Fresh start

1 files changed, 1695 insertions, 0 deletions

diff --git a/jni/ruby/cont.c b/jni/ruby/cont.c
new file mode 100644
index 0000000..d70583a
--- /dev/null
+++ b/jni/ruby/cont.c
@@ -0,0 +1,1695 @@
+/**********************************************************************
+
+  cont.c -
+
+  $Author: nagachika $
+  created at: Thu May 23 09:03:43 2007
+
+  Copyright (C) 2007 Koichi Sasada
+
+**********************************************************************/
+
+#include "internal.h"
+#include "vm_core.h"
+#include "gc.h"
+#include "eval_intern.h"
+
+/* FIBER_USE_NATIVE enables Fiber performance improvement using system
+ * dependent method such as make/setcontext on POSIX system or
+ * CreateFiber() API on Windows.
+ * This hack make Fiber context switch faster (x2 or more).
+ * However, it decrease maximum number of Fiber.  For example, on the
+ * 32bit POSIX OS, ten or twenty thousands Fiber can be created.
+ *
+ * Details is reported in the paper "A Fast Fiber Implementation for Ruby 1.9"
+ * in Proc. of 51th Programming Symposium, pp.21--28 (2010) (in Japanese).
+ */
+
+#if !defined(FIBER_USE_NATIVE)
+# if defined(HAVE_GETCONTEXT) && defined(HAVE_SETCONTEXT)
+#   if 0
+#   elif defined(__NetBSD__)
+/* On our experience, NetBSD doesn't support using setcontext() and pthread
+ * simultaneously.  This is because pthread_self(), TLS and other information
+ * are represented by stack pointer (higher bits of stack pointer).
+ * TODO: check such constraint on configure.
+ */
+#     define FIBER_USE_NATIVE 0
+#   elif defined(__sun)
+/* On Solaris because resuming any Fiber caused SEGV, for some reason.
+ */
+#     define FIBER_USE_NATIVE 0
+#   elif defined(__ia64)
+/* At least, Linux/ia64's getcontext(3) doesn't save register window.
+ */
+#     define FIBER_USE_NATIVE 0
+#   elif defined(__GNU__)
+/* GNU/Hurd doesn't fully support getcontext, setcontext, makecontext
+ * and swapcontext functions. Disabling their usage till support is
+ * implemented. More info at
+ * http://darnassus.sceen.net/~hurd-web/open_issues/glibc/#getcontext
+ */
+#     define FIBER_USE_NATIVE 0
+#   else
+#     define FIBER_USE_NATIVE 1
+#   endif
+# elif defined(_WIN32)
+#   if _WIN32_WINNT >= 0x0400
+/* only when _WIN32_WINNT >= 0x0400 on Windows because Fiber APIs are
+ * supported only such building (and running) environments.
+ * [ruby-dev:41192]
+ */
+#     define FIBER_USE_NATIVE 1
+#   endif
+# endif
+#endif
+#if !defined(FIBER_USE_NATIVE)
+#define FIBER_USE_NATIVE 0
+#endif
+
+#if FIBER_USE_NATIVE
+#ifndef _WIN32
+#include <unistd.h>
+#include <sys/mman.h>
+#include <ucontext.h>
+#endif
+#define RB_PAGE_SIZE (pagesize)
+#define RB_PAGE_MASK (~(RB_PAGE_SIZE - 1))
+static long pagesize;
+#endif /*FIBER_USE_NATIVE*/
+
+#define CAPTURE_JUST_VALID_VM_STACK 1
+
+enum context_type {
+    CONTINUATION_CONTEXT = 0,
+    FIBER_CONTEXT = 1,
+    ROOT_FIBER_CONTEXT = 2
+};
+
+typedef struct rb_context_struct {
+    enum context_type type;
+    int argc;
+    VALUE self;
+    VALUE value;
+    VALUE *vm_stack;
+#ifdef CAPTURE_JUST_VALID_VM_STACK
+    size_t vm_stack_slen;  /* length of stack (head of th->stack) */
+    size_t vm_stack_clen;  /* length of control frames (tail of th->stack) */
+#endif
+    struct {
+	VALUE *stack;
+	VALUE *stack_src;
+	size_t stack_size;
+#ifdef __ia64
+	VALUE *register_stack;
+	VALUE *register_stack_src;
+	int register_stack_size;
+#endif
+    } machine;
+    rb_thread_t saved_thread; /* selected properties of GET_THREAD() (see cont_save_thread) */
+    rb_jmpbuf_t jmpbuf;
+    rb_ensure_entry_t *ensure_array;
+    rb_ensure_list_t *ensure_list;
+} rb_context_t;
+
+enum fiber_status {
+    CREATED,
+    RUNNING,
+    TERMINATED
+};
+
+#if FIBER_USE_NATIVE && !defined(_WIN32)
+#define MAX_MACHINE_STACK_CACHE  10
+static int machine_stack_cache_index = 0;
+typedef struct machine_stack_cache_struct {
+    void *ptr;
+    size_t size;
+} machine_stack_cache_t;
+static machine_stack_cache_t machine_stack_cache[MAX_MACHINE_STACK_CACHE];
+static machine_stack_cache_t terminated_machine_stack;
+#endif
+
+struct rb_fiber_struct {
+    rb_context_t cont;
+    struct rb_fiber_struct *prev;
+    enum fiber_status status;
+    /* If a fiber invokes "transfer",
+     * then this fiber can't "resume" any more after that.
+     * You shouldn't mix "transfer" and "resume".
+     */
+    int transfered;
+
+#if FIBER_USE_NATIVE
+#ifdef _WIN32
+    void *fib_handle;
+#else
+    ucontext_t context;
+    /* Because context.uc_stack.ss_sp and context.uc_stack.ss_size
+     * are not necessarily valid after makecontext() or swapcontext(),
+     * they are saved in these variables for later use.
