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