slub: Deal with config variable dependencies
[linux-2.6.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         }
66         spin_unlock(&fbc->lock);
67         return ret;
68 }
69 EXPORT_SYMBOL(__percpu_counter_sum);
70
71 static struct lock_class_key percpu_counter_irqsafe;
72
73 int 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 }
87 EXPORT_SYMBOL(percpu_counter_init);
88
89 int 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
99 void percpu_counter_destroy(struct percpu_counter *fbc)
100 {
101         if (!fbc->counters)
102                 return;
103
104         free_percpu(fbc->counters);
105 #ifdef CONFIG_HOTPLUG_CPU
106         mutex_lock(&percpu_counters_lock);
107         list_del(&fbc->list);
108         mutex_unlock(&percpu_counters_lock);
109 #endif
110 }
111 EXPORT_SYMBOL(percpu_counter_destroy);
112
113 #ifdef CONFIG_HOTPLUG_CPU
114 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
115                                         unsigned long action, void *hcpu)
116 {
117         unsigned int cpu;
118         struct percpu_counter *fbc;
119
120         if (action != CPU_DEAD)
121                 return NOTIFY_OK;
122
123         cpu = (unsigned long)hcpu;
124         mutex_lock(&percpu_counters_lock);
125         list_for_each_entry(fbc, &percpu_counters, list) {
126                 s32 *pcount;
127                 unsigned long flags;
128
129                 spin_lock_irqsave(&fbc->lock, flags);
130                 pcount = per_cpu_ptr(fbc->counters, cpu);
131                 fbc->count += *pcount;
132                 *pcount = 0;
133                 spin_unlock_irqrestore(&fbc->lock, flags);
134         }
135         mutex_unlock(&percpu_counters_lock);
136         return NOTIFY_OK;
137 }
138
139 static int __init percpu_counter_startup(void)
140 {
141         hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
142         return 0;
143 }
144 module_init(percpu_counter_startup);
145 #endif