+     */
+    void *ss_sp;
+    size_t ss_size;
+#endif
+#endif
+};
+
+static const rb_data_type_t cont_data_type, fiber_data_type;
+static VALUE rb_cContinuation;
+static VALUE rb_cFiber;
+static VALUE rb_eFiberError;
+
+#define GetContPtr(obj, ptr)  \
+    TypedData_Get_Struct((obj), rb_context_t, &cont_data_type, (ptr))
+
+#define GetFiberPtr(obj, ptr)  do {\
+    TypedData_Get_Struct((obj), rb_fiber_t, &fiber_data_type, (ptr)); \
+    if (!(ptr)) rb_raise(rb_eFiberError, "uninitialized fiber"); \
+} while (0)
+
+NOINLINE(static VALUE cont_capture(volatile int *stat));
+
+#define THREAD_MUST_BE_RUNNING(th) do { \
+	if (!(th)->tag) rb_raise(rb_eThreadError, "not running thread");	\
+    } while (0)
+
+static void
+cont_mark(void *ptr)
+{
+    RUBY_MARK_ENTER("cont");
+    if (ptr) {
+	rb_context_t *cont = ptr;
+	rb_gc_mark(cont->value);
+	rb_thread_mark(&cont->saved_thread);
+	rb_gc_mark(cont->saved_thread.self);
+
+	if (cont->vm_stack) {
+#ifdef CAPTURE_JUST_VALID_VM_STACK
+	    rb_gc_mark_locations(cont->vm_stack,
+				 cont->vm_stack + cont->vm_stack_slen + cont->vm_stack_clen);
+#else
+	    rb_gc_mark_locations(cont->vm_stack,
+				 cont->vm_stack, cont->saved_thread.stack_size);
+#endif
+	}
+
+	if (cont->machine.stack) {
+	    if (cont->type == CONTINUATION_CONTEXT) {
+		/* cont */
+		rb_gc_mark_locations(cont->machine.stack,
+				     cont->machine.stack + cont->machine.stack_size);
+            }
+            else {
+		/* fiber */
+		rb_thread_t *th;
+                rb_fiber_t *fib = (rb_fiber_t*)cont;
+		GetThreadPtr(cont->saved_thread.self, th);
+		if ((th->fiber != fib) && fib->status == RUNNING) {
+		    rb_gc_mark_locations(cont->machine.stack,
+					 cont->machine.stack + cont->machine.stack_size);
+		}
+	    }
+	}
+#ifdef __ia64
+	if (cont->machine.register_stack) {
+	    rb_gc_mark_locations(cont->machine.register_stack,
+				 cont->machine.register_stack + cont->machine.register_stack_size);
+	}
+#endif
+    }
+    RUBY_MARK_LEAVE("cont");
+}
+
+static void
+cont_free(void *ptr)
+{
+    RUBY_FREE_ENTER("cont");
+    if (ptr) {
+	rb_context_t *cont = ptr;
+	RUBY_FREE_UNLESS_NULL(cont->saved_thread.stack); fflush(stdout);
+#if FIBER_USE_NATIVE
+	if (cont->type == CONTINUATION_CONTEXT) {
+	    /* cont */
+	    ruby_xfree(cont->ensure_array);
+	    RUBY_FREE_UNLESS_NULL(cont->machine.stack);
+	}
+	else {
+	    /* fiber */
+	    rb_fiber_t *fib = (rb_fiber_t*)cont;
+#ifdef _WIN32
+	    if (GET_THREAD()->fiber != fib && cont->type != ROOT_FIBER_CONTEXT) {
+		/* don't delete root fiber handle */
+		rb_fiber_t *fib = (rb_fiber_t*)cont;
+		if (fib->fib_handle) {
+		    DeleteFiber(fib->fib_handle);
+		}
+	    }
+#else /* not WIN32 */
+	    if (GET_THREAD()->fiber != fib) {
+                rb_fiber_t *fib = (rb_fiber_t*)cont;
+                if (fib->ss_sp) {
+                    if (cont->type == ROOT_FIBER_CONTEXT) {
+			rb_bug("Illegal root fiber parameter");
+                    }
+		    munmap((void*)fib->ss_sp, fib->ss_size);
+		}
+	    }
+            else {
+		/* It may reached here when finalize */
+		/* TODO examine whether it is a bug */
+                /* rb_bug("cont_free: release self"); */
+            }
+#endif
+	}
+#else /* not FIBER_USE_NATIVE */
+	ruby_xfree(cont->ensure_array);
+	RUBY_FREE_UNLESS_NULL(cont->machine.stack);
+#endif
+#ifdef __ia64
+	RUBY_FREE_UNLESS_NULL(cont->machine.register_stack);
+#endif
+	RUBY_FREE_UNLESS_NULL(cont->vm_stack);
+
+	/* free rb_cont_t or rb_fiber_t */
+	ruby_xfree(ptr);
+    }
+    RUBY_FREE_LEAVE("cont");
+}
+
+static size_t
+cont_memsize(const void *ptr)
+{
+    const rb_context_t *cont = ptr;
+    size_t size = 0;
+    if (cont) {
+	size = sizeof(*cont);
+	if (cont->vm_stack) {
+#ifdef CAPTURE_JUST_VALID_VM_STACK
+	    size_t n = (cont->vm_stack_slen + cont->vm_stack_clen);
+#else
+	    size_t n = cont->saved_thread.stack_size;
+#endif
+	    size += n * sizeof(*cont->vm_stack);
+	}
+
+	if (cont->machine.stack) {
+	    size += cont->machine.stack_size * sizeof(*cont->machine.stack);
+	}
+#ifdef __ia64
+	if (cont->machine.register_stack) {
+	    size += cont->machine.register_stack_size * sizeof(*cont->machine.register_stack);
+	}
+#endif
+    }
+    return size;
+}
+
+void
+rb_fiber_mark_self(rb_fiber_t *fib)
+{
+    if (fib)
+	rb_gc_mark(fib->cont.self);
+}
+
+static void
+fiber_mark(void *ptr)
+{
+    RUBY_MARK_ENTER("cont");
+    if (ptr) {
+	rb_fiber_t *fib = ptr;
+	rb_fiber_mark_self(fib->prev);
+	cont_mark(&fib->cont);
+    }
+    RUBY_MARK_LEAVE("cont");
+}
+
+static void
+fiber_free(void *ptr)
+{
+    RUBY_FREE_ENTER("fiber");
+    if (ptr) {
+	rb_fiber_t *fib = ptr;
+	if (fib->cont.type != ROOT_FIBER_CONTEXT &&
+	    fib->cont.saved_thread.local_storage) {
+	    st_free_table(fib->cont.saved_thread.local_storage);
+	}
+
+	cont_free(&fib->cont);
+    }
+    RUBY_FREE_LEAVE("fiber");
+}
+
+static size_t
+fiber_memsize(const void *ptr)
+{
+    const rb_fiber_t *fib = ptr;
+    size_t size = 0;
+    if (ptr) {
+	size = sizeof(*fib);
+	if (fib->cont.type != ROOT_FIBER_CONTEXT &&
+	    fib->cont.saved_thread.local_storage != NULL) {
+	    size += st_memsize(fib->cont.saved_thread.local_storage);
+	}
+	size += cont_memsize(&fib->cont);
+    }
+    return size;
+}
+
+VALUE
+rb_obj_is_fiber(VALUE obj)
+{
+    if (rb_typeddata_is_kind_of(obj, &fiber_data_type)) {
+	return Qtrue;
+    }
+    else {
+	return Qfalse;
+    }
+}
+
+static void
+cont_save_machine_stack(rb_thread_t *th, rb_context_t *cont)
+{
+    size_t size;
+
+    SET_MACHINE_STACK_END(&th->machine.stack_end);
+#ifdef __ia64
+    th->machine.register_stack_end = rb_ia64_bsp();
+#endif
+
+    if (th->machine.stack_start > th->machine.stack_end) {
+	size = cont->machine.stack_size = th->machine.stack_start - th->machine.stack_end;
+	cont->machine.stack_src = th->machine.stack_end;
+    }
+    else {
+	size = cont->machine.stack_size = th->machine.stack_end - th->machine.stack_start;
+	cont->machine.stack_src = th->machine.stack_start;
+    }
+
+    if (cont->machine.stack) {
+	REALLOC_N(cont->machine.stack, VALUE, size);
+    }
+    else {
+	cont->machine.stack = ALLOC_N(VALUE, size);
+    }
+
+    FLUSH_REGISTER_WINDOWS;
+    MEMCPY(cont->machine.stack, cont->machine.stack_src, VALUE, size);
