new file mode 100644
--- /dev/null
+++ b/src/os/unix/ngx_freebsd_rfork_thread.c
@@ -0,0 +1,738 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+
+/*
+ * The threads implementation uses the rfork(RFPROC|RFTHREAD|RFMEM) syscall
+ * to create threads.  All threads use the stacks of the same size mmap()ed
+ * below the main stack.  Thus the current thread id is determinated via
+ * the stack pointer value.
+ *
+ * The mutex implementation uses the ngx_atomic_cmp_set() operation
+ * to acquire a mutex and the SysV semaphore to wait on a mutex and to wake up
+ * the waiting threads.  The light mutex does not use semaphore, so after
+ * spinning in the lock the thread calls sched_yield().  However the light
+ * mutecies are intended to be used with the "trylock" operation only.
+ * The SysV semop() is a cheap syscall, particularly if it has little sembuf's
+ * and does not use SEM_UNDO.
+ *
+ * The condition variable implementation uses signal #64.  The signal handler
+ * is SIG_IGN so the kill() is a cheap syscall.  The thread waits a signal
+ * in kevent().  The use of the EVFILT_SIGNAL is safe since FreeBSD 4.7.
+ *
+ * This threads implementation currently works on i386 (486+) and amd64
+ * platforms only.
+ */
+
+
+char                 *ngx_freebsd_kern_usrstack;
+size_t                ngx_thread_stack_size;
+
+
+static size_t         rz_size;
+static size_t         usable_stack_size;
+static char          *last_stack;
+
+static ngx_uint_t     nthreads;
+static ngx_uint_t     max_threads;
+
+static ngx_uint_t     nkeys;
+static ngx_tid_t     *tids;      /* the threads tids array */
+void                **ngx_tls;   /* the threads tls's array */
+
+/* the thread-safe libc errno */
+
+static int   errno0;   /* the main thread's errno */
+static int  *errnos;   /* the threads errno's array */
+
+int *__error()
+{
+    int  tid;
+
+    tid = ngx_gettid();
+
+    return tid ? &errnos[tid - 1] : &errno0;
+}
+
+
+/*
+ * __isthreaded enables the spinlocks in some libc functions, i.e. in malloc()
+ * and some other places.  Nevertheless we protect our malloc()/free() calls
+ * by own mutex that is more efficient than the spinlock.
+ *
+ * _spinlock() is a weak referenced stub in src/lib/libc/gen/_spinlock_stub.c
+ * that does nothing.
+ */
+
+extern int  __isthreaded;
+
+void _spinlock(ngx_atomic_t *lock)
+{
+    ngx_int_t  tries;
+
+    tries = 0;
+
+    for ( ;; ) {
+
+        if (*lock) {
+            if (ngx_ncpu > 1 && tries++ < 1000) {
+                continue;
+            }
+
+            sched_yield();
+            tries = 0;
+
+        } else {
+            if (ngx_atomic_cmp_set(lock, 0, 1)) {
+                return;
+            }
+        }
+    }
+}
+
+
+/*
+ * Before FreeBSD 5.1 _spinunlock() is a simple #define in
+ * src/lib/libc/include/spinlock.h that zeroes lock.
+ *
+ * Since FreeBSD 5.1 _spinunlock() is a weak referenced stub in
+ * src/lib/libc/gen/_spinlock_stub.c that does nothing.
