fiber: introduce fiber_o:info() and fiber_o:csw()

If you want to get information or get csw (Context SWitch) of some fiber
you need to call fiber.info(), but it creates table with information about
all the fibers. This patch introduces fiber_object:info() and
fiber_object:csw() - functions to solve this problem.

Closes #5799

@TarantoolBot document
Title: introduce fiber_object:info() and fiber_object:csw()
```
-- fiber_object:info() is the same as fiber.info(), but show information only
about one alive fiber.
-- fiber_object:csw() show csw (Context SWitch) of alive fiber.
```

changelogs/unreleased/gh-5799-add-info-to-fiber-object.md

+## feature/lua/fiber
+
+* Introduce `fiber_object:info()` to get `info` from fiber. Works as `require(fiber).info()` but only for one fiber.
+* Introduce `fiber_object:csw()` to get `csw` from fiber (gh-5799).

src/lua/fiber.c

@@ -263,13 +263,10 @@ fiber_backtrace_cb(int frameno, void *frameret, const char *func, size_t offset,
 #endif
 
 static int
-lbox_fiber_statof(struct fiber *f, void *cb_ctx, bool backtrace)
+lbox_fiber_statof_map(struct fiber *f, void *cb_ctx, bool backtrace)
 {
 	struct lua_State *L = (struct lua_State *) cb_ctx;
 
-	luaL_pushuint64(L, f->fid);
-	lua_newtable(L);
-
 	lua_pushliteral(L, "name");
 	lua_pushstring(L, fiber_name(f));
 	lua_settable(L, -3);
@@ -313,6 +310,16 @@ lbox_fiber_statof(struct fiber *f, void *cb_ctx, bool backtrace)
 		lua_settable(L, -3);
 #endif /* ENABLE_BACKTRACE */
 	}
+	return 0;
+}
+
+static int
+lbox_fiber_statof(struct fiber *f, void *cb_ctx, bool backtrace)
+{
+	struct lua_State *L = cb_ctx;
+	luaL_pushuint64(L, f->fid);
+	lua_newtable(L);
+	lbox_fiber_statof_map(f, cb_ctx, backtrace);
 	lua_settable(L, -3);
 	return 0;
 }
@@ -406,14 +413,10 @@ lbox_fiber_top_disable(struct lua_State *L)
 }
 #endif /* ENABLE_FIBER_TOP */
 
-/**
- * Return fiber statistics.
- */
-static int
-lbox_fiber_info(struct lua_State *L)
-{
 #ifdef ENABLE_BACKTRACE
-	bool do_backtrace = true;
+bool
+lbox_do_backtrace(struct lua_State *L)
+{
 	if (lua_istable(L, 1)) {
 		lua_pushstring(L, "backtrace");
 		lua_gettable(L, 1);
@@ -423,9 +426,21 @@ lbox_fiber_info(struct lua_State *L)
 			lua_gettable(L, 1);
 		}
 		if (!lua_isnil(L, -1))
-			do_backtrace = lua_toboolean(L, -1);
+			return lua_toboolean(L, -1);
 		lua_pop(L, 1);
 	}
+	return true;
+}
+#endif /* ENABLE_BACKTRACE */
+
+/**
+ * Return fiber statistics.
+ */
+static int
+lbox_fiber_info(struct lua_State *L)
+{
+#ifdef ENABLE_BACKTRACE
+	bool do_backtrace = lbox_do_backtrace(L);
 	if (do_backtrace) {
 		lua_newtable(L);
 		fiber_stat(lbox_fiber_statof_bt, L);
@@ -527,6 +542,17 @@ lbox_fiber_new(struct lua_State *L)
 	return 1;
 }
 
+static struct fiber *
+lbox_get_fiber(struct lua_State *L)
+{
+	if (lua_gettop(L) != 0) {
+		uint64_t *fid = luaL_checkudata(L, 1, fiberlib_name);
+		return fiber_find(*fid);
+	} else {
+		return fiber();
+	}
+}
+
 /**
  * Get fiber status.
  * This follows the rules of Lua coroutine.status() function:
@@ -540,16 +566,9 @@ lbox_fiber_new(struct lua_State *L)
 static int
 lbox_fiber_status(struct lua_State *L)
 {
-	struct fiber *f;
-	if (lua_gettop(L)) {
-		uint64_t fid = *(uint64_t *)
-			luaL_checkudata(L, 1, fiberlib_name);
-		f = fiber_find(fid);
-	} else {
-		f = fiber();
-	}
+	struct fiber *f = lbox_get_fiber(L);
 	const char *status;
-	if (f == NULL || f->fid == 0) {
+	if (f == NULL) {
 		/* This fiber is dead. */
 		status = "dead";
 	} else if (f == fiber()) {
@@ -563,6 +582,42 @@ lbox_fiber_status(struct lua_State *L)
 	return 1;
 }
 
