Quelle percpu_counter.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#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/spinlock.h>
#include <linux/smp.h>
#include <linux/list.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>

/* percpu_counter batch for local add or sub */
#define PERCPU_COUNTER_LOCAL_BATCH INT_MAX

#ifdef CONFIG_SMP

struct percpu_counter {
raw_spinlock_t lock;
s64 count;
#ifdef CONFIG_HOTPLUG_CPU
struct list_head list; /* All percpu_counters are on a list */
#endif
s32 __percpu *counters;
};

extern int percpu_counter_batch;

int __percpu_counter_init_many(struct percpu_counter *fbc, s64 amount,
          gfp_t gfp, u32 nr_counters,
          struct lock_class_key *key);

#define percpu_counter_init_many(fbc, value, gfp, nr_counters)  \
({        \
  static struct lock_class_key __key;   \
         \
  __percpu_counter_init_many(fbc, value, gfp, nr_counters,\
        &__key);   \
})

#define percpu_counter_init(fbc, value, gfp)    \
percpu_counter_init_many(fbc, value, gfp, 1)

void percpu_counter_destroy_many(struct percpu_counter *fbc, u32 nr_counters);
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
percpu_counter_destroy_many(fbc, 1);
}

void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
         s32 batch);
s64 __percpu_counter_sum(struct percpu_counter *fbc);
int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
bool __percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit,
      s64 amount, s32 batch);
void percpu_counter_sync(struct percpu_counter *fbc);

static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
{
return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
}

static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
}

static inline bool
percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit, s64 amount)
{
return __percpu_counter_limited_add(fbc, limit, amount,
         percpu_counter_batch);
}

/*
* With percpu_counter_add_local() and percpu_counter_sub_local(), counts
* are accumulated in local per cpu counter and not in fbc->count until
* local count overflows PERCPU_COUNTER_LOCAL_BATCH. This makes counter
* write efficient.
* But percpu_counter_sum(), instead of percpu_counter_read(), needs to be
* used to add up the counts from each CPU to account for all the local
* counts. So percpu_counter_add_local() and percpu_counter_sub_local()
* should be used when a counter is updated frequently and read rarely.
*/
static inline void
percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
{
percpu_counter_add_batch(fbc, amount, PERCPU_COUNTER_LOCAL_BATCH);
}

static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
s64 ret = __percpu_counter_sum(fbc);
return ret < 0 ? 0 : ret;
}

static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
return __percpu_counter_sum(fbc);
}

static inline s64 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 s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
/* Prevent reloads of fbc->count */
s64 ret = READ_ONCE(fbc->count);

if (ret >= 0)
  return ret;
return 0;
}

static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
{
return (fbc->counters != NULL);
}

#else /* !CONFIG_SMP */

struct percpu_counter {
s64 count;
};

static inline int percpu_counter_init_many(struct percpu_counter *fbc,
        s64 amount, gfp_t gfp,
        u32 nr_counters)
{
u32 i;

for (i = 0; i < nr_counters; i++)
  fbc[i].count = amount;

return 0;
}

static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
          gfp_t gfp)
{
return percpu_counter_init_many(fbc, amount, gfp, 1);
}

static inline void percpu_counter_destroy_many(struct percpu_counter *fbc,
            u32 nr_counters)
{
}

static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}

static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
{
fbc->count = amount;
}

static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
{
if (fbc->count > rhs)
  return 1;
else if (fbc->count < rhs)
  return -1;
else
  return 0;
}

static inline int
__percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
{
return percpu_counter_compare(fbc, rhs);
}

static inline void
percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
unsigned long flags;

local_irq_save(flags);
fbc->count += amount;
local_irq_restore(flags);
}

static inline bool
percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit, s64 amount)
{
unsigned long flags;
bool good = false;
s64 count;

if (amount == 0)
  return true;

local_irq_save(flags);
count = fbc->count + amount;
if ((amount > 0 && count <= limit) ||
     (amount < 0 && count >= limit)) {
  fbc->count = count;
  good = true;
}
local_irq_restore(flags);
return good;
}

/* non-SMP percpu_counter_add_local is the same with percpu_counter_add */
static inline void
percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
{
percpu_counter_add(fbc, amount);
}

static inline void
percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
{
percpu_counter_add(fbc, amount);
}

static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
return fbc->count;
}

/*
* percpu_counter is intended to track positive numbers. In the UP case the
* number should never be negative.
*/
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
return fbc->count;
}

static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
return percpu_counter_read_positive(fbc);
}

static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
return percpu_counter_read(fbc);
}

static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
{
return true;
}

static inline void percpu_counter_sync(struct percpu_counter *fbc)
{
}
#endif /* CONFIG_SMP */

static inline void percpu_counter_inc(struct percpu_counter *fbc)
{
percpu_counter_add(fbc, 1);
}

static inline void percpu_counter_dec(struct percpu_counter *fbc)
{
percpu_counter_add(fbc, -1);
}

static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
{
percpu_counter_add(fbc, -amount);
}

static inline void
percpu_counter_sub_local(struct percpu_counter *fbc, s64 amount)
{
percpu_counter_add_local(fbc, -amount);
}

#endif /* _LINUX_PERCPU_COUNTER_H */

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