+ */
+
+#ifndef _spinunlock
+
+void _spinunlock(ngx_atomic_t *lock)
+{
+    *lock = 0;
+}
+
+#endif
+
+
+int ngx_create_thread(ngx_tid_t *tid, void* (*func)(void *arg), void *arg,
+                      ngx_log_t *log)
+{
+    int    id, err;
+    char  *stack, *stack_top;
+
+    if (nthreads >= max_threads) {
+        ngx_log_error(NGX_LOG_CRIT, log, 0,
+                      "no more than %d threads can be created", max_threads);
+        return NGX_ERROR;
+    }
+
+    last_stack -= ngx_thread_stack_size;
+
+    stack = mmap(last_stack, usable_stack_size, PROT_READ|PROT_WRITE,
+                 MAP_STACK, -1, 0);
+
+    if (stack == MAP_FAILED) {
+        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
+                      "mmap(" PTR_FMT ":" SIZE_T_FMT
+                      ", MAP_STACK) thread stack failed",
+                      last_stack, usable_stack_size);
+        return NGX_ERROR;
+    }
+
+    if (stack != last_stack) {
+        ngx_log_error(NGX_LOG_ALERT, log, 0, "stack address was changed");
+    }
+
+    stack_top = stack + usable_stack_size;
+
+    ngx_log_debug2(NGX_LOG_DEBUG_CORE, log, 0,
+                   "thread stack: " PTR_FMT "-" PTR_FMT, stack, stack_top);
+
+    ngx_set_errno(0);
+
+    id = rfork_thread(RFPROC|RFTHREAD|RFMEM, stack_top,
+                      (ngx_rfork_thread_func_pt) func, arg);
+
+    err = ngx_errno;
+
+    if (id == -1) {
+        ngx_log_error(NGX_LOG_ALERT, log, err, "rfork() failed");
+
+    } else {
+        *tid = id;
+        nthreads = (ngx_freebsd_kern_usrstack - stack_top)
+                                                       / ngx_thread_stack_size;
+        tids[nthreads] = id;
+
+        ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0, "rfork()ed thread: %d", id);
+    }
+
+    return err;
+}
+
+
+ngx_int_t ngx_init_threads(int n, size_t size, ngx_cycle_t *cycle)
+{
+    char              *red_zone, *zone;
+    size_t             len;
+    ngx_int_t          i;
+    struct sigaction   sa;
+
+    max_threads = n + 1;
+
+    for (i = 0; i < n; i++) {
+        ngx_memzero(&sa, sizeof(struct sigaction));
+        sa.sa_handler = SIG_IGN;
+        sigemptyset(&sa.sa_mask);
+        if (sigaction(NGX_CV_SIGNAL, &sa, NULL) == -1) {
+            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
+                          "sigaction(%d, SIG_IGN) failed", NGX_CV_SIGNAL);
+            return NGX_ERROR;
+        }
+    }
+
+    len = sizeof(ngx_freebsd_kern_usrstack);
+    if (sysctlbyname("kern.usrstack", &ngx_freebsd_kern_usrstack, &len,
+                                                                NULL, 0) == -1)
+    {
+        ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
+                      "sysctlbyname(kern.usrstack) failed");
+        return NGX_ERROR;
+    }
+
+    /* the main thread stack red zone */
+    rz_size = ngx_pagesize;
+    red_zone = ngx_freebsd_kern_usrstack - (size + rz_size);
+
+    ngx_log_debug2(NGX_LOG_DEBUG_CORE, cycle->log, 0,
+                   "usrstack: " PTR_FMT " red zone: " PTR_FMT,
+                   ngx_freebsd_kern_usrstack, red_zone);
+
+    zone = mmap(red_zone, rz_size, PROT_NONE, MAP_ANON, -1, 0);
+    if (zone == MAP_FAILED) {
+        ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
+                      "mmap(" PTR_FMT ":" SIZE_T_FMT
+                      ", PROT_NONE, MAP_ANON) red zone failed",
+                      red_zone, rz_size);
+        return NGX_ERROR;
+    }
+
+    if (zone != red_zone) {
+        ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
+                      "red zone address was changed");
+    }
+
+    /* create the threads errno's array */
+
+    if (!(errnos = ngx_calloc(n * sizeof(int), cycle->log))) {
+        return NGX_ERROR;
+    }
+
+    /* create the threads tids array */
+
+    if (!(tids = ngx_calloc((n + 1) * sizeof(ngx_tid_t), cycle->log))) {
+        return NGX_ERROR;
+    }
+
+    tids[0] = ngx_pid;
+
+    /* create the threads tls's array */
+
+    ngx_tls = ngx_calloc(NGX_THREAD_KEYS_MAX * (n + 1) * sizeof(void *),
+                         cycle->log);
+    if (ngx_tls == NULL) {
+        return NGX_ERROR;
+    }
+
+    nthreads = 1;
+
+    last_stack = zone + rz_size;
