Merge of r4654, r4672, r4684, r4685, r4692: resolver changes. *) Resolver: fixed format specification. Patch by Yichun Zhang (agentzh). *) Support for IPv6 literals and an optional port in resolver. *) Fixed crash in ngx_resolver_cleanup_tree(). If sending a DNS request fails with an error (e.g., when mistakenly trying to send it to a local IP broadcast), such a request is not deleted if there are clients waiting on it. However, it was still erroneously removed from the queue. Later ngx_resolver_cleanup_tree() attempted to remove it from the queue again that resulted in a NULL pointer dereference. *) When "resolver" is configured with a domain name, only the first resolved address was used. Now all addresses will be used. *) Fixed segfault with poll and resolver used. Poll event method needs ngx_cycle->files to work, and use of ngx_exit_cycle without files set caused null pointer dereference in resolver's cleanup on udp socket close.

/*
 * 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

}