switched queue to pre-allocating all messages
diff --git a/aos/linux_code/ipc_lib/queue.h b/aos/linux_code/ipc_lib/queue.h
index e1baaef..70f3943 100644
--- a/aos/linux_code/ipc_lib/queue.h
+++ b/aos/linux_code/ipc_lib/queue.h
@@ -147,9 +147,9 @@
 
   Mutex pool_lock_;
   size_t msg_length_;  // sizeof(each message) including the header
-  int mem_length_;  // the max number of messages that will ever be allocated
   int messages_used_;
-  int pool_length_;  // the number of allocated messages
+  // The number of messages in pool_.
+  int pool_length_;
   MessageHeader **pool_;  // array of pointers to messages
 
   // Actually frees the given message.