+    usable_stack_size = size;
+    ngx_thread_stack_size = size + rz_size;
+
+    /* allow the spinlock in libc malloc() */
+    __isthreaded = 1;
+
+    ngx_threaded = 1;
+
+    return NGX_OK;
+}
+
+
+ngx_tid_t ngx_thread_self()
+{
+    int        tid;
+    ngx_tid_t  pid;
+
+    tid = ngx_gettid();
+
+    if (tids == NULL) {
+        return ngx_pid;
+    }
+
+    return tids[tid];
+}
+
+
+ngx_int_t ngx_thread_key_create(ngx_tls_key_t *key)
+{
+    if (nkeys >= NGX_THREAD_KEYS_MAX) {
+        return NGX_ENOMEM;
+    }
+
+    *key = nkeys++;
+
+    return 0;
+}
+
+
+ngx_int_t ngx_thread_set_tls(ngx_tls_key_t key, void *value)
+{
+    if (key >= NGX_THREAD_KEYS_MAX) {
+        return NGX_EINVAL;
+    }
+
+    ngx_tls[key * NGX_THREAD_KEYS_MAX + ngx_gettid()] = value;
+    return 0;
+}
+
+
+ngx_mutex_t *ngx_mutex_init(ngx_log_t *log, uint flags)
+{
+    ngx_mutex_t  *m;
+    union semun   op;
+
+    if (!(m = ngx_alloc(sizeof(ngx_mutex_t), log))) {
+        return NULL;
+    }
+
+    m->lock = 0;
+    m->log = log;
+
+    if (flags & NGX_MUTEX_LIGHT) {
+        m->semid = -1;
+        return m;
+    }
+
+    m->semid = semget(IPC_PRIVATE, 1, SEM_R|SEM_A);
+    if (m->semid == -1) {
+        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno, "semget() failed");
+        return NULL;
+    }
+
+    op.val = 0;
+
+    if (semctl(m->semid, 0, SETVAL, op) == -1) {
+        ngx_log_error(NGX_LOG_ALERT, log, ngx_errno, "semctl(SETVAL) failed");
+
+        if (semctl(m->semid, 0, IPC_RMID) == -1) {
+            ngx_log_error(NGX_LOG_ALERT, log, ngx_errno,
+                          "semctl(IPC_RMID) failed");
+        }
+
+        return NULL;
+    }
+
+    return m;
+}
+
+
+void ngx_mutex_destroy(ngx_mutex_t *m)
+{
+    if (semctl(m->semid, 0, IPC_RMID) == -1) {
+        ngx_log_error(NGX_LOG_ALERT, m->log, ngx_errno,
+                      "semctl(IPC_RMID) failed");
+    }
+
+    ngx_free((void *) m);
+}
+
+
+ngx_int_t ngx_mutex_dolock(ngx_mutex_t *m, ngx_int_t try)
+{
+    uint32_t       lock, new, old;
+    ngx_uint_t     tries;
+    struct sembuf  op;
+
+    if (!ngx_threaded) {
+        return NGX_OK;
+    }
+
+#if (NGX_DEBUG)
+    if (try) {
+        ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                       "try lock mutex " PTR_FMT " lock:%X", m, m->lock);
+    } else {
+        ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                       "lock mutex " PTR_FMT " lock:%X", m, m->lock);
+    }
+#endif
+
+    old = m->lock;
+    tries = 0;
+
+    for ( ;; ) {
+        if (old & NGX_MUTEX_LOCK_BUSY) {
+
+            if (try) {
+                return NGX_AGAIN;
+            }
+
+            if (ngx_freebsd_hw_ncpu > 1 && tries++ < 1000) {
+
+                /* the spinlock is used only on the SMP system */
+
+                old = m->lock;
+                continue;
+            }
+
+            if (m->semid == -1) {
+                sched_yield();
+
+                tries = 0;
+                old = m->lock;
+                continue;
+            }
+
+            ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                           "mutex " PTR_FMT " lock:%X", m, m->lock);
+
+            /*
+             * The mutex is locked so we increase a number
+             * of the threads that are waiting on the mutex
+             */
+
+            lock = old + 1;
+
+            if ((lock & ~NGX_MUTEX_LOCK_BUSY) > nthreads) {
+                ngx_log_error(NGX_LOG_ALERT, m->log, ngx_errno,
+                              "%d threads wait for mutex " PTR_FMT
+                              ", while only %d threads are available",
+                              lock & ~NGX_MUTEX_LOCK_BUSY, m, nthreads);
+                return NGX_ERROR;
+            }
+
+            if (ngx_atomic_cmp_set(&m->lock, old, lock)) {
+
+                ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                               "wait mutex " PTR_FMT " lock:%X", m, m->lock);
+
+                /*
+                 * The number of the waiting threads has been increased
+                 * and we would wait on the SysV semaphore.
+                 * A semaphore should wake up us more efficiently than
+                 * a simple sched_yield() or usleep().
