Solve some lock ordering

src/syscall/process.rs

@@ -36,13 +36,11 @@ pub fn exit_this_context(excp: Option<syscall::Exception>, token: &mut CleanLock
     let context_lock = context::current();
     {
         let mut context = context_lock.write(token.token());
-        // let (context, mut token) = context.token_split();
+        let (context, mut token) = context.token_split();
         close_files = Arc::try_unwrap(mem::take(&mut context.files))
             .map_or_else(|_| FdTbl::new(), RwLock::into_inner);
-        // TODO: Lock ordering violation
-        let mut token = unsafe { CleanLockToken::new() };
         addrspace_opt = context
-            .set_addr_space(None, token.downgrade())
+            .set_addr_space(None, token)
             .and_then(|a| Arc::try_unwrap(a).ok());
         drop(mem::replace(&mut context.syscall_head, SyscallFrame::Dummy));
         drop(mem::replace(&mut context.syscall_tail, SyscallFrame::Dummy));