diff --git a/src/emqx_cm.erl b/src/emqx_cm.erl
index a7e7f6356..9e3edf0b7 100644
--- a/src/emqx_cm.erl
+++ b/src/emqx_cm.erl
@@ -133,26 +133,22 @@ handle_call(Req, _From, State) ->
     emqx_logger:error("[CM] Unexpected request: ~p", [Req]),
     {reply, ignore, State}.
 
-handle_cast({notify, {registered, ClientId, Pid}},
-            State = #state{client_pmon = PMon}) ->
-    {noreply, State#state{client_pmon = PMon:monitor(Pid, ClientId)}};
+handle_cast({notify, {registered, ClientId, Pid}}, State = #state{client_pmon = PMon}) ->
+    {noreply, State#state{client_pmon = emqx_pmon:monitor(Pid, ClientId, PMon)}};
 
-handle_cast({notify, {unregistered, _ClientId, Pid}},
-            State = #state{client_pmon = PMon}) ->
-    {noreply, State#state{client_pmon = PMon:demonitor(Pid)}};
+handle_cast({notify, {unregistered, _ClientId, Pid}}, State = #state{client_pmon = PMon}) ->
+    {noreply, State#state{client_pmon = emqx_pmon:demonitor(Pid, PMon)}};
 
 handle_cast(Msg, State) ->
     emqx_logger:error("[CM] Unexpected msg: ~p", [Msg]),
     {noreply, State}.
 
-handle_info({'DOWN', _MRef, process, DownPid, _Reason},
-            State = #state{client_pmon = PMon}) ->
-    case PMon:find(DownPid) of
-        undefined ->
-            {noreply, State};
-        ClientId ->
+handle_info({'DOWN', _MRef, process, DownPid, _Reason}, State = #state{client_pmon = PMon}) ->
+    case emqx_pmon:find(DownPid, PMon) of
+        undefined -> {noreply, State};
+        ClientId  ->
             unregister_client({ClientId, DownPid}),
-            {noreply, State#state{client_pmon = PMon:erase(DownPid)}}
+            {noreply, State#state{client_pmon = emqx_pmon:erase(DownPid, PMon)}}
     end;
 
 handle_info(Info, State) ->
diff --git a/src/emqx_pmon.erl b/src/emqx_pmon.erl
index bcb4ae537..6af403a2d 100644
--- a/src/emqx_pmon.erl
+++ b/src/emqx_pmon.erl
@@ -35,10 +35,9 @@ monitor(Pid, PM) ->
 
 monitor(Pid, Val, PM = {?MODULE, [M]}) ->
     case maps:is_key(Pid, M) of
-        true -> PM;
-        false ->
-            Ref = erlang:monitor(process, Pid),
-            {?MODULE, [maps:put(Pid, {Ref, Val}, M)]}
+        true  -> PM;
+        false -> Ref = erlang:monitor(process, Pid),
+                 {?MODULE, [maps:put(Pid, {Ref, Val}, M)]}
     end.
 
 -spec(demonitor(pid(), pmon()) -> pmon()).
@@ -48,8 +47,7 @@ demonitor(Pid, PM = {?MODULE, [M]}) ->
             %% Don't flush
             _ = erlang:demonitor(Ref),
             {?MODULE, [maps:remove(Pid, M)]};
-        error ->
-            PM
+        error -> PM
     end.
 
 -spec(find(pid(), pmon()) -> undefined | term()).
diff --git a/src/emqx_shared_sub.erl b/src/emqx_shared_sub.erl
index f4f0ecf8e..6825ca8d0 100644
--- a/src/emqx_shared_sub.erl
+++ b/src/emqx_shared_sub.erl
@@ -116,7 +116,7 @@ init([]) ->
 init_monitors() ->
     mnesia:foldl(
       fun(#shared_subscription{subpid = SubPid}, Mon) ->
-          Mon:monitor(SubPid)
+          emqx_pmon:monitor(SubPid, Mon)
       end, emqx_pmon:new(), ?TAB).
 
 handle_call(Req, _From, State) ->
@@ -124,7 +124,7 @@ handle_call(Req, _From, State) ->
     {reply, ignore, State}.
 