+                 */
+
+                op.sem_num = 0;
+                op.sem_op = -1;
+                op.sem_flg = 0;
+
+                if (semop(m->semid, &op, 1) == -1) {
+                    ngx_log_error(NGX_LOG_ALERT, m->log, ngx_errno,
+                                  "semop() failed while waiting "
+                                  "on mutex " PTR_FMT, m);
+                    return NGX_ERROR;
+                }
+
+                ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                               "mutex waked up " PTR_FMT " lock:%X",
+                               m, m->lock);
+
+                tries = 0;
+                old = m->lock;
+                continue;
+            }
+
+            old = m->lock;
+
+        } else {
+            lock = old | NGX_MUTEX_LOCK_BUSY;
+
+            if (ngx_atomic_cmp_set(&m->lock, old, lock)) {
+
+                /* we locked the mutex */
+
+                break;
+            }
+
+            old = m->lock;
+        }
+
+        if (tries++ > 1000) {
+
+            ngx_log_debug1(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                           "mutex " PTR_FMT " is contested", m);
+
+            /* the mutex is probably contested so we are giving up now */
+
+            sched_yield();
+
+            tries = 0;
+            old = m->lock;
+        }
+    }
+
+    ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                   "mutex " PTR_FMT " is locked, lock:%X", m, m->lock);
+
+    return NGX_OK;
+}
+
+
+ngx_int_t ngx_mutex_unlock(ngx_mutex_t *m)
+{
+    uint32_t       lock, new, old;
+    struct sembuf  op;
+
+    if (!ngx_threaded) {
+        return NGX_OK;
+    }
+
+    old = m->lock;
+
+    if (!(old & NGX_MUTEX_LOCK_BUSY)) {
+        ngx_log_error(NGX_LOG_ALERT, m->log, 0,
+                      "trying to unlock the free mutex " PTR_FMT, m);
+        return NGX_ERROR;
+    }
+
+    /* free the mutex */
+
+#if 0
+    ngx_log_debug2(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                   "unlock mutex " PTR_FMT " lock:%X", m, old);
+#endif
+
+    for ( ;; ) {
+        lock = old & ~NGX_MUTEX_LOCK_BUSY;
+
+        if (ngx_atomic_cmp_set(&m->lock, old, lock)) {
+            break;
+        }
+
+        old = m->lock;
+    }
+
+    if (m->semid == -1) {
+        ngx_log_debug1(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                       "mutex " PTR_FMT " is unlocked", m);
+
+        return NGX_OK;
+    }
+
+    /* check whether we need to wake up a waiting thread */
+
+    old = m->lock;
+
+    for ( ;; ) {
+        if (old & NGX_MUTEX_LOCK_BUSY) {
+
+            /* the mutex is just locked by another thread */
+
+            break;
+        }
+
+        if (old == 0) {
+            break;
+        }
+
+        /* there are the waiting threads */
+
+        lock = old - 1;
+
+        if (ngx_atomic_cmp_set(&m->lock, old, lock)) {
+
+            /* wake up the thread that waits on semaphore */
+
+            ngx_log_debug1(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                           "wake up mutex " PTR_FMT "", m);
+
+            op.sem_num = 0;
+            op.sem_op = 1;
+            op.sem_flg = 0;
+
+            if (semop(m->semid, &op, 1) == -1) {
+                ngx_log_error(NGX_LOG_ALERT, m->log, ngx_errno,
+                              "semop() failed while waking up on mutex "
+                              PTR_FMT, m);
+                return NGX_ERROR;
+            }
+
+            break;
+        }
+
+        old = m->lock;
+    }
+
+    ngx_log_debug1(NGX_LOG_DEBUG_MUTEX, m->log, 0,
+                   "mutex " PTR_FMT " is unlocked", m);
+
+    return NGX_OK;
+}
+
+
+ngx_cond_t *ngx_cond_init(ngx_log_t *log)
+{
+    ngx_cond_t  *cv;
+
+    if (!(cv = ngx_alloc(sizeof(ngx_cond_t), log))) {
+        return NULL;
+    }
+
+    cv->signo = NGX_CV_SIGNAL;
+    cv->tid = 0;
+    cv->log = log;
+    cv->kq = -1;
+
+    return cv;
+}
+
+
+void ngx_cond_destroy(ngx_cond_t *cv)
+{
+    if (close(cv->kq) == -1) {
+        ngx_log_error(NGX_LOG_ALERT, cv->log, ngx_errno,
+                      "kqueue close() failed");
+    }
+
+    ngx_free(cv);
+}
+
+
+ngx_int_t ngx_cond_wait(ngx_cond_t *cv, ngx_mutex_t *m)
+{
+    int              n;
+    ngx_err_t        err;
+    struct kevent    kev;
+    struct timespec  ts;
+
+    if (cv->kq == -1) {
+
+        /*
+         * We have to add the EVFILT_SIGNAL filter in the rfork()ed thread.
