;
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-
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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- ret = cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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-
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- return ret;
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+ return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(cpu_pm_exit);
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@@ -160,9 +135,7 @@ int cpu_cluster_pm_enter(void)
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{
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int nr_calls;
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int ret = 0;
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- unsigned long flags;
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
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if (ret)
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/*
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@@ -170,7 +143,6 @@ int cpu_cluster_pm_enter(void)
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* PM entry who are notified earlier to prepare for it.
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*/
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cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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return ret;
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}
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@@ -193,14 +165,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
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*/
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int cpu_cluster_pm_exit(void)
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{
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- int ret;
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- unsigned long flags;
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-
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- raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
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- ret = cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
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- raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
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-
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- return ret;
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+ return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
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--
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2.7.4
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