locking, percpu counters: introduce separate lock classes
[linux-3.10.git] / lib / percpu_counter.c
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
13 static LIST_HEAD(percpu_counters);
14 static DEFINE_MUTEX(percpu_counters_lock);
15 #endif
16
17 void 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 }
29 EXPORT_SYMBOL(percpu_counter_set);
30
31 void __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 }
49 EXPORT_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  */
55 s64 __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                 *pcount = 0;
66         }
67         fbc->count = ret;
68
69         spin_unlock(&fbc->lock);
70         return ret;
71 }
72 EXPORT_SYMBOL(__percpu_counter_sum);
73
74 int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
75                           struct lock_class_key *key)
76 {
77         spin_lock_init(&fbc->lock);
78         lockdep_set_class(&fbc->lock, key);
79         fbc->count = amount;
80         fbc->counters = alloc_percpu(s32);
81         if (!fbc->counters)
82                 return -ENOMEM;
83 #ifdef CONFIG_HOTPLUG_CPU
84         mutex_lock(&percpu_counters_lock);
85         list_add(&fbc->list, &percpu_counters);
86         mutex_unlock(&percpu_counters_lock);
87 #endif
88         return 0;
89 }
90 EXPORT_SYMBOL(__percpu_counter_init);
91
92 void percpu_counter_destroy(struct percpu_counter *fbc)
93 {
94         if (!fbc->counters)
95                 return;
96
97         free_percpu(fbc->counters);
98         fbc->counters = NULL;
99 #ifdef CONFIG_HOTPLUG_CPU
100         mutex_lock(&percpu_counters_lock);
101         list_del(&fbc->list);
102         mutex_unlock(&percpu_counters_lock);
103 #endif
104 }
105 EXPORT_SYMBOL(percpu_counter_destroy);
106
107 #ifdef CONFIG_HOTPLUG_CPU
108 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
109                                         unsigned long action, void *hcpu)
110 {
111         unsigned int cpu;
112         struct percpu_counter *fbc;
113
114         if (action != CPU_DEAD)
115                 return NOTIFY_OK;
116
117         cpu = (unsigned long)hcpu;
118         mutex_lock(&percpu_counters_lock);
119         list_for_each_entry(fbc, &percpu_counters, list) {
120                 s32 *pcount;
121                 unsigned long flags;
122
123                 spin_lock_irqsave(&fbc->lock, flags);
124                 pcount = per_cpu_ptr(fbc->counters, cpu);
125                 fbc->count += *pcount;
126                 *pcount = 0;
127                 spin_unlock_irqrestore(&fbc->lock, flags);
128         }
129         mutex_unlock(&percpu_counters_lock);
130         return NOTIFY_OK;
131 }
132
133 static int __init percpu_counter_startup(void)
134 {
135         hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
136         return 0;
137 }
138 module_init(percpu_counter_startup);
139 #endif