diff --git a/core/tarantool_lua.m b/core/tarantool_lua.m
index c5dde48b60e1c29d5f503bc084fe4f4a93739388..1ed40a189688d56670e64c6580427b3053825852 100644
--- a/core/tarantool_lua.m
+++ b/core/tarantool_lua.m
@@ -207,30 +207,30 @@ static const struct luaL_reg boxlib[] = {
/** {{{ box.fiber Lua library: access to Tarantool/Box fibers
*
* Each fiber can be running, suspended or dead.
- * It can also be attached or detached.
- * All fibers are part of the fiber registry,
- * box.fiber. This registry can be searched either by
+ * A fiber is created (box.fiber.create()) suspended.
+ * It can be started with box.fiber.resume(), yield
+ * the control back with box.fiber.yield() end
+ * with return or just by reaching the end of the
+ * function.
+ *
+ * A fiber can also be attached or detached.
+ * An attached fiber is a child of the creator,
+ * and is running only if the creator has called
+ * box.fiber.resume(). A detached fiber is a child of
+ * Tarntool/Box internal 'sched' fiber, and is gets
+ * scheduled only if there is a libev event associated
+ * with it.
+ * To detach, a running fiber must invoke box.fiber.detach().
+ * A detached fiber loses connection with its parent
+ * forever.
+ *
+ * All fibers are part of the fiber registry, box.fiber.
+ * This registry can be searched either by
* fiber id (fid), which is numeric, or by fiber name,
* which is a string. If there is more than one
* fiber with the given name, the first fiber that
* matches is returned.
*
- * A new fiber can also be created from Lua, with
- * fiber.create(). The fiber
- * is created suspended, and is thus "attached"
- * to the creator. The creator can invoke the suspended
- * fiber with fiber.resume(), and the invoked fiber
- * can yield control back to the caller with fiber.yield().
- *
- * An active fiber, however, may choose to "detach"
- * from the caller, and become part of the main Tarantool/Box
- * loop. This is what all internal Tarantool/Box fibers
- * are -- detached. To "detach" from its creator,
- * a running fiber can use fiber.detach(). A detached
- * fiber becomes attached to the internal "sched"
- * fiber, and can not be attached back to its original
- * creator.
- *
* Once fiber chunk is done or calls "return",
* the fiber is considered dead. Its carcass is put into
* fiber pool, and can be reused when another fiber is
@@ -241,20 +241,73 @@ static const struct luaL_reg boxlib[] = {
* only if the runaway fiber is calling fiber.testcancel()
* once in a while. Most box.* hooks, such as box.delete()
* or box.update(), are calling fiber.testcancel().
+ *
* Thus a runaway fiber can really only become cuckoo
* if it does a lot of computations and doesn't check
* whether it's been cancelled (just don't do that).
+ *
+ * The other potential problem comes from detached
+ * fibers which never get scheduled, because are subscribed
+ * or get no events. Such morphing fibers can be killed
+ * with box.fiber.cancel(), since box.fiber.cancel()
+ * sends an asynchronous wakeup event to the fiber.
*/
static const char *fiberlib_name = "box.fiber";
-struct fiber *
+/** Push a userdata for the given fiber onto Lua stack. */
+static void
+lbox_pushfiber(struct lua_State *L, struct fiber *f)
+{
+ /*
+ * Use 'memoize' pattern and keep a single userdata for
+ * the given fiber.
+ */
+ luaL_getmetatable(L, fiberlib_name);
+ int top = lua_gettop(L);
+ lua_getfield(L, -1, "memoize");
+ if (lua_isnil(L, -1)) { /* first access - instantiate memoize */
+ lua_pop(L, 1); /* pop the nil */
+ lua_newtable(L); /* create memoize table */
+ lua_newtable(L); /* and a metatable */
+ lua_pushstring(L, "kv"); /* weak keys and values */
+ lua_setfield(L, -2, "__mode"); /* pops 'kv' */
+ lua_setmetatable(L, -2); /* pops the metatable */
+ lua_setfield(L, -2, "memoize"); /* assigns and pops memoize */
+ lua_getfield(L, -1, "memoize"); /* gets memoize back. */
+ assert(! lua_isnil(L, -1));
+ }
+ /* Find out whether the fiber is already in the memoize table. */
+ lua_pushlightuserdata(L, f);
+ lua_gettable(L, -2);
+ if (lua_isnil(L, -1)) { /* no userdata for fiber created so far */
+ lua_pop(L, 1); /* pop the nil */
+ lua_pushlightuserdata(L, f); /* push the key back */
+ /* create a new userdata */
+ void **ptr = lua_newuserdata(L, sizeof(void *));
+ *ptr = f;
+ luaL_getmetatable(L, fiberlib_name);
+ lua_setmetatable(L, -2);
+ lua_settable(L, -3); /* memoize it */
+ lua_pushlightuserdata(L, f);
+ lua_gettable(L, -2); /* get it back */
+ }
+ /*
+ * Here we have a userdata on top of the stack and
+ * possibly some garbage just under the top. Move the
+ * result to the beginning of the stack and clear the rest.
