percpu counter: clean up percpu_counter_sum_and_set()
[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                 *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 static struct lock_class_key percpu_counter_irqsafe;
75
76 int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
77 {
78         spin_lock_init(&fbc->lock);
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 int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
93 {
94         int err;
95
96         err = percpu_counter_init(fbc, amount);
97         if (!err)
98                 lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
99         return err;
100 }
101
102 void percpu_counter_destroy(struct percpu_counter *fbc)
103 {
104         if (!fbc->counters)
105                 return;
106
107         free_percpu(fbc->counters);
108         fbc->counters = NULL;
109 #ifdef CONFIG_HOTPLUG_CPU
110         mutex_lock(&percpu_counters_lock);
111         list_del(&fbc->list);
112         mutex_unlock(&percpu_counters_lock);
113 #endif
114 }
115 EXPORT_SYMBOL(percpu_counter_destroy);
116
117 #ifdef CONFIG_HOTPLUG_CPU
118 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
119                                         unsigned long action, void *hcpu)
120 {
121         unsigned int cpu;
122         struct percpu_counter *fbc;
123
124         if (action != CPU_DEAD)
125                 return NOTIFY_OK;
126
127         cpu = (unsigned long)hcpu;
128         mutex_lock(&percpu_counters_lock);
129         list_for_each_entry(fbc, &percpu_counters, list) {
130                 s32 *pcount;
131                 unsigned long flags;
132
133                 spin_lock_irqsave(&fbc->lock, flags);
134                 pcount = per_cpu_ptr(fbc->counters, cpu);
135                 fbc->count += *pcount;
136                 *pcount = 0;
137                 spin_unlock_irqrestore(&fbc->lock, flags);
138         }
139         mutex_unlock(&percpu_counters_lock);
140         return NOTIFY_OK;
141 }
142
143 static int __init percpu_counter_startup(void)
144 {
145         hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
146         return 0;
147 }
148 module_init(percpu_counter_startup);
149 #endif