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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/atomic.h>
#include <linux/gfp.h>
#include <linux/jiffies.h>
#include <linux/lazy-percpu-counter.h>
#include <linux/percpu.h>
static inline s64 lazy_percpu_counter_atomic_val(s64 v)
{
/* Ensure output is sign extended properly: */
return (v << COUNTER_MOD_BITS) >>
(COUNTER_MOD_BITS + COUNTER_IS_PCPU_BIT);
}
static void lazy_percpu_counter_switch_to_pcpu(struct lazy_percpu_counter *c)
{
u64 __percpu *pcpu_v = alloc_percpu_gfp(u64, GFP_ATOMIC|__GFP_NOWARN);
u64 old, new, v;
if (!pcpu_v)
return;
preempt_disable();
v = atomic64_read(&c->v);
do {
if (lazy_percpu_counter_is_pcpu(v)) {
free_percpu(pcpu_v);
return;
}
old = v;
new = (unsigned long)pcpu_v | 1;
*this_cpu_ptr(pcpu_v) = lazy_percpu_counter_atomic_val(v);
} while ((v = atomic64_cmpxchg(&c->v, old, new)) != old);
preempt_enable();
}
/**
* lazy_percpu_counter_exit: Free resources associated with a
* lazy_percpu_counter
*
* @c: counter to exit
*/
void lazy_percpu_counter_exit(struct lazy_percpu_counter *c)
{
free_percpu(lazy_percpu_counter_is_pcpu(atomic64_read(&c->v)));
}
EXPORT_SYMBOL_GPL(lazy_percpu_counter_exit);
/**
* lazy_percpu_counter_read: Read current value of a lazy_percpu_counter
*
* @c: counter to read
*/
s64 lazy_percpu_counter_read(struct lazy_percpu_counter *c)
{
s64 v = atomic64_read(&c->v);
u64 __percpu *pcpu_v = lazy_percpu_counter_is_pcpu(v);
if (pcpu_v) {
int cpu;
v = 0;
for_each_possible_cpu(cpu)
v += *per_cpu_ptr(pcpu_v, cpu);
} else {
v = lazy_percpu_counter_atomic_val(v);
}
return v;
}
EXPORT_SYMBOL_GPL(lazy_percpu_counter_read);
void lazy_percpu_counter_add_slowpath(struct lazy_percpu_counter *c, s64 i)
{
u64 atomic_i;
u64 old, v = atomic64_read(&c->v);
u64 __percpu *pcpu_v;
atomic_i = i << COUNTER_IS_PCPU_BIT;
atomic_i &= ~COUNTER_MOD_MASK;
atomic_i |= 1ULL << COUNTER_MOD_BITS_START;
do {
pcpu_v = lazy_percpu_counter_is_pcpu(v);
if (pcpu_v) {
this_cpu_add(*pcpu_v, i);
return;
}
old = v;
} while ((v = atomic64_cmpxchg(&c->v, old, old + atomic_i)) != old);
if (unlikely(!(v & COUNTER_MOD_MASK))) {
unsigned long now = jiffies;
if (c->last_wrap &&
unlikely(time_after(c->last_wrap + HZ, now)))
lazy_percpu_counter_switch_to_pcpu(c);
else
c->last_wrap = now;
}
}
EXPORT_SYMBOL(lazy_percpu_counter_add_slowpath);
void lazy_percpu_counter_add_slowpath_noupgrade(struct lazy_percpu_counter *c, s64 i)
{
u64 atomic_i;
u64 old, v = atomic64_read(&c->v);
u64 __percpu *pcpu_v;
atomic_i = i << COUNTER_IS_PCPU_BIT;
atomic_i &= ~COUNTER_MOD_MASK;
do {
pcpu_v = lazy_percpu_counter_is_pcpu(v);
if (pcpu_v) {
this_cpu_add(*pcpu_v, i);
return;
}
old = v;
} while ((v = atomic64_cmpxchg(&c->v, old, old + atomic_i)) != old);
}
EXPORT_SYMBOL(lazy_percpu_counter_add_slowpath_noupgrade);
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