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src/core/ngx_spinlock.c - nginx-1.7.10

Functions defined

Source code


  2. /*
  3. * Copyright (C) Igor Sysoev
  4. * Copyright (C) Nginx, Inc.
  5. */


  8. #include <ngx_config.h>
  9. #include <ngx_core.h>


  12. void
  13. ‌ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin)
  14. {

  16. #if (NGX_HAVE_ATOMIC_OPS)

  18.     ngx_uint_t  i, n;

  20.     for ( ;; ) {

  22.         if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
  23.             return;
  24.         }

  26.         if (ngx_ncpu > 1) {

  28.             for (n = 1; n < spin; n <<= 1) {

  30.                 for (i = 0; i < n; i++) {
  31.                     ngx_cpu_pause();
  32.                 }

  34.                 if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
  35.                     return;
  36.                 }
  37.             }
  38.         }

  40.         ngx_sched_yield();
  41.     }

  43. #else

  45. #if (NGX_THREADS)

  47. #error ngx_spinlock() or ngx_atomic_cmp_set() are not defined !

  49. #endif

  51. #endif

  53. }

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