1
2/*
3 * Copyright (C) Igor Sysoev
4 * Copyright (C) Nginx, Inc.
5 */
6
7
8#include <ngx_config.h>
9#include <ngx_core.h>
10
11
12void
13ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin)
14{
15
16#if (NGX_HAVE_ATOMIC_OPS)
17
18    ngx_uint_t  i, n;
19
20    for ( ;; ) {
21
22        if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
23            return;
24        }
25
26        if (ngx_ncpu > 1) {
27
28            for (n = 1; n < spin; n <<= 1) {
29
30                for (i = 0; i < n; i++) {
31                    ngx_cpu_pause();
32                }
33
34                if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
35                    return;
36                }
37            }
38        }
39
40        ngx_sched_yield();
41    }
42
43#else
44
45#if (NGX_THREADS)
46
47#error ngx_spinlock() or ngx_atomic_cmp_set() are not defined !
48
49#endif
50
51#endif
52
53}
54