+
+#ifdef __ia64
+    rb_ia64_flushrs();
+    size = cont->machine.register_stack_size = th->machine.register_stack_end - th->machine.register_stack_start;
+    cont->machine.register_stack_src = th->machine.register_stack_start;
+    if (cont->machine.register_stack) {
+	REALLOC_N(cont->machine.register_stack, VALUE, size);
+    }
+    else {
+	cont->machine.register_stack = ALLOC_N(VALUE, size);
+    }
+
+    MEMCPY(cont->machine.register_stack, cont->machine.register_stack_src, VALUE, size);
+#endif
+}
+
+static const rb_data_type_t cont_data_type = {
+    "continuation",
+    {cont_mark, cont_free, cont_memsize,},
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+static inline void
+cont_save_thread(rb_context_t *cont, rb_thread_t *th)
+{
+    rb_thread_t *sth = &cont->saved_thread;
+
+    /* save thread context */
+    sth->stack = th->stack;
+    sth->stack_size = th->stack_size;
+    sth->local_storage = th->local_storage;
+    sth->cfp = th->cfp;
+    sth->safe_level = th->safe_level;
+    sth->raised_flag = th->raised_flag;
+    sth->state = th->state;
+    sth->status = th->status;
+    sth->tag = th->tag;
+    sth->protect_tag = th->protect_tag;
+    sth->errinfo = th->errinfo;
+    sth->first_proc = th->first_proc;
+    sth->root_lep = th->root_lep;
+    sth->root_svar = th->root_svar;
+    sth->ensure_list = th->ensure_list;
+
+    sth->trace_arg = th->trace_arg;
+
+    /* saved_thread->machine.stack_(start|end) should be NULL */
+    /* because it may happen GC afterward */
+    sth->machine.stack_start = 0;
+    sth->machine.stack_end = 0;
+#ifdef __ia64
+    sth->machine.register_stack_start = 0;
+    sth->machine.register_stack_end = 0;
+#endif
+}
+
+static void
+cont_init(rb_context_t *cont, rb_thread_t *th)
+{
+    /* save thread context */
+    cont_save_thread(cont, th);
+    cont->saved_thread.self = th->self;
+    cont->saved_thread.machine.stack_maxsize = th->machine.stack_maxsize;
+    cont->saved_thread.fiber = th->fiber;
+    cont->saved_thread.local_storage = 0;
+    cont->saved_thread.local_storage_recursive_hash = Qnil;
+    cont->saved_thread.local_storage_recursive_hash_for_trace = Qnil;
+}
+
+static rb_context_t *
+cont_new(VALUE klass)
+{
+    rb_context_t *cont;
+    volatile VALUE contval;
+    rb_thread_t *th = GET_THREAD();
+
+    THREAD_MUST_BE_RUNNING(th);
+    contval = TypedData_Make_Struct(klass, rb_context_t, &cont_data_type, cont);
+    cont->self = contval;
+    cont_init(cont, th);
+    return cont;
+}
+
+static VALUE
+cont_capture(volatile int *stat)
+{
+    rb_context_t *cont;
+    rb_thread_t *th = GET_THREAD();
+    volatile VALUE contval;
+
+    THREAD_MUST_BE_RUNNING(th);
+    rb_vm_stack_to_heap(th);
+    cont = cont_new(rb_cContinuation);
+    contval = cont->self;
+
+#ifdef CAPTURE_JUST_VALID_VM_STACK
+    cont->vm_stack_slen = th->cfp->sp - th->stack;
+    cont->vm_stack_clen = th->stack + th->stack_size - (VALUE*)th->cfp;
+    cont->vm_stack = ALLOC_N(VALUE, cont->vm_stack_slen + cont->vm_stack_clen);
+    MEMCPY(cont->vm_stack, th->stack, VALUE, cont->vm_stack_slen);
+    MEMCPY(cont->vm_stack + cont->vm_stack_slen, (VALUE*)th->cfp, VALUE, cont->vm_stack_clen);
+#else
+    cont->vm_stack = ALLOC_N(VALUE, th->stack_size);
+    MEMCPY(cont->vm_stack, th->stack, VALUE, th->stack_size);
+#endif
+    cont->saved_thread.stack = 0;
+
+    cont_save_machine_stack(th, cont);
+
+    /* backup ensure_list to array for search in another context */
+    {
+	rb_ensure_list_t *p;
+	int size = 0;
+	rb_ensure_entry_t *entry;
+	for (p=th->ensure_list; p; p=p->next)
+	    size++;
+	entry = cont->ensure_array = ALLOC_N(rb_ensure_entry_t,size+1);
+	for (p=th->ensure_list; p; p=p->next) {
+	    if (!p->entry.marker)
+		p->entry.marker = rb_ary_tmp_new(0); /* dummy object */
+	    *entry++ = p->entry;
+	}
+	entry->marker = 0;
+    }
+
+    if (ruby_setjmp(cont->jmpbuf)) {
+	volatile VALUE value;
+
+	VAR_INITIALIZED(cont);
+	value = cont->value;
+	if (cont->argc == -1) rb_exc_raise(value);
+	cont->value = Qnil;
+	*stat = 1;
+	return value;
+    }
+    else {
+	*stat = 0;
+	return contval;
+    }
+}
+
+static inline void
+cont_restore_thread(rb_context_t *cont)
+{
+    rb_thread_t *th = GET_THREAD(), *sth = &cont->saved_thread;
+
+    /* restore thread context */
+    if (cont->type == CONTINUATION_CONTEXT) {
+	/* continuation */
+	rb_fiber_t *fib;
+
+	th->fiber = sth->fiber;
+	fib = th->fiber ? th->fiber : th->root_fiber;
+
+	if (fib) {
+	    th->stack_size = fib->cont.saved_thread.stack_size;
+	    th->stack = fib->cont.saved_thread.stack;
+	}
+#ifdef CAPTURE_JUST_VALID_VM_STACK
+	MEMCPY(th->stack, cont->vm_stack, VALUE, cont->vm_stack_slen);
+	MEMCPY(th->stack + sth->stack_size - cont->vm_stack_clen,
+	       cont->vm_stack + cont->vm_stack_slen, VALUE, cont->vm_stack_clen);
+#else
+	MEMCPY(th->stack, cont->vm_stack, VALUE, sth->stack_size);
+#endif
+    }
+    else {
+	/* fiber */
+	th->stack = sth->stack;
+	th->stack_size = sth->stack_size;
+	th->local_storage = sth->local_storage;
+	th->local_storage_recursive_hash = sth->local_storage_recursive_hash;
+	th->local_storage_recursive_hash_for_trace = sth->local_storage_recursive_hash_for_trace;
+	th->fiber = (rb_fiber_t*)cont;
+    }
+
+    th->cfp = sth->cfp;
+    th->safe_level = sth->safe_level;
+    th->raised_flag = sth->raised_flag;
+    th->state = sth->state;
+    th->status = sth->status;
+    th->tag = sth->tag;
+    th->protect_tag = sth->protect_tag;
+    th->errinfo = sth->errinfo;
+    th->first_proc = sth->first_proc;
+    th->root_lep = sth->root_lep;
+    th->root_svar = sth->root_svar;
+    th->ensure_list = sth->ensure_list;
+
+}
+
+#if FIBER_USE_NATIVE
+#ifdef _WIN32
+static void
+fiber_set_stack_location(void)
+{
+    rb_thread_t *th = GET_THREAD();
+    VALUE *ptr;
+
+    SET_MACHINE_STACK_END(&ptr);
+    th->machine.stack_start = (void*)(((VALUE)ptr & RB_PAGE_MASK) + STACK_UPPER((void *)&ptr, 0, RB_PAGE_SIZE));
+}
+
+static VOID CALLBACK
+fiber_entry(void *arg)
+{
+    fiber_set_stack_location();
+    rb_fiber_start();
+}
+#else /* _WIN32 */
+
+/*
+ * FreeBSD require a first (i.e. addr) argument of mmap(2) is not NULL
+ * if MAP_STACK is passed.
