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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c 
 kernel/kernel/cpu_pm.c
....@@ -1,18 +1,9 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * Copyright (C) 2011 Google, Inc.
34  *
45  * Author:
56  *	Colin Cross <ccross@android.com>
6
- *
7
- * This software is licensed under the terms of the GNU General Public
8
- * License version 2, as published by the Free Software Foundation, and
9
- * may be copied, distributed, and modified under those terms.
10
- *
11
- * This program is distributed in the hope that it will be useful,
12
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
13
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14
- * GNU General Public License for more details.
15
- *
167  */
178 
189 #include <linux/kernel.h>
....@@ -22,20 +13,46 @@
2213 #include <linux/spinlock.h>
2314 #include <linux/syscore_ops.h>
2415 
25
-static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
16
+/*
17
+ * atomic_notifiers use a spinlock_t, which can block under PREEMPT_RT.
18
+ * Notifications for cpu_pm will be issued by the idle task itself, which can
19
+ * never block, IOW it requires using a raw_spinlock_t.
20
+ */
21
+static struct {
22
+	struct raw_notifier_head chain;
23
+	raw_spinlock_t lock;
24
+} cpu_pm_notifier = {
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+	.chain = RAW_NOTIFIER_INIT(cpu_pm_notifier.chain),
26
+	.lock  = __RAW_SPIN_LOCK_UNLOCKED(cpu_pm_notifier.lock),
27
+};
2628 
27
-static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
29
+static int cpu_pm_notify(enum cpu_pm_event event)
2830 {
2931 	int ret;
3032 
3133 	/*
32
-	 * __atomic_notifier_call_chain has a RCU read critical section, which
33
-	 * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
34
-	 * RCU know this.
34
+	 * This introduces a RCU read critical section, which could be
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+	 * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
36
+	 * this.
3537 	 */
3638 	rcu_irq_enter_irqson();
37
-	ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
38
-		nr_to_call, nr_calls);
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+	rcu_read_lock();
40
+	ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
41
+	rcu_read_unlock();
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+	rcu_irq_exit_irqson();
43
+
44
+	return notifier_to_errno(ret);
45
+}
46
+
47
+static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
48
+{
49
+	unsigned long flags;
50
+	int ret;
51
+
52
+	rcu_irq_enter_irqson();
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+	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
54
+	ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
55
+	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
3956 	rcu_irq_exit_irqson();
4057 
4158 	return notifier_to_errno(ret);
....@@ -48,12 +65,17 @@
4865  * Add a driver to a list of drivers that are notified about
4966  * CPU and CPU cluster low power entry and exit.
5067  *
51
- * This function may sleep, and has the same return conditions as
52
- * raw_notifier_chain_register.
68
+ * This function has the same return conditions as raw_notifier_chain_register.
5369  */
5470 int cpu_pm_register_notifier(struct notifier_block *nb)
5571 {
56
-	return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb);
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+	unsigned long flags;
73
+	int ret;
74
+
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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);
78
+	return ret;
5779 }
5880 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
5981 
....@@ -63,12 +85,17 @@
6385  *
6486  * Remove a driver from the CPU PM notifier list.
6587  *
66
- * This function may sleep, and has the same return conditions as
67
- * raw_notifier_chain_unregister.
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+ * This function has the same return conditions as raw_notifier_chain_unregister.
6889  */
6990 int cpu_pm_unregister_notifier(struct notifier_block *nb)
7091 {
71
-	return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
92
+	unsigned long flags;
93
+	int ret;
94
+
95
+	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
96
+	ret = raw_notifier_chain_unregister(&cpu_pm_notifier.chain, nb);
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+	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
98
+	return ret;
7299 }
73100 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
74101 
....@@ -89,18 +116,7 @@
89116  */
90117 int cpu_pm_enter(void)
91118 {
92
-	int nr_calls = 0;
93
-	int ret = 0;
94
-
95
-	ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
96
-	if (ret)
97
-		/*
98
-		 * Inform listeners (nr_calls - 1) about failure of CPU PM
99
-		 * PM entry who are notified earlier to prepare for it.
100
-		 */
101
-		cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
102
-
103
-	return ret;
119
+	return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
104120 }
105121 EXPORT_SYMBOL_GPL(cpu_pm_enter);
106122 
....@@ -118,7 +134,7 @@
118134  */
119135 int cpu_pm_exit(void)
120136 {
121
-	return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
137
+	return cpu_pm_notify(CPU_PM_EXIT);
122138 }
123139 EXPORT_SYMBOL_GPL(cpu_pm_exit);
124140 
....@@ -140,18 +156,7 @@
140156  */
141157 int cpu_cluster_pm_enter(void)
142158 {
143
-	int nr_calls = 0;
144
-	int ret = 0;
145
-
146
-	ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
147
-	if (ret)
148
-		/*
149
-		 * Inform listeners (nr_calls - 1) about failure of CPU cluster
150
-		 * PM entry who are notified earlier to prepare for it.
151
-		 */
152
-		cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
153
-
154
-	return ret;
159
+	return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
155160 }
156161 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
157162 
....@@ -172,7 +177,7 @@
172177  */
173178 int cpu_cluster_pm_exit(void)
174179 {
175
-	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
180
+	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
176181 }
177182 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
178183