+ */
+ lua_replace(L, top); /* moves the current top to the old top */
+ lua_settop(L, top); /* clears everything after the old top */
+}
+
+static struct fiber *
lbox_checkfiber(struct lua_State *L, int index)
{
return *(void **) luaL_checkudata(L, index, fiberlib_name);
}
-int
+static int
lbox_fiber_id(struct lua_State *L)
{
struct fiber *f = lbox_checkfiber(L, 1);
@@ -267,7 +320,7 @@ lbox_fiber_id(struct lua_State *L)
*
* Only the current fiber can be made to sleep.
*/
-int
+static int
lbox_fiber_sleep(struct lua_State *L)
{
if (! lua_isnumber(L, 1) || lua_gettop(L) != 1)
@@ -277,20 +330,17 @@ lbox_fiber_sleep(struct lua_State *L)
return 0;
}
-int
+static int
lbox_fiber_self(struct lua_State *L)
{
- void **ptr = lua_newuserdata(L, sizeof(void *));
- luaL_getmetatable(L, fiberlib_name);
- lua_setmetatable(L, -2);
- *ptr = fiber;
+ lbox_pushfiber(L, fiber);
return 1;
}
/** Running and suspended fibers can be cancelled.
* Zombie fibers can't.
*/
-int
+static int
lbox_fiber_cancel(struct lua_State *L)
{
struct fiber *f = lbox_checkfiber(L, 1);
@@ -306,7 +356,7 @@ lbox_fiber_cancel(struct lua_State *L)
* throw an exception if this is the case.
*/
-int
+static int
lbox_fiber_testcancel(struct lua_State *L)
{
if (lua_gettop(L) != 0)
@@ -331,8 +381,9 @@ static const struct luaL_reg fiberlib[] = {
/* }}} */
/*
- * lua_tostring does no use __tostring metamethod, and it has
- * to be called if we want to print Lua userdata correctly.
+ * This function exists because lua_tostring does not use
+ * __tostring metamethod, and this metamethod has to be used
+ * if we want to print Lua userdata correctly.
*/
const char *
tarantool_lua_tostring(struct lua_State *L, int index)
@@ -381,10 +432,10 @@ tarantool_lua_printstack(struct lua_State *L, struct tbuf *out)
* administrative command.
*
* Note: administrative console output must be YAML-compatible.
- * If this is * done automatically, the result is ugly, so we
- * don't do it. A creator of Lua procedures has to do it herself.
- * Best we can do here is to add a trailing \r\n if it's
- * forgotten.
+ * If this is done automatically, the result is ugly, so we
+ * don't do it. Creators of Lua procedures have to do it
+ * themselves. Best we can do here is to add a trailing
+ * \r\n if it's forgotten.
*/
static int
lbox_print(struct lua_State *L)
@@ -508,7 +559,8 @@ tarantool_lua(struct lua_State *L,
* Check if the given literal is a number/boolean or string
* literal. A string literal needs quotes.
*/
-static bool is_string(const char *str)
+static bool
+is_string(const char *str)
{
if (strcmp(str, "true") == 0 || strcmp(str, "false") == 0)
return false;
@@ -524,7 +576,8 @@ static bool is_string(const char *str)
* as functional to convert the given configuration to a Lua
* table and export the table into Lua.
*/
-void tarantool_lua_load_cfg(struct lua_State *L, struct tarantool_cfg *cfg)
+void
+tarantool_lua_load_cfg(struct lua_State *L, struct tarantool_cfg *cfg)
{
luaL_Buffer b;
char *key, *value;
diff --git a/test/box/lua.result b/test/box/lua.result
index 0c28179dbdaef6295cd75d07609c381d1c33e71e..5ad20fae0032aeee5d7754e75e357bf5b363ecb6 100644
--- a/test/box/lua.result
+++ b/test/box/lua.result
@@ -553,3 +553,10 @@ lua f:id(), box.fiber.self():id()
- 110
- 110
...
+lua g = box.fiber.self()
+---
+...
+lua f==g
+---
+ - true
+...
diff --git a/test/box/lua.test b/test/box/lua.test
index e887edfc9dbc8a6dcca15f03eb01f765453d1e81..d9242622cf6ca98d168780aa41fed9663a73fae3 100644
--- a/test/box/lua.test
+++ b/test/box/lua.test
@@ -152,3 +152,5 @@ exec admin "lua box.fiber.cancel(f)"
exec admin "lua f:id(), box.fiber.self():id()"
exec admin "lua box.fiber.cancel(box.fiber.self())"
exec admin "lua f:id(), box.fiber.self():id()"
+exec admin "lua g = box.fiber.self()"
+exec admin "lua f==g"