nginx 0.8.16 *) Feature: the "image_filter_transparency" directive. *) Bugfix: "addition_types" directive was incorrectly named "addtion_types". *) Bugfix: resolver cache poisoning. Thanks to Matthew Dempsky. *) Bugfix: memory leak in resolver. Thanks to Matthew Dempsky. *) Bugfix: invalid request line in $request variable was written in access_log only if error_log was set to "info" or "debug" level. *) Bugfix: in PNG alpha-channel support in the ngx_http_image_filter_module. *) Bugfix: nginx always added "Vary: Accept-Encoding" response header line, if both "gzip_static" and "gzip_vary" were on. *) Bugfix: in UTF-8 encoding support by "try_files" directive in nginx/Windows. *) Bugfix: in "post_action" directive usage; the bug had appeared in 0.8.11. Thanks to Igor Artemiev.

/*
 * Copyright (C) Igor Sysoev
 */


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


void
ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin)
{

#if (NGX_HAVE_ATOMIC_OPS)

    ngx_uint_t  i, n;

    for ( ;; ) {

        if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
            return;
        }

        if (ngx_ncpu > 1) {

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

                for (i = 0; i < n; i++) {
                    ngx_cpu_pause();
                }

                if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) {
                    return;
                }
            }
        }

        ngx_sched_yield();
    }

#else

#if (NGX_THREADS)

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

#endif

#endif

}