+ * http://www.FreeBSD.org/cgi/query-pr.cgi?pr=158755
+ */
+#if defined(MAP_STACK) && !defined(__FreeBSD__) && !defined(__FreeBSD_kernel__)
+#define FIBER_STACK_FLAGS (MAP_PRIVATE | MAP_ANON | MAP_STACK)
+#else
+#define FIBER_STACK_FLAGS (MAP_PRIVATE | MAP_ANON)
+#endif
+
+static char*
+fiber_machine_stack_alloc(size_t size)
+{
+    char *ptr;
+
+    if (machine_stack_cache_index > 0) {
+	if (machine_stack_cache[machine_stack_cache_index - 1].size == (size / sizeof(VALUE))) {
+	    ptr = machine_stack_cache[machine_stack_cache_index - 1].ptr;
+	    machine_stack_cache_index--;
+	    machine_stack_cache[machine_stack_cache_index].ptr = NULL;
+	    machine_stack_cache[machine_stack_cache_index].size = 0;
+	}
+	else{
+            /* TODO handle multiple machine stack size */
+	    rb_bug("machine_stack_cache size is not canonicalized");
+	}
+    }
+    else {
+	void *page;
+	STACK_GROW_DIR_DETECTION;
+
+	errno = 0;
+	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, FIBER_STACK_FLAGS, -1, 0);
+	if (ptr == MAP_FAILED) {
+	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber: %s", strerror(errno));
+	}
+
+	/* guard page setup */
+	page = ptr + STACK_DIR_UPPER(size - RB_PAGE_SIZE, 0);
+	if (mprotect(page, RB_PAGE_SIZE, PROT_NONE) < 0) {
+	    rb_raise(rb_eFiberError, "mprotect failed");
+	}
+    }
+
+    return ptr;
+}
+#endif
+
+static void
+fiber_initialize_machine_stack_context(rb_fiber_t *fib, size_t size)
+{
+    rb_thread_t *sth = &fib->cont.saved_thread;
+
+#ifdef _WIN32
+    fib->fib_handle = CreateFiberEx(size - 1, size, 0, fiber_entry, NULL);
+    if (!fib->fib_handle) {
+	/* try to release unnecessary fibers & retry to create */
+	rb_gc();
+	fib->fib_handle = CreateFiberEx(size - 1, size, 0, fiber_entry, NULL);
+	if (!fib->fib_handle) {
+	    rb_raise(rb_eFiberError, "can't create fiber");
+	}
+    }
+    sth->machine.stack_maxsize = size;
+#else /* not WIN32 */
+    ucontext_t *context = &fib->context;
+    char *ptr;
+    STACK_GROW_DIR_DETECTION;
+
+    getcontext(context);
+    ptr = fiber_machine_stack_alloc(size);
+    context->uc_link = NULL;
+    context->uc_stack.ss_sp = ptr;
+    context->uc_stack.ss_size = size;
+    fib->ss_sp = ptr;
+    fib->ss_size = size;
+    makecontext(context, rb_fiber_start, 0);
+    sth->machine.stack_start = (VALUE*)(ptr + STACK_DIR_UPPER(0, size));
+    sth->machine.stack_maxsize = size - RB_PAGE_SIZE;
+#endif
+#ifdef __ia64
+    sth->machine.register_stack_maxsize = sth->machine.stack_maxsize;
+#endif
+}
+
+NOINLINE(static void fiber_setcontext(rb_fiber_t *newfib, rb_fiber_t *oldfib));
+
+static void
+fiber_setcontext(rb_fiber_t *newfib, rb_fiber_t *oldfib)
+{
+    rb_thread_t *th = GET_THREAD(), *sth = &newfib->cont.saved_thread;
+
+    if (newfib->status != RUNNING) {
+	fiber_initialize_machine_stack_context(newfib, th->vm->default_params.fiber_machine_stack_size);
+    }
+
+    /* restore thread context */
+    cont_restore_thread(&newfib->cont);
+    th->machine.stack_maxsize = sth->machine.stack_maxsize;
+    if (sth->machine.stack_end && (newfib != oldfib)) {
+	rb_bug("fiber_setcontext: sth->machine.stack_end has non zero value");
+    }
+
+    /* save  oldfib's machine stack */
+    if (oldfib->status != TERMINATED) {
+	STACK_GROW_DIR_DETECTION;
+	SET_MACHINE_STACK_END(&th->machine.stack_end);
+	if (STACK_DIR_UPPER(0, 1)) {
+	    oldfib->cont.machine.stack_size = th->machine.stack_start - th->machine.stack_end;
+	    oldfib->cont.machine.stack = th->machine.stack_end;
+	}
+	else {
+	    oldfib->cont.machine.stack_size = th->machine.stack_end - th->machine.stack_start;
+	    oldfib->cont.machine.stack = th->machine.stack_start;
+	}
+    }
+    /* exchange machine_stack_start between oldfib and newfib */
+    oldfib->cont.saved_thread.machine.stack_start = th->machine.stack_start;
+    th->machine.stack_start = sth->machine.stack_start;
+    /* oldfib->machine.stack_end should be NULL */
+    oldfib->cont.saved_thread.machine.stack_end = 0;
+#ifndef _WIN32
+    if (!newfib->context.uc_stack.ss_sp && th->root_fiber != newfib) {
+	rb_bug("non_root_fiber->context.uc_stac.ss_sp should not be NULL");
+    }
+#endif
+
+    /* swap machine context */
+#ifdef _WIN32
+    SwitchToFiber(newfib->fib_handle);
+#else
+    swapcontext(&oldfib->context, &newfib->context);
+#endif
+}
+#endif
+
+NOINLINE(NORETURN(static void cont_restore_1(rb_context_t *)));
+
+static void
+cont_restore_1(rb_context_t *cont)
+{
+    cont_restore_thread(cont);
+
+    /* restore machine stack */
+#ifdef _M_AMD64
+    {
+	/* workaround for x64 SEH */
+	jmp_buf buf;
+	setjmp(buf);
+	((_JUMP_BUFFER*)(&cont->jmpbuf))->Frame =
+	    ((_JUMP_BUFFER*)(&buf))->Frame;
+    }
+#endif
+    if (cont->machine.stack_src) {
+	FLUSH_REGISTER_WINDOWS;
+	MEMCPY(cont->machine.stack_src, cont->machine.stack,
+		VALUE, cont->machine.stack_size);
+    }
+
+#ifdef __ia64
+    if (cont->machine.register_stack_src) {
+	MEMCPY(cont->machine.register_stack_src, cont->machine.register_stack,
+	       VALUE, cont->machine.register_stack_size);
+    }
+#endif
+
+    ruby_longjmp(cont->jmpbuf, 1);
+}
+
+NORETURN(NOINLINE(static void cont_restore_0(rb_context_t *, VALUE *)));
+
+#ifdef __ia64
+#define C(a) rse_##a##0, rse_##a##1, rse_##a##2, rse_##a##3, rse_##a##4
+#define E(a) rse_##a##0= rse_##a##1= rse_##a##2= rse_##a##3= rse_##a##4
+static volatile int C(a), C(b), C(c), C(d), C(e);
+static volatile int C(f), C(g), C(h), C(i), C(j);
+static volatile int C(k), C(l), C(m), C(n), C(o);
+static volatile int C(p), C(q), C(r), C(s), C(t);
+#if 0
+{/* the above lines make cc-mode.el confused so much */}
+#endif
+int rb_dummy_false = 0;
+NORETURN(NOINLINE(static void register_stack_extend(rb_context_t *, VALUE *, VALUE *)));
+static void
+register_stack_extend(rb_context_t *cont, VALUE *vp, VALUE *curr_bsp)
+{
+    if (rb_dummy_false) {
+        /* use registers as much as possible */
+        E(a) = E(b) = E(c) = E(d) = E(e) =
+        E(f) = E(g) = E(h) = E(i) = E(j) =
+        E(k) = E(l) = E(m) = E(n) = E(o) =
+        E(p) = E(q) = E(r) = E(s) = E(t) = 0;
+        E(a) = E(b) = E(c) = E(d) = E(e) =
