diff --git a/lualib/skynet.lua b/lualib/skynet.lua
index 7e5115cb..f9d934c3 100644
--- a/lualib/skynet.lua
+++ b/lualib/skynet.lua
@@ -583,11 +583,11 @@ function skynet.mqlen()
 	return tonumber(c.command "MQLEN")
 end
 
-function skynet.task(f)
+function skynet.task(ret)
 	local t = 0
-	for _,co in pairs(session_id_coroutine) do
-		if f then
-			f(debug.traceback(co))
+	for session,co in pairs(session_id_coroutine) do
+		if ret then
+			ret[session] = debug.traceback(co)
 		end
 		t = t + 1
 	end
diff --git a/lualib/skynet/debug.lua b/lualib/skynet/debug.lua
index bb5877fe..c8f51f0b 100644
--- a/lualib/skynet/debug.lua
+++ b/lualib/skynet/debug.lua
@@ -27,7 +27,7 @@ end
 
 function dbgcmd.TASK()
 	local task = {}
-	skynet.task(function(info) table.insert(task, info) end)
+	skynet.task(task)
 	skynet.ret(skynet.pack(task))
 end