+/**
+ * Get fiber info: number of context switches, backtrace, id,
+ * total memory, used memory.
+ */
+static int
+lbox_fiber_object_info(struct lua_State *L)
+{
+	struct fiber *f = lbox_get_fiber(L);
+	if (f == NULL)
+		luaL_error(L, "the fiber is dead");
+#ifdef ENABLE_BACKTRACE
+	bool do_backtrace = lbox_do_backtrace(L);
+	if (do_backtrace) {
+		lua_newtable(L);
+		lbox_fiber_statof_map(f, L, true);
+	} else
+#endif /* ENABLE_BACKTRACE */
+	{
+		lua_newtable(L);
+		lbox_fiber_statof_map(f, L, false);
+	}
+	return 1;
+}
+
+static int
+lbox_fiber_csw(struct lua_State *L)
+{
+	struct fiber *f = lbox_get_fiber(L);
+	if (f == NULL) {
+		luaL_error(L, "the fiber is dead");
+	} else {
+		lua_pushinteger(L, f->csw);
+	}
+	return 1;
+}
+
 /**
  * Get or set fiber name.
  * With no arguments, gets or sets the current fiber
@@ -857,6 +912,8 @@ static const struct luaL_Reg lbox_fiber_meta [] = {
 	{"name", lbox_fiber_name},
 	{"cancel", lbox_fiber_cancel},
 	{"status", lbox_fiber_status},
+	{"info", lbox_fiber_object_info},
+	{"csw", lbox_fiber_csw},
 	{"testcancel", lbox_fiber_testcancel},
 	{"__serialize", lbox_fiber_serialize},
 	{"__tostring", lbox_fiber_tostring},

test/app/gh-5799-fiber-info.result

+-- test-run result file version 2
+test_run = require('test_run').new()
+ | ---
+ | ...
+fiber = require('fiber')
+ | ---
+ | ...
+json = require('json')
+ | ---
+ | ...
+
+function yielder(n) for i=1, n do fiber.yield() end end
+ | ---
+ | ...
+
+csw_check_counter = 0
+ | ---
+ | ...
+fibers = {}
+ | ---
+ | ...
+
+test_run:cmd('setopt delimiter ";"')
+ | ---
+ | - true
+ | ...
+for i=1,100 do
+    fibers[i] = fiber.new(function()
+        local start_csw = fiber.info()[fiber.self():id()].csw
+        for j=1,10 do
+            fiber.yield()
+            if j + start_csw == fiber.self():csw() and
+               j + start_csw == fiber.self():info().csw then
+                csw_check_counter = csw_check_counter + 1
+            end
+        end
+    end)
+    fibers[i]:set_joinable(true)
+end;
+ | ---
+ | ...
+for i=1,100 do
+    fibers[i]:join()
+end;
+ | ---
+ | ...
+test_run:cmd('setopt delimiter ""');
+ | ---
+ | - true
+ | ...
+csw_check_counter
+ | ---
+ | - 1000
+ | ...
+
+cond = fiber.cond()
+ | ---
+ | ...
+running = fiber.create(function() cond:wait() end)
+ | ---
+ | ...
+json.encode(running:info()) == json.encode(fiber.info()[running:id()])
+ | ---
+ | - true
+ | ...
+cond:signal()
+ | ---
+ | ...
+dead = fiber.create(function() end)
+ | ---
+ | ...
+
+dead:csw()
+ | ---
+ | - error: the fiber is dead
+ | ...
+dead:info()
+ | ---
+ | - error: the fiber is dead
+ | ...

test/app/gh-5799-fiber-info.test.lua

+test_run = require('test_run').new()
+fiber = require('fiber')
+json = require('json')
+
+function yielder(n) for i=1, n do fiber.yield() end end
+
+csw_check_counter = 0
+fibers = {}
+
+test_run:cmd('setopt delimiter ";"')
+for i=1,100 do
+    fibers[i] = fiber.new(function()
+        local start_csw = fiber.info()[fiber.self():id()].csw
+        for j=1,10 do
+            fiber.yield()
+            if j + start_csw == fiber.self():csw() and
+               j + start_csw == fiber.self():info().csw then
+                csw_check_counter = csw_check_counter + 1
+            end
+        end
+    end)
+    fibers[i]:set_joinable(true)
+end;
+for i=1,100 do
+    fibers[i]:join()
+end;
+test_run:cmd('setopt delimiter ""');
+csw_check_counter
+
+cond = fiber.cond()
+running = fiber.create(function() cond:wait() end)
+json.encode(running:info()) == json.encode(fiber.info()[running:id()])
+cond:signal()
+dead = fiber.create(function() end)
+
+dead:csw()
+dead:info()