+        E(f) = E(g) = E(h) = E(i) = E(j) =
+        E(k) = E(l) = E(m) = E(n) = E(o) =
+        E(p) = E(q) = E(r) = E(s) = E(t) = 0;
+    }
+    if (curr_bsp < cont->machine.register_stack_src+cont->machine.register_stack_size) {
+        register_stack_extend(cont, vp, (VALUE*)rb_ia64_bsp());
+    }
+    cont_restore_0(cont, vp);
+}
+#undef C
+#undef E
+#endif
+
+static void
+cont_restore_0(rb_context_t *cont, VALUE *addr_in_prev_frame)
+{
+    if (cont->machine.stack_src) {
+#ifdef HAVE_ALLOCA
+#define STACK_PAD_SIZE 1
+#else
+#define STACK_PAD_SIZE 1024
+#endif
+	VALUE space[STACK_PAD_SIZE];
+
+#if !STACK_GROW_DIRECTION
+	if (addr_in_prev_frame > &space[0]) {
+	    /* Stack grows downward */
+#endif
+#if STACK_GROW_DIRECTION <= 0
+	    volatile VALUE *const end = cont->machine.stack_src;
+	    if (&space[0] > end) {
+# ifdef HAVE_ALLOCA
+		volatile VALUE *sp = ALLOCA_N(VALUE, &space[0] - end);
+		space[0] = *sp;
+# else
+		cont_restore_0(cont, &space[0]);
+# endif
+	    }
+#endif
+#if !STACK_GROW_DIRECTION
+	}
+	else {
+	    /* Stack grows upward */
+#endif
+#if STACK_GROW_DIRECTION >= 0
+	    volatile VALUE *const end = cont->machine.stack_src + cont->machine.stack_size;
+	    if (&space[STACK_PAD_SIZE] < end) {
+# ifdef HAVE_ALLOCA
+		volatile VALUE *sp = ALLOCA_N(VALUE, end - &space[STACK_PAD_SIZE]);
+		space[0] = *sp;
+# else
+		cont_restore_0(cont, &space[STACK_PAD_SIZE-1]);
+# endif
+	    }
+#endif
+#if !STACK_GROW_DIRECTION
+	}
+#endif
+    }
+    cont_restore_1(cont);
+}
+#ifdef __ia64
+#define cont_restore_0(cont, vp) register_stack_extend((cont), (vp), (VALUE*)rb_ia64_bsp())
+#endif
+
+/*
+ *  Document-class: Continuation
+ *
+ *  Continuation objects are generated by Kernel#callcc,
+ *  after having +require+d <i>continuation</i>. They hold
+ *  a return address and execution context, allowing a nonlocal return
+ *  to the end of the <code>callcc</code> block from anywhere within a
+ *  program. Continuations are somewhat analogous to a structured
+ *  version of C's <code>setjmp/longjmp</code> (although they contain
+ *  more state, so you might consider them closer to threads).
+ *
+ *  For instance:
+ *
+ *     require "continuation"
+ *     arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
+ *     callcc{|cc| $cc = cc}
+ *     puts(message = arr.shift)
+ *     $cc.call unless message =~ /Max/
+ *
+ *  <em>produces:</em>
+ *
+ *     Freddie
+ *     Herbie
+ *     Ron
+ *     Max
+ *
+ *  This (somewhat contrived) example allows the inner loop to abandon
+ *  processing early:
+ *
+ *     require "continuation"
+ *     callcc {|cont|
+ *       for i in 0..4
+ *         print "\n#{i}: "
+ *         for j in i*5...(i+1)*5
+ *           cont.call() if j == 17
+ *           printf "%3d", j
+ *         end
+ *       end
+ *     }
+ *     puts
+ *
+ *  <em>produces:</em>
+ *
+ *     0:   0  1  2  3  4
+ *     1:   5  6  7  8  9
+ *     2:  10 11 12 13 14
+ *     3:  15 16
+ */
+
+/*
+ *  call-seq:
+ *     callcc {|cont| block }   ->  obj
+ *
+ *  Generates a Continuation object, which it passes to
+ *  the associated block. You need to <code>require
+ *  'continuation'</code> before using this method. Performing a
+ *  <em>cont</em><code>.call</code> will cause the #callcc
+ *  to return (as will falling through the end of the block). The
+ *  value returned by the #callcc is the value of the
+ *  block, or the value passed to <em>cont</em><code>.call</code>. See
+ *  class Continuation for more details. Also see
+ *  Kernel#throw for an alternative mechanism for
+ *  unwinding a call stack.
+ */
+
+static VALUE
+rb_callcc(VALUE self)
+{
+    volatile int called;
+    volatile VALUE val = cont_capture(&called);
+
+    if (called) {
+	return val;
+    }
+    else {
+	return rb_yield(val);
+    }
+}
+
+static VALUE
+make_passing_arg(int argc, const VALUE *argv)
+{
+    switch (argc) {
+      case 0:
+	return Qnil;
+      case 1:
+	return argv[0];
+      default:
+	return rb_ary_new4(argc, argv);
+    }
+}
+
+/* CAUTION!! : Currently, error in rollback_func is not supported  */
+/* same as rb_protect if set rollback_func to NULL */
+void
+ruby_register_rollback_func_for_ensure(VALUE (*ensure_func)(ANYARGS), VALUE (*rollback_func)(ANYARGS))
+{
+    st_table **table_p = &GET_VM()->ensure_rollback_table;
+    if (UNLIKELY(*table_p == NULL)) {
+	*table_p = st_init_numtable();
+    }
+    st_insert(*table_p, (st_data_t)ensure_func, (st_data_t)rollback_func);
+}
+
+static inline VALUE
+lookup_rollback_func(VALUE (*ensure_func)(ANYARGS))
+{
+    st_table *table = GET_VM()->ensure_rollback_table;
+    st_data_t val;
+    if (table && st_lookup(table, (st_data_t)ensure_func, &val))
+	return (VALUE) val;
+    return Qundef;
+}
+
+
+static inline void
+rollback_ensure_stack(VALUE self,rb_ensure_list_t *current,rb_ensure_entry_t *target)
+{
+    rb_ensure_list_t *p;
+    rb_ensure_entry_t *entry;
+    size_t i;
+    size_t cur_size;
+    size_t target_size;
+    size_t base_point;
+    VALUE (*func)(ANYARGS);
+
+    cur_size = 0;
+    for (p=current; p; p=p->next)
+	cur_size++;
+    target_size = 0;
+    for (entry=target; entry->marker; entry++)
+	target_size++;
+
+    /* search common stack point */
+    p = current;
+    base_point = cur_size;
+    while (base_point) {
+	if (target_size >= base_point &&
+	    p->entry.marker == target[target_size - base_point].marker)
+	    break;
+	base_point --;
+	p = p->next;
+    }
+
+    /* rollback function check */
+    for (i=0; i < target_size - base_point; i++) {
+	if (!lookup_rollback_func(target[i].e_proc)) {
+	    rb_raise(rb_eRuntimeError, "continuation called from out of critical rb_ensure scope");
+	}
+    }
+    /* pop ensure stack */
+    while (cur_size > base_point) {
+	/* escape from ensure block */
+	(*current->entry.e_proc)(current->entry.data2);
+	current = current->next;
+	cur_size--;
+    }
+    /* push ensure stack */
+    while (i--) {
+	func = (VALUE (*)(ANYARGS)) lookup_rollback_func(target[i].e_proc);
+	if ((VALUE)func != Qundef) {
+	    (*func)(target[i].data2);
+	}
+    }
+}
+
+/*
+ *  call-seq:
+ *     cont.call(args, ...)
+ *     cont[args, ...]
