Root/lib/percpu_counter.c

Source at commit b386be689295730688885552666ea40b2e639b14 created 8 years 11 months ago.
By Maarten ter Huurne, Revert "MIPS: JZ4740: reset: Initialize hibernate wakeup counters."
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#include <linux/debugobjects.h>
12
13#ifdef CONFIG_HOTPLUG_CPU
14static LIST_HEAD(percpu_counters);
15static DEFINE_MUTEX(percpu_counters_lock);
16#endif
17
18#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
19
20static struct debug_obj_descr percpu_counter_debug_descr;
21
22static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state)
23{
24    struct percpu_counter *fbc = addr;
25
26    switch (state) {
27    case ODEBUG_STATE_ACTIVE:
28        percpu_counter_destroy(fbc);
29        debug_object_free(fbc, &percpu_counter_debug_descr);
30        return 1;
31    default:
32        return 0;
33    }
34}
35
36static struct debug_obj_descr percpu_counter_debug_descr = {
37    .name = "percpu_counter",
38    .fixup_free = percpu_counter_fixup_free,
39};
40
41static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
42{
43    debug_object_init(fbc, &percpu_counter_debug_descr);
44    debug_object_activate(fbc, &percpu_counter_debug_descr);
45}
46
47static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
48{
49    debug_object_deactivate(fbc, &percpu_counter_debug_descr);
50    debug_object_free(fbc, &percpu_counter_debug_descr);
51}
52
53#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
54static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
55{ }
56static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
57{ }
58#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
59
60void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
61{
62    int cpu;
63
64    raw_spin_lock(&fbc->lock);
65    for_each_possible_cpu(cpu) {
66        s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
67        *pcount = 0;
68    }
69    fbc->count = amount;
70    raw_spin_unlock(&fbc->lock);
71}
72EXPORT_SYMBOL(percpu_counter_set);
73
74void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
75{
76    s64 count;
77
78    preempt_disable();
79    count = __this_cpu_read(*fbc->counters) + amount;
80    if (count >= batch || count <= -batch) {
81        raw_spin_lock(&fbc->lock);
82        fbc->count += count;
83        __this_cpu_write(*fbc->counters, 0);
84        raw_spin_unlock(&fbc->lock);
85    } else {
86        __this_cpu_write(*fbc->counters, count);
87    }
88    preempt_enable();
89}
90EXPORT_SYMBOL(__percpu_counter_add);
91
92/*
93 * Add up all the per-cpu counts, return the result. This is a more accurate
94 * but much slower version of percpu_counter_read_positive()
95 */
96s64 __percpu_counter_sum(struct percpu_counter *fbc)
97{
98    s64 ret;
99    int cpu;
100
101    raw_spin_lock(&fbc->lock);
102    ret = fbc->count;
103    for_each_online_cpu(cpu) {
104        s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
105        ret += *pcount;
106    }
107    raw_spin_unlock(&fbc->lock);
108    return ret;
109}
110EXPORT_SYMBOL(__percpu_counter_sum);
111
112int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
113              struct lock_class_key *key)
114{
115    raw_spin_lock_init(&fbc->lock);
116    lockdep_set_class(&fbc->lock, key);
117    fbc->count = amount;
118    fbc->counters = alloc_percpu(s32);
119    if (!fbc->counters)
120        return -ENOMEM;
121
122    debug_percpu_counter_activate(fbc);
123
124#ifdef CONFIG_HOTPLUG_CPU
125    INIT_LIST_HEAD(&fbc->list);
126    mutex_lock(&percpu_counters_lock);
127    list_add(&fbc->list, &percpu_counters);
128    mutex_unlock(&percpu_counters_lock);
129#endif
130    return 0;
131}
132EXPORT_SYMBOL(__percpu_counter_init);
133
134void percpu_counter_destroy(struct percpu_counter *fbc)
135{
136    if (!fbc->counters)
137        return;
138
139    debug_percpu_counter_deactivate(fbc);
140
141#ifdef CONFIG_HOTPLUG_CPU
142    mutex_lock(&percpu_counters_lock);
143    list_del(&fbc->list);
144    mutex_unlock(&percpu_counters_lock);
145#endif
146    free_percpu(fbc->counters);
147    fbc->counters = NULL;
148}
149EXPORT_SYMBOL(percpu_counter_destroy);
150
151int percpu_counter_batch __read_mostly = 32;
152EXPORT_SYMBOL(percpu_counter_batch);
153
154static void compute_batch_value(void)
155{
156    int nr = num_online_cpus();
157
158    percpu_counter_batch = max(32, nr*2);
159}
160
161static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
162                    unsigned long action, void *hcpu)
163{
164#ifdef CONFIG_HOTPLUG_CPU
165    unsigned int cpu;
166    struct percpu_counter *fbc;
167
168    compute_batch_value();
169    if (action != CPU_DEAD)
170        return NOTIFY_OK;
171
172    cpu = (unsigned long)hcpu;
173    mutex_lock(&percpu_counters_lock);
174    list_for_each_entry(fbc, &percpu_counters, list) {
175        s32 *pcount;
176        unsigned long flags;
177
178        raw_spin_lock_irqsave(&fbc->lock, flags);
179        pcount = per_cpu_ptr(fbc->counters, cpu);
180        fbc->count += *pcount;
181        *pcount = 0;
182        raw_spin_unlock_irqrestore(&fbc->lock, flags);
183    }
184    mutex_unlock(&percpu_counters_lock);
185#endif
186    return NOTIFY_OK;
187}
188
189/*
190 * Compare counter against given value.
191 * Return 1 if greater, 0 if equal and -1 if less
192 */
193int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
194{
195    s64 count;
196
197    count = percpu_counter_read(fbc);
198    /* Check to see if rough count will be sufficient for comparison */
199    if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) {
200        if (count > rhs)
201            return 1;
202        else
203            return -1;
204    }
205    /* Need to use precise count */
206    count = percpu_counter_sum(fbc);
207    if (count > rhs)
208        return 1;
209    else if (count < rhs)
210        return -1;
211    else
212        return 0;
213}
214EXPORT_SYMBOL(percpu_counter_compare);
215
216static int __init percpu_counter_startup(void)
217{
218    compute_batch_value();
219    hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
220    return 0;
221}
222module_init(percpu_counter_startup);
223

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