idle: Remove GENERIC_IDLE_LOOP config switch
[linux-3.10.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 #include <linux/debugobjects.h>
12
13 #ifdef CONFIG_HOTPLUG_CPU
14 static LIST_HEAD(percpu_counters);
15 static DEFINE_SPINLOCK(percpu_counters_lock);
16 #endif
17
18 #ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
19
20 static struct debug_obj_descr percpu_counter_debug_descr;
21
22 static 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
36 static struct debug_obj_descr percpu_counter_debug_descr = {
37         .name           = "percpu_counter",
38         .fixup_free     = percpu_counter_fixup_free,
39 };
40
41 static 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
47 static 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 */
54 static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
55 { }
56 static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
57 { }
58 #endif  /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
59
60 void 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 }
72 EXPORT_SYMBOL(percpu_counter_set);
73
74 void __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 }
90 EXPORT_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  */
96 s64 __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 }
110 EXPORT_SYMBOL(__percpu_counter_sum);
111
112 int __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         spin_lock(&percpu_counters_lock);
127         list_add(&fbc->list, &percpu_counters);
128         spin_unlock(&percpu_counters_lock);
129 #endif
130         return 0;
131 }
132 EXPORT_SYMBOL(__percpu_counter_init);
133
134 void 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         spin_lock(&percpu_counters_lock);
143         list_del(&fbc->list);
144         spin_unlock(&percpu_counters_lock);
145 #endif
146         free_percpu(fbc->counters);
147         fbc->counters = NULL;
148 }
149 EXPORT_SYMBOL(percpu_counter_destroy);
150
151 int percpu_counter_batch __read_mostly = 32;
152 EXPORT_SYMBOL(percpu_counter_batch);
153
154 static void compute_batch_value(void)
155 {
156         int nr = num_online_cpus();
157
158         percpu_counter_batch = max(32, nr*2);
159 }
160
161 static 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         spin_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         spin_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  */
193 int 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 }
214 EXPORT_SYMBOL(percpu_counter_compare);
215
216 static int __init percpu_counter_startup(void)
217 {
218         compute_batch_value();
219         hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
220         return 0;
221 }
222 module_init(percpu_counter_startup);