+ *
+ *  Invokes the continuation. The program continues from the end of the
+ *  <code>callcc</code> block. If no arguments are given, the original
+ *  <code>callcc</code> returns <code>nil</code>. If one argument is
+ *  given, <code>callcc</code> returns it. Otherwise, an array
+ *  containing <i>args</i> is returned.
+ *
+ *     callcc {|cont|  cont.call }           #=> nil
+ *     callcc {|cont|  cont.call 1 }         #=> 1
+ *     callcc {|cont|  cont.call 1, 2, 3 }   #=> [1, 2, 3]
+ */
+
+static VALUE
+rb_cont_call(int argc, VALUE *argv, VALUE contval)
+{
+    rb_context_t *cont;
+    rb_thread_t *th = GET_THREAD();
+    GetContPtr(contval, cont);
+
+    if (cont->saved_thread.self != th->self) {
+	rb_raise(rb_eRuntimeError, "continuation called across threads");
+    }
+    if (cont->saved_thread.protect_tag != th->protect_tag) {
+	rb_raise(rb_eRuntimeError, "continuation called across stack rewinding barrier");
+    }
+    if (cont->saved_thread.fiber) {
+	if (th->fiber != cont->saved_thread.fiber) {
+	    rb_raise(rb_eRuntimeError, "continuation called across fiber");
+	}
+    }
+    rollback_ensure_stack(contval, th->ensure_list, cont->ensure_array);
+
+    cont->argc = argc;
+    cont->value = make_passing_arg(argc, argv);
+
+    /* restore `tracing' context. see [Feature #4347] */
+    th->trace_arg = cont->saved_thread.trace_arg;
+
+    cont_restore_0(cont, &contval);
+    return Qnil; /* unreachable */
+}
+
+/*********/
+/* fiber */
+/*********/
+
+/*
+ *  Document-class: Fiber
+ *
+ *  Fibers are primitives for implementing light weight cooperative
+ *  concurrency in Ruby. Basically they are a means of creating code blocks
+ *  that can be paused and resumed, much like threads. The main difference
+ *  is that they are never preempted and that the scheduling must be done by
+ *  the programmer and not the VM.
+ *
+ *  As opposed to other stackless light weight concurrency models, each fiber
+ *  comes with a small 4KB stack. This enables the fiber to be paused from deeply
+ *  nested function calls within the fiber block.
+ *
+ *  When a fiber is created it will not run automatically. Rather it must be
+ *  be explicitly asked to run using the <code>Fiber#resume</code> method.
+ *  The code running inside the fiber can give up control by calling
+ *  <code>Fiber.yield</code> in which case it yields control back to caller
+ *  (the caller of the <code>Fiber#resume</code>).
+ *
+ *  Upon yielding or termination the Fiber returns the value of the last
+ *  executed expression
+ *
+ *  For instance:
+ *
+ *    fiber = Fiber.new do
+ *      Fiber.yield 1
+ *      2
+ *    end
+ *
+ *    puts fiber.resume
+ *    puts fiber.resume
+ *    puts fiber.resume
+ *
+ *  <em>produces</em>
+ *
+ *    1
+ *    2
+ *    FiberError: dead fiber called
+ *
+ *  The <code>Fiber#resume</code> method accepts an arbitrary number of
+ *  parameters, if it is the first call to <code>resume</code> then they
+ *  will be passed as block arguments. Otherwise they will be the return
+ *  value of the call to <code>Fiber.yield</code>
+ *
+ *  Example:
+ *
+ *    fiber = Fiber.new do |first|
+ *      second = Fiber.yield first + 2
+ *    end
+ *
+ *    puts fiber.resume 10
+ *    puts fiber.resume 14
+ *    puts fiber.resume 18
+ *
+ *  <em>produces</em>
+ *
+ *    12
+ *    14
+ *    FiberError: dead fiber called
+ *
+ */
+
+static const rb_data_type_t fiber_data_type = {
+    "fiber",
+    {fiber_mark, fiber_free, fiber_memsize,},
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+static VALUE
+fiber_alloc(VALUE klass)
+{
+    return TypedData_Wrap_Struct(klass, &fiber_data_type, 0);
+}
+
+static rb_fiber_t*
+fiber_t_alloc(VALUE fibval)
+{
+    rb_fiber_t *fib;
+    rb_thread_t *th = GET_THREAD();
+
+    if (DATA_PTR(fibval) != 0) {
+	rb_raise(rb_eRuntimeError, "cannot initialize twice");
+    }
+
+    THREAD_MUST_BE_RUNNING(th);
+    fib = ZALLOC(rb_fiber_t);
+    fib->cont.self = fibval;
+    fib->cont.type = FIBER_CONTEXT;
+    cont_init(&fib->cont, th);
+    fib->prev = NULL;
+    fib->status = CREATED;
+
+    DATA_PTR(fibval) = fib;
+
+    return fib;
+}
+
+static VALUE
+fiber_init(VALUE fibval, VALUE proc)
+{
+    rb_fiber_t *fib = fiber_t_alloc(fibval);
+    rb_context_t *cont = &fib->cont;
+    rb_thread_t *th = &cont->saved_thread;
+    rb_thread_t *cth = GET_THREAD();
+
+    /* initialize cont */
+    cont->vm_stack = 0;
+
+    th->stack = 0;
+    th->stack_size = 0;
+
+    th->stack_size = cth->vm->default_params.fiber_vm_stack_size / sizeof(VALUE);
+    th->stack = ALLOC_N(VALUE, th->stack_size);
+
+    th->cfp = (void *)(th->stack + th->stack_size);
+    th->cfp--;
+    th->cfp->pc = 0;
+    th->cfp->sp = th->stack + 1;
+#if VM_DEBUG_BP_CHECK
+    th->cfp->bp_check = 0;
+#endif
+    th->cfp->ep = th->stack;
+    *th->cfp->ep = VM_ENVVAL_BLOCK_PTR(0);
+    th->cfp->self = Qnil;
+    th->cfp->klass = Qnil;
+    th->cfp->flag = 0;
+    th->cfp->iseq = 0;
+    th->cfp->proc = 0;
+    th->cfp->block_iseq = 0;
+    th->cfp->me = 0;
+    th->tag = 0;
+    th->local_storage = st_init_numtable();
+    th->local_storage_recursive_hash = Qnil;
+    th->local_storage_recursive_hash_for_trace = Qnil;
+
+    th->first_proc = proc;
+
+#if !FIBER_USE_NATIVE
+    MEMCPY(&cont->jmpbuf, &cth->root_jmpbuf, rb_jmpbuf_t, 1);
+#endif
+
+    return fibval;
+}
+
+/* :nodoc: */
+static VALUE
+rb_fiber_init(VALUE fibval)
+{
+    return fiber_init(fibval, rb_block_proc());
+}
+
+VALUE
+rb_fiber_new(VALUE (*func)(ANYARGS), VALUE obj)
+{
+    return fiber_init(fiber_alloc(rb_cFiber), rb_proc_new(func, obj));
+}
+
+static void rb_fiber_terminate(rb_fiber_t *fib);
+
+void
+rb_fiber_start(void)
+{
+    rb_thread_t *th = GET_THREAD();
+    rb_fiber_t *fib = th->fiber;
+    rb_proc_t *proc;
+    int state;
+
+    TH_PUSH_TAG(th);
+    if ((state = EXEC_TAG()) == 0) {
+	rb_context_t *cont = &VAR_FROM_MEMORY(fib)->cont;
+	int argc;
+	const VALUE *argv, args = cont->value;
+	GetProcPtr(cont->saved_thread.first_proc, proc);
+	argv = (argc = cont->argc) > 1 ? RARRAY_CONST_PTR(args) : &args;
+	cont->value = Qnil;
+	th->errinfo = Qnil;
+	th->root_lep = rb_vm_ep_local_ep(proc->block.ep);
+	th->root_svar = Qnil;
+
+	fib->status = RUNNING;
+	cont->value = rb_vm_invoke_proc(th, proc, argc, argv, 0);
+    }
+    TH_POP_TAG();
+
+    if (state) {
+	if (state == TAG_RAISE || state == TAG_FATAL) {
+	    rb_threadptr_pending_interrupt_enque(th, th->errinfo);
+	}
+	else {
