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/*
* Copyright (C) Ruslan Ermilov
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
#if (NGX_HAVE_ATOMIC_OPS)
#define NGX_RWLOCK_SPIN 2048
#define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1)
void
ngx_rwlock_wlock(ngx_atomic_t *lock)
{
ngx_uint_t i, n;
for ( ;; ) {
if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) {
return;
}
if (ngx_ncpu > 1) {
for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {
for (i = 0; i < n; i++) {
ngx_cpu_pause();
}
if (*lock == 0
&& ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK))
{
return;
}
}
}
ngx_sched_yield();
}
}
void
ngx_rwlock_rlock(ngx_atomic_t *lock)
{
ngx_uint_t i, n;
ngx_atomic_uint_t readers;
for ( ;; ) {
readers = *lock;
if (readers != NGX_RWLOCK_WLOCK
&& ngx_atomic_cmp_set(lock, readers, readers + 1))
{
return;
}
if (ngx_ncpu > 1) {
for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {
for (i = 0; i < n; i++) {
ngx_cpu_pause();
}
readers = *lock;
if (readers != NGX_RWLOCK_WLOCK
&& ngx_atomic_cmp_set(lock, readers, readers + 1))
{
return;
}
}
}
ngx_sched_yield();
}
}
void
ngx_rwlock_unlock(ngx_atomic_t *lock)
{
ngx_atomic_uint_t readers;
readers = *lock;
if (readers == NGX_RWLOCK_WLOCK) {
*lock = 0;
return;
}
for ( ;; ) {
if (ngx_atomic_cmp_set(lock, readers, readers - 1)) {
return;
}
readers = *lock;
}
}
#else
#if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE)
#error ngx_atomic_cmp_set() is not defined!
#endif
#endif
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