Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux...
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / lib / percpu_counter.c
blobb255b939bc1b85bd4fc385df4e1322e9472b2b26
1 /*
2 * Fast batching percpu counters.
3 */
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>
12 #ifdef CONFIG_HOTPLUG_CPU
13 static LIST_HEAD(percpu_counters);
14 static DEFINE_MUTEX(percpu_counters_lock);
15 #endif
17 void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
19 int cpu;
21 spin_lock(&fbc->lock);
22 for_each_possible_cpu(cpu) {
23 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
24 *pcount = 0;
26 fbc->count = amount;
27 spin_unlock(&fbc->lock);
29 EXPORT_SYMBOL(percpu_counter_set);
31 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
33 s64 count;
34 s32 *pcount;
35 int cpu = get_cpu();
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;
47 put_cpu();
49 EXPORT_SYMBOL(__percpu_counter_add);
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()
55 s64 __percpu_counter_sum(struct percpu_counter *fbc)
57 s64 ret;
58 int cpu;
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;
66 spin_unlock(&fbc->lock);
67 return ret;
69 EXPORT_SYMBOL(__percpu_counter_sum);
71 static struct lock_class_key percpu_counter_irqsafe;
73 int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
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;
87 EXPORT_SYMBOL(percpu_counter_init);
89 int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
91 int err;
93 err = percpu_counter_init(fbc, amount);
94 if (!err)
95 lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
96 return err;
99 void percpu_counter_destroy(struct percpu_counter *fbc)
101 if (!fbc->counters)
102 return;
104 #ifdef CONFIG_HOTPLUG_CPU
105 mutex_lock(&percpu_counters_lock);
106 list_del(&fbc->list);
107 mutex_unlock(&percpu_counters_lock);
108 #endif
109 free_percpu(fbc->counters);
110 fbc->counters = NULL;
112 EXPORT_SYMBOL(percpu_counter_destroy);
114 #ifdef CONFIG_HOTPLUG_CPU
115 static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
116 unsigned long action, void *hcpu)
118 unsigned int cpu;
119 struct percpu_counter *fbc;
121 if (action != CPU_DEAD)
122 return NOTIFY_OK;
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;
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);
136 mutex_unlock(&percpu_counters_lock);
137 return NOTIFY_OK;
140 static int __init percpu_counter_startup(void)
142 hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
143 return 0;
145 module_init(percpu_counter_startup);
146 #endif