release/src/router/nginx/src/core/ngx_spinlock.c

   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
  12 void
  13 ngx_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 }