tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Fast batching percpu counters.
3 */
4
5#include <linux/percpu_counter.h>
6#include <linux/notifier.h>
7#include <linux/mutex.h>
8#include <linux/init.h>
9#include <linux/cpu.h>
10#include <linux/module.h>
11
12#ifdef CONFIG_HOTPLUG_CPU
13static LIST_HEAD(percpu_counters);
14static DEFINE_MUTEX(percpu_counters_lock);
15#endif
16
17void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
18{
19 int cpu;
20
21 spin_lock(&fbc->lock);
22 for_each_possible_cpu(cpu) {
23 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
24 *pcount = 0;
25 }
26 fbc->count = amount;
27 spin_unlock(&fbc->lock);
28}
29EXPORT_SYMBOL(percpu_counter_set);
30
31void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
32{
33 s64 count;
34 s32 *pcount;
35 int cpu = get_cpu();
36
37 pcount = per_cpu_ptr(fbc->counters, cpu);
38 count = *pcount + amount;
39 if (count >= batch || count <= -batch) {
40 spin_lock(&fbc->lock);
41 fbc->count += count;
42 *pcount = 0;
43 spin_unlock(&fbc->lock);
44 } else {
45 *pcount = count;
46 }
47 put_cpu();
48}
49EXPORT_SYMBOL(__percpu_counter_add);
50
51/*
52 * Add up all the per-cpu counts, return the result. This is a more accurate
53 * but much slower version of percpu_counter_read_positive()
54 */
55s64 __percpu_counter_sum(struct percpu_counter *fbc)
56{
57 s64 ret;
58 int cpu;
59
60 spin_lock(&fbc->lock);
61 ret = fbc->count;
62 for_each_online_cpu(cpu) {
63 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
64 ret += *pcount;
65 }
66 spin_unlock(&fbc->lock);
67 return ret;
68}
69EXPORT_SYMBOL(__percpu_counter_sum);
70
71static struct lock_class_key percpu_counter_irqsafe;
72
73int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
74{
75 spin_lock_init(&fbc->lock);
76 fbc->count = amount;
77 fbc->counters = alloc_percpu(s32);
78 if (!fbc->counters)
79 return -ENOMEM;
80#ifdef CONFIG_HOTPLUG_CPU
81 mutex_lock(&percpu_counters_lock);
82 list_add(&fbc->list, &percpu_counters);
83 mutex_unlock(&percpu_counters_lock);
84#endif
85 return 0;
86}
87EXPORT_SYMBOL(percpu_counter_init);
88
89int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
90{
91 int err;
92
93 err = percpu_counter_init(fbc, amount);
94 if (!err)
95 lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
96 return err;
97}
98
99void percpu_counter_destroy(struct percpu_counter *fbc)
100{
101 if (!fbc->counters)
102 return;
103
104 free_percpu(fbc->counters);
105 fbc->counters = NULL;
106#ifdef CONFIG_HOTPLUG_CPU
107 mutex_lock(&percpu_counters_lock);
108 list_del(&fbc->list);
109 mutex_unlock(&percpu_counters_lock);
110#endif
111}
112EXPORT_SYMBOL(percpu_counter_destroy);
113
114#ifdef CONFIG_HOTPLUG_CPU
115static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
116 unsigned long action, void *hcpu)
117{
118 unsigned int cpu;
119 struct percpu_counter *fbc;
120
121 if (action != CPU_DEAD)
122 return NOTIFY_OK;
123
124 cpu = (unsigned long)hcpu;
125 mutex_lock(&percpu_counters_lock);
126 list_for_each_entry(fbc, &percpu_counters, list) {
127 s32 *pcount;
128 unsigned long flags;
129
130 spin_lock_irqsave(&fbc->lock, flags);
131 pcount = per_cpu_ptr(fbc->counters, cpu);
132 fbc->count += *pcount;
133 *pcount = 0;
134 spin_unlock_irqrestore(&fbc->lock, flags);
135 }
136 mutex_unlock(&percpu_counters_lock);
137 return NOTIFY_OK;
138}
139
140static int __init percpu_counter_startup(void)
141{
142 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
143 return 0;
144}
145module_init(percpu_counter_startup);
146#endif