view src/core/ngx_spinlock.c @ 7938:dc955d274130

Mail: connections with wrong ALPN protocols are now rejected. This is a recommended behavior by RFC 7301 and is useful for mitigation of protocol confusion attacks [1]. For POP3 and IMAP protocols IANA-assigned ALPN IDs are used [2]. For the SMTP protocol "smtp" is used. [1] https://alpaca-attack.com/ [2] https://www.iana.org/assignments/tls-extensiontype-values/
author Vladimir Homutov <vl@nginx.com>
date Wed, 20 Oct 2021 09:45:34 +0300
parents f737e406aa68
children
line wrap: on
line source


/*
 * 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

}