+	    VALUE err = rb_vm_make_jump_tag_but_local_jump(state, th->errinfo);
+	    if (!NIL_P(err))
+		rb_threadptr_pending_interrupt_enque(th, err);
+	}
+	RUBY_VM_SET_INTERRUPT(th);
+    }
+
+    rb_fiber_terminate(fib);
+    rb_bug("rb_fiber_start: unreachable");
+}
+
+static rb_fiber_t *
+root_fiber_alloc(rb_thread_t *th)
+{
+    rb_fiber_t *fib;
+    /* no need to allocate vm stack */
+    fib = fiber_t_alloc(fiber_alloc(rb_cFiber));
+    fib->cont.type = ROOT_FIBER_CONTEXT;
+#if FIBER_USE_NATIVE
+#ifdef _WIN32
+    fib->fib_handle = ConvertThreadToFiber(0);
+#endif
+#endif
+    fib->status = RUNNING;
+
+    return fib;
+}
+
+static inline rb_fiber_t*
+fiber_current(void)
+{
+    rb_thread_t *th = GET_THREAD();
+    if (th->fiber == 0) {
+	/* save root */
+	rb_fiber_t *fib = root_fiber_alloc(th);
+	th->root_fiber = th->fiber = fib;
+    }
+    return th->fiber;
+}
+
+static inline rb_fiber_t*
+return_fiber(void)
+{
+    rb_fiber_t *fib = fiber_current();
+    rb_fiber_t *prev = fib->prev;
+
+    if (!prev) {
+	rb_fiber_t *root_fiber = GET_THREAD()->root_fiber;
+
+	if (root_fiber == fib) {
+	    rb_raise(rb_eFiberError, "can't yield from root fiber");
+	}
+	return root_fiber;
+    }
+    else {
+	fib->prev = NULL;
+	return prev;
+    }
+}
+
+VALUE
+rb_fiber_current(void)
+{
+    return fiber_current()->cont.self;
+}
+
+static inline VALUE
+fiber_store(rb_fiber_t *next_fib, rb_thread_t *th)
+{
+    rb_fiber_t *fib;
+
+    if (th->fiber) {
+	fib = th->fiber;
+	cont_save_thread(&fib->cont, th);
+    }
+    else {
+	/* create current fiber */
+	fib = root_fiber_alloc(th);
+	th->root_fiber = th->fiber = fib;
+    }
+
+#if FIBER_USE_NATIVE
+    fiber_setcontext(next_fib, fib);
+    /* restored */
+#ifndef _WIN32
+    if (terminated_machine_stack.ptr) {
+	if (machine_stack_cache_index < MAX_MACHINE_STACK_CACHE) {
+	    machine_stack_cache[machine_stack_cache_index].ptr = terminated_machine_stack.ptr;
+	    machine_stack_cache[machine_stack_cache_index].size = terminated_machine_stack.size;
+	    machine_stack_cache_index++;
+	}
+	else {
+	    if (terminated_machine_stack.ptr != fib->cont.machine.stack) {
+		munmap((void*)terminated_machine_stack.ptr, terminated_machine_stack.size * sizeof(VALUE));
+	    }
+	    else {
+		rb_bug("terminated fiber resumed");
+	    }
+	}
+	terminated_machine_stack.ptr = NULL;
+	terminated_machine_stack.size = 0;
+    }
+#endif /* not _WIN32 */
+    fib = th->fiber;
+    if (fib->cont.argc == -1) rb_exc_raise(fib->cont.value);
+    return fib->cont.value;
+
+#else /* FIBER_USE_NATIVE */
+    cont_save_machine_stack(th, &fib->cont);
+    if (ruby_setjmp(fib->cont.jmpbuf)) {
+	/* restored */
+	fib = th->fiber;
+	if (fib->cont.argc == -1) rb_exc_raise(fib->cont.value);
+	if (next_fib->cont.value == Qundef) {
+	    cont_restore_0(&next_fib->cont, &next_fib->cont.value);
+	    rb_bug("rb_fiber_resume: unreachable");
+	}
+	return fib->cont.value;
+    }
+    else {
+	VALUE undef = Qundef;
+	cont_restore_0(&next_fib->cont, &undef);
+	rb_bug("rb_fiber_resume: unreachable");
+    }
+#endif /* FIBER_USE_NATIVE */
+}
+
+static inline VALUE
+fiber_switch(rb_fiber_t *fib, int argc, const VALUE *argv, int is_resume)
+{
+    VALUE value;
+    rb_context_t *cont = &fib->cont;
+    rb_thread_t *th = GET_THREAD();
+
+    if (th->fiber == fib) {
+	/* ignore fiber context switch
+         * because destination fiber is same as current fiber
+	 */
+	return make_passing_arg(argc, argv);
+    }
+
+    if (cont->saved_thread.self != th->self) {
+	rb_raise(rb_eFiberError, "fiber called across threads");
+    }
+    else if (cont->saved_thread.protect_tag != th->protect_tag) {
+	rb_raise(rb_eFiberError, "fiber called across stack rewinding barrier");
+    }
+    else if (fib->status == TERMINATED) {
+	value = rb_exc_new2(rb_eFiberError, "dead fiber called");
+
+	if (th->fiber->status != TERMINATED) rb_exc_raise(value);
+
+	/* th->fiber is also dead => switch to root fiber */
+	/* (this means we're being called from rb_fiber_terminate, */
+	/* and the terminated fiber's return_fiber() is already dead) */
+	cont = &th->root_fiber->cont;
+	cont->argc = -1;
+	cont->value = value;
+#if FIBER_USE_NATIVE
+	fiber_setcontext(th->root_fiber, th->fiber);
+#else
+	cont_restore_0(cont, &value);
+#endif
+	/* unreachable */
+    }
+
+    if (is_resume) {
+	fib->prev = fiber_current();
+    }
+    else {
+	/* restore `tracing' context. see [Feature #4347] */
+	th->trace_arg = cont->saved_thread.trace_arg;
+    }
+
+    cont->argc = argc;
+    cont->value = make_passing_arg(argc, argv);
+
+    value = fiber_store(fib, th);
+    RUBY_VM_CHECK_INTS(th);
+
+    return value;
+}
+
+VALUE
+rb_fiber_transfer(VALUE fibval, int argc, const VALUE *argv)
+{
+    rb_fiber_t *fib;
+    GetFiberPtr(fibval, fib);
+    return fiber_switch(fib, argc, argv, 0);
+}
+
+static void
+rb_fiber_terminate(rb_fiber_t *fib)
+{
+    VALUE value = fib->cont.value;
+    fib->status = TERMINATED;
+#if FIBER_USE_NATIVE && !defined(_WIN32)
+    /* Ruby must not switch to other thread until storing terminated_machine_stack */
+    terminated_machine_stack.ptr = fib->ss_sp;
+    terminated_machine_stack.size = fib->ss_size / sizeof(VALUE);
+    fib->ss_sp = NULL;
+    fib->context.uc_stack.ss_sp = NULL;
+    fib->cont.machine.stack = NULL;
+    fib->cont.machine.stack_size = 0;
+#endif
+    fiber_switch(return_fiber(), 1, &value, 0);
+}
+
+VALUE
+rb_fiber_resume(VALUE fibval, int argc, const VALUE *argv)
+{
+    rb_fiber_t *fib;
+    GetFiberPtr(fibval, fib);
+
+    if (fib->prev != 0 || fib->cont.type == ROOT_FIBER_CONTEXT) {
+	rb_raise(rb_eFiberError, "double resume");
+    }
+    if (fib->transfered != 0) {
+	rb_raise(rb_eFiberError, "cannot resume transferred Fiber");
+    }
+
+    return fiber_switch(fib, argc, argv, 1);
+}
+
+VALUE
+rb_fiber_yield(int argc, const VALUE *argv)
+{
+    return fiber_switch(return_fiber(), argc, argv, 0);
+}
+
+void
+rb_fiber_reset_root_local_storage(VALUE thval)
+{
+    rb_thread_t *th;
+
+    GetThreadPtr(thval, th);
+    if (th->root_fiber && th->root_fiber != th->fiber) {
+	th->local_storage = th->root_fiber->cont.saved_thread.local_storage;
+    }
+}
+
+/*
+ *  call-seq:
+ *     fiber.alive? -> true or false
+ *
+ *  Returns true if the fiber can still be resumed (or transferred
+ *  to). After finishing execution of the fiber block this method will
+ *  always return false. You need to <code>require 'fiber'</code>
+ *  before using this method.
