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