percpu_counter: new function 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, int set)
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                 if (set)
66                         *pcount = 0;
67         }
68         if (set)
69                 fbc->count = ret;
70
71         spin_unlock(&fbc->lock);
72         return ret;
73 }
74 EXPORT_SYMBOL(__percpu_counter_sum);
75
76 static struct lock_class_key percpu_counter_irqsafe;
77
78 int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
79 {
80         spin_lock_init(&fbc->lock);
81         fbc->count = amount;
82         fbc->counters = alloc_percpu(s32);
83         if (!fbc->counters)
84                 return -ENOMEM;
85 #ifdef CONFIG_HOTPLUG_CPU
86         mutex_lock(&percpu_counters_lock);
87         list_add(&fbc->list, &percpu_counters);
88         mutex_unlock(&percpu_counters_lock);
89 #endif
90         return 0;
91 }
92 EXPORT_SYMBOL(percpu_counter_init);
93
94 int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
95 {
96         int err;
97
98         err = percpu_counter_init(fbc, amount);
99         if (!err)
100                 lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
101         return err;
102 }
103
104 void percpu_counter_destroy(struct percpu_counter *fbc)
105 {
106         if (!fbc->counters)
107                 return;
108
109         free_percpu(fbc->counters);
110         fbc->counters = NULL;
111 #ifdef CONFIG_HOTPLUG_CPU
112         mutex_lock(&percpu_counters_lock);
113         list_del(&fbc->list);
114         mutex_unlock(&percpu_counters_lock);
115 #endif
116 }
117 EXPORT_SYMBOL(percpu_counter_destroy);
118
119 #ifdef CONFIG_HOTPLUG_CPU
120 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
121                                         unsigned long action, void *hcpu)
122 {
123         unsigned int cpu;
124         struct percpu_counter *fbc;
125
126         if (action != CPU_DEAD)
127                 return NOTIFY_OK;
128
129         cpu = (unsigned long)hcpu;
130         mutex_lock(&percpu_counters_lock);
131         list_for_each_entry(fbc, &percpu_counters, list) {
132                 s32 *pcount;
133                 unsigned long flags;
134
135                 spin_lock_irqsave(&fbc->lock, flags);
136                 pcount = per_cpu_ptr(fbc->counters, cpu);
137                 fbc->count += *pcount;
138                 *pcount = 0;
139                 spin_unlock_irqrestore(&fbc->lock, flags);
140         }
141         mutex_unlock(&percpu_counters_lock);
142         return NOTIFY_OK;
143 }
144
145 static int __init percpu_counter_startup(void)
146 {
147         hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
148         return 0;
149 }
150 module_init(percpu_counter_startup);
151 #endif