+ */
+VALUE
+rb_fiber_alive_p(VALUE fibval)
+{
+    rb_fiber_t *fib;
+    GetFiberPtr(fibval, fib);
+    return fib->status != TERMINATED ? Qtrue : Qfalse;
+}
+
+/*
+ *  call-seq:
+ *     fiber.resume(args, ...) -> obj
+ *
+ *  Resumes the fiber from the point at which the last <code>Fiber.yield</code>
+ *  was called, or starts running it if it is the first call to
+ *  <code>resume</code>. Arguments passed to resume will be the value of
+ *  the <code>Fiber.yield</code> expression or will be passed as block
+ *  parameters to the fiber's block if this is the first <code>resume</code>.
+ *
+ *  Alternatively, when resume is called it evaluates to the arguments passed
+ *  to the next <code>Fiber.yield</code> statement inside the fiber's block
+ *  or to the block value if it runs to completion without any
+ *  <code>Fiber.yield</code>
+ */
+static VALUE
+rb_fiber_m_resume(int argc, VALUE *argv, VALUE fib)
+{
+    return rb_fiber_resume(fib, argc, argv);
+}
+
+/*
+ *  call-seq:
+ *     fiber.transfer(args, ...) -> obj
+ *
+ *  Transfer control to another fiber, resuming it from where it last
+ *  stopped or starting it if it was not resumed before. The calling
+ *  fiber will be suspended much like in a call to
+ *  <code>Fiber.yield</code>. You need to <code>require 'fiber'</code>
+ *  before using this method.
+ *
+ *  The fiber which receives the transfer call is treats it much like
+ *  a resume call. Arguments passed to transfer are treated like those
+ *  passed to resume.
+ *
+ *  You cannot resume a fiber that transferred control to another one.
+ *  This will cause a double resume error. You need to transfer control
+ *  back to this fiber before it can yield and resume.
+ *
+ *  Example:
+ *
+ *    fiber1 = Fiber.new do
+ *      puts "In Fiber 1"
+ *      Fiber.yield
+ *    end
+ *
+ *    fiber2 = Fiber.new do
+ *      puts "In Fiber 2"
+ *      fiber1.transfer
+ *      puts "Never see this message"
+ *    end
+ *
+ *    fiber3 = Fiber.new do
+ *      puts "In Fiber 3"
+ *    end
+ *
+ *    fiber2.resume
+ *    fiber3.resume
+ *
+ *  <em>produces</em>
+ *
+ *    In fiber 2
+ *    In fiber 1
+ *    In fiber 3
+ *
+ */
+static VALUE
+rb_fiber_m_transfer(int argc, VALUE *argv, VALUE fibval)
+{
+    rb_fiber_t *fib;
+    GetFiberPtr(fibval, fib);
+    fib->transfered = 1;
+    return fiber_switch(fib, argc, argv, 0);
+}
+
+/*
+ *  call-seq:
+ *     Fiber.yield(args, ...) -> obj
+ *
+ *  Yields control back to the context that resumed the fiber, passing
+ *  along any arguments that were passed to it. The fiber will resume
+ *  processing at this point when <code>resume</code> is called next.
+ *  Any arguments passed to the next <code>resume</code> will be the
+ *  value that this <code>Fiber.yield</code> expression evaluates to.
+ */
+static VALUE
+rb_fiber_s_yield(int argc, VALUE *argv, VALUE klass)
+{
+    return rb_fiber_yield(argc, argv);
+}
+
+/*
+ *  call-seq:
+ *     Fiber.current() -> fiber
+ *
+ *  Returns the current fiber. You need to <code>require 'fiber'</code>
+ *  before using this method. If you are not running in the context of
+ *  a fiber this method will return the root fiber.
+ */
+static VALUE
+rb_fiber_s_current(VALUE klass)
+{
+    return rb_fiber_current();
+}
+
+
+
+/*
+ *  Document-class: FiberError
+ *
+ *  Raised when an invalid operation is attempted on a Fiber, in
+ *  particular when attempting to call/resume a dead fiber,
+ *  attempting to yield from the root fiber, or calling a fiber across
+ *  threads.
+ *
+ *     fiber = Fiber.new{}
+ *     fiber.resume #=> nil
+ *     fiber.resume #=> FiberError: dead fiber called
+ */
+
+void
+Init_Cont(void)
+{
+#if FIBER_USE_NATIVE
+    rb_thread_t *th = GET_THREAD();
+
+#ifdef _WIN32
+    SYSTEM_INFO info;
+    GetSystemInfo(&info);
+    pagesize = info.dwPageSize;
+#else /* not WIN32 */
+    pagesize = sysconf(_SC_PAGESIZE);
+#endif
+    SET_MACHINE_STACK_END(&th->machine.stack_end);
+#endif
+
+    rb_cFiber = rb_define_class("Fiber", rb_cObject);
+    rb_define_alloc_func(rb_cFiber, fiber_alloc);
+    rb_eFiberError = rb_define_class("FiberError", rb_eStandardError);
+    rb_define_singleton_method(rb_cFiber, "yield", rb_fiber_s_yield, -1);
+    rb_define_method(rb_cFiber, "initialize", rb_fiber_init, 0);
+    rb_define_method(rb_cFiber, "resume", rb_fiber_m_resume, -1);
+}
+
+RUBY_SYMBOL_EXPORT_BEGIN
+
+void
+ruby_Init_Continuation_body(void)
+{
+    rb_cContinuation = rb_define_class("Continuation", rb_cObject);
+    rb_undef_alloc_func(rb_cContinuation);
+    rb_undef_method(CLASS_OF(rb_cContinuation), "new");
+    rb_define_method(rb_cContinuation, "call", rb_cont_call, -1);
+    rb_define_method(rb_cContinuation, "[]", rb_cont_call, -1);
+    rb_define_global_function("callcc", rb_callcc, 0);
+}
+
+void
+ruby_Init_Fiber_as_Coroutine(void)
+{
+    rb_define_method(rb_cFiber, "transfer", rb_fiber_m_transfer, -1);
+    rb_define_method(rb_cFiber, "alive?", rb_fiber_alive_p, 0);
+    rb_define_singleton_method(rb_cFiber, "current", rb_fiber_s_current, 0);
+}
+
+RUBY_SYMBOL_EXPORT_END