+         * Otherwise the thread would not get a signal event.
+         *
+         * However, we have not to open the kqueue in the thread,
+         * it is simply handy do it together.
+         */
+
+        cv->kq = kqueue();
+        if (cv->kq == -1) {
+            ngx_log_error(NGX_LOG_ALERT, cv->log, ngx_errno, "kqueue() failed");
+            return NGX_ERROR;
+        }
+
+        ngx_log_debug2(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                       "cv kq:%d signo:%d", cv->kq, cv->signo);
+
+        kev.ident = cv->signo;
+        kev.filter = EVFILT_SIGNAL;
+        kev.flags = EV_ADD;
+        kev.fflags = 0;
+        kev.data = 0;
+        kev.udata = NULL;
+
+        ts.tv_sec = 0;
+        ts.tv_nsec = 0;
+
+        if (kevent(cv->kq, &kev, 1, NULL, 0, &ts) == -1) {
+            ngx_log_error(NGX_LOG_ALERT, cv->log, ngx_errno, "kevent() failed");
+            return NGX_ERROR;
+        }
+    }
+
+    if (ngx_mutex_unlock(m) == NGX_ERROR) {
+        return NGX_ERROR;
+    }
+
+    ngx_log_debug3(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                   "cv " PTR_FMT " wait, kq:%d, signo:%d",
+                   cv, cv->kq, cv->signo);
+
+    for ( ;; ) {
+        n = kevent(cv->kq, NULL, 0, &kev, 1, NULL);
+
+        ngx_log_debug2(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                       "cv " PTR_FMT " kevent: %d", cv, n);
+
+        if (n == -1) {
+            err = ngx_errno;
+            ngx_log_error((err == NGX_EINTR) ? NGX_LOG_INFO : NGX_LOG_ALERT,
+                          cv->log, ngx_errno,
+                          "kevent() failed while waiting condition variable "
+                          PTR_FMT, cv);
+
+            if (err == NGX_EINTR) {
+                break;
+            }
+
+            return NGX_ERROR;
+        }
+
+        if (n == 0) {
+            ngx_log_error(NGX_LOG_ALERT, cv->log, 0,
+                          "kevent() returned no events "
+                          "while waiting condition variable " PTR_FMT,
+                          cv);
+            continue;
+        }
+
+        if (kev.filter != EVFILT_SIGNAL) {
+            ngx_log_error(NGX_LOG_ALERT, cv->log, 0,
+                          "kevent() returned unexpected events: %d "
+                          "while waiting condition variable " PTR_FMT,
+                          kev.filter, cv);
+            continue;
+        }
+
+        if (kev.ident != (uintptr_t) cv->signo) {
+            ngx_log_error(NGX_LOG_ALERT, cv->log, 0,
+                          "kevent() returned unexpected signal: %d ",
+                          "while waiting condition variable " PTR_FMT,
+                          kev.ident, cv);
+            continue;
+        }
+
+        break;
+    }
+
+    ngx_log_debug1(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                   "cv " PTR_FMT " is waked up", cv);
+
+    if (ngx_mutex_lock(m) == NGX_ERROR) {
+        return NGX_ERROR;
+    }
+
+    return NGX_OK;
+}
+
+
+ngx_int_t ngx_cond_signal(ngx_cond_t *cv)
+{
+    ngx_err_t  err;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                   "cv " PTR_FMT " to signal " PID_T_FMT " %d",
+                   cv, cv->tid, cv->signo);
+
+    if (kill(cv->tid, cv->signo) == -1) {
+
+        err = ngx_errno;
+
+        ngx_log_error(NGX_LOG_ALERT, cv->log, err,
+                      "kill() failed while signaling condition variable "
+                      PTR_FMT, cv);
+
+        if (err == NGX_ESRCH) {
+            cv->tid = -1;
+        }
+
+        return NGX_ERROR;
+    }
+
+    ngx_log_debug1(NGX_LOG_DEBUG_CORE, cv->log, 0,
+                   "cv " PTR_FMT " is signaled", cv);
+
+    return NGX_OK;
+}