view src/core/ngx_spinlock.c @ 4729:4ff2131dbce5 stable-1.2

Merge of r4691: changed default alignment to 16. This fixes alignment problems observerd on ARMs, and likely also needed for MIPSes. Unless we know alignment is not required just assume we need 16, which appears to be safe default for all architectures. See here for details: http://mailman.nginx.org/pipermail/nginx/2012-June/034139.html
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 02 Jul 2012 17:08:26 +0000
parents d620f497c50f
children 457ec43dd8d5
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#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

}