114 lines
2.2 KiB
C
114 lines
2.2 KiB
C
#ifndef _LINUX_PERCPU_COUNTER_H
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#define _LINUX_PERCPU_COUNTER_H
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/*
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* A simple "approximate counter" for use in ext2 and ext3 superblocks.
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*
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* WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
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*/
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#include <linux/config.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#ifdef CONFIG_SMP
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struct percpu_counter {
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spinlock_t lock;
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long count;
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long *counters;
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};
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#if NR_CPUS >= 16
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#define FBC_BATCH (NR_CPUS*2)
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#else
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#define FBC_BATCH (NR_CPUS*4)
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#endif
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static inline void percpu_counter_init(struct percpu_counter *fbc)
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{
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spin_lock_init(&fbc->lock);
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fbc->count = 0;
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fbc->counters = alloc_percpu(long);
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}
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static inline void percpu_counter_destroy(struct percpu_counter *fbc)
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{
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free_percpu(fbc->counters);
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}
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void percpu_counter_mod(struct percpu_counter *fbc, long amount);
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long percpu_counter_sum(struct percpu_counter *fbc);
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static inline long percpu_counter_read(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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/*
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* It is possible for the percpu_counter_read() to return a small negative
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* number for some counter which should never be negative.
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*/
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static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
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{
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long ret = fbc->count;
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barrier(); /* Prevent reloads of fbc->count */
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if (ret > 0)
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return ret;
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return 1;
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}
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#else
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struct percpu_counter {
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long count;
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};
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static inline void percpu_counter_init(struct percpu_counter *fbc)
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{
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fbc->count = 0;
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}
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static inline void percpu_counter_destroy(struct percpu_counter *fbc)
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{
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}
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static inline void
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percpu_counter_mod(struct percpu_counter *fbc, long amount)
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{
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preempt_disable();
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fbc->count += amount;
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preempt_enable();
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}
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static inline long percpu_counter_read(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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static inline long percpu_counter_sum(struct percpu_counter *fbc)
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{
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return percpu_counter_read_positive(fbc);
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}
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#endif /* CONFIG_SMP */
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static inline void percpu_counter_inc(struct percpu_counter *fbc)
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{
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percpu_counter_mod(fbc, 1);
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}
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static inline void percpu_counter_dec(struct percpu_counter *fbc)
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{
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percpu_counter_mod(fbc, -1);
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}
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#endif /* _LINUX_PERCPU_COUNTER_H */
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