 handle_cast({monitor, SubPid}, State= #state{pmon = PMon}) ->
-    {noreply, update_stats(State#state{pmon = PMon:monitor(SubPid)})};
+    {noreply, update_stats(State#state{pmon = emqx_pmon:monitor(SubPid, PMon)})};
 
 handle_cast(Msg, State) ->
     emqx_logger:error("[Shared] Unexpected msg: ~p", [Msg]),
@@ -132,11 +132,11 @@ handle_cast(Msg, State) ->
 
 handle_info({mnesia_table_event, {write, NewRecord, _}}, State = #state{pmon = PMon}) ->
     #shared_subscription{subpid = SubPid} = NewRecord,
-    {noreply, update_stats(State#state{pmon = PMon:monitor(SubPid)})};
+    {noreply, update_stats(State#state{pmon = emqx_pmon:monitor(SubPid, PMon)})};
 
 handle_info({mnesia_table_event, {delete_object, OldRecord, _}}, State = #state{pmon = PMon}) ->
     #shared_subscription{subpid = SubPid} = OldRecord,
-    {noreply, update_stats(State#state{pmon = PMon:demonitor(SubPid)})};
+    {noreply, update_stats(State#state{pmon = emqx_pmon:demonitor(SubPid, PMon)})};
 
 handle_info({mnesia_table_event, _Event}, State) ->
     {noreply, State};
@@ -144,7 +144,7 @@ handle_info({mnesia_table_event, _Event}, State) ->
 handle_info({'DOWN', _MRef, process, SubPid, _Reason}, State = #state{pmon = PMon}) ->
     emqx_logger:info("Shared subscription down: ~p", [SubPid]),
     mnesia:async_dirty(fun cleanup_down/1, [SubPid]),
-    {noreply, update_stats(State#state{pmon = PMon:erase(SubPid)})};
+    {noreply, update_stats(State#state{pmon = emqx_pmon:erase(SubPid, PMon)})};
 
 handle_info(Info, State) ->
     emqx_logger:error("[Shared] Unexpected info: ~p", [Info]),
@@ -162,12 +162,8 @@ code_change(_OldVsn, State, _Extra) ->
 
 cleanup_down(SubPid) ->
     Pat = #shared_subscription{_ = '_', subpid = SubPid},
-    lists:foreach(fun(Record) ->
-                      mnesia:delete_object(?TAB, Record)
-                  end, mnesia:match_object(Pat)).
+    lists:foreach(fun(Record) -> mnesia:delete_object(?TAB, Record) end, mnesia:match_object(Pat)).
 
 update_stats(State) ->
-    emqx_stats:setstat('subscriptions/shared/count',
-                       'subscriptions/shared/max',
-                       ets:info(?TAB, size)), State.
+    emqx_stats:setstat('subscriptions/shared/count', 'subscriptions/shared/max', ets:info(?TAB, size)), State.
 
diff --git a/src/emqx_sm.erl b/src/emqx_sm.erl
index e2e5ca20c..50ce9cb75 100644
--- a/src/emqx_sm.erl
+++ b/src/emqx_sm.erl
@@ -216,26 +216,22 @@ handle_call(Req, _From, State) ->
     emqx_logger:error("[SM] Unexpected request: ~p", [Req]),
     {reply, ignore, State}.
 
-handle_cast({notify, {registered, ClientId, SessionPid}},
-            State = #state{session_pmon = PMon}) ->
-    {noreply, State#state{session_pmon = PMon:monitor(SessionPid, ClientId)}};
+handle_cast({notify, {registered, ClientId, SessionPid}}, State = #state{session_pmon = PMon}) ->
+    {noreply, State#state{session_pmon = emqx_pmon:monitor(SessionPid, ClientId, PMon)}};
 
-handle_cast({notify, {unregistered, _ClientId, SessionPid}},
-            State = #state{session_pmon = PMon}) ->
-    {noreply, State#state{session_pmon = PMon:demonitor(SessionPid)}};
+handle_cast({notify, {unregistered, _ClientId, SessionPid}}, State = #state{session_pmon = PMon}) ->
+    {noreply, State#state{session_pmon = emqx_pmon:demonitor(SessionPid, PMon)}};
 
 handle_cast(Msg, State) ->
     emqx_logger:error("[SM] Unexpected msg: ~p", [Msg]),
     {noreply, State}.
 
-handle_info({'DOWN', _MRef, process, DownPid, _Reason},
-            State = #state{session_pmon = PMon}) ->
-    case PMon:find(DownPid) of
-        undefined ->
-            {noreply, State};
-        ClientId ->
+handle_info({'DOWN', _MRef, process, DownPid, _Reason}, State = #state{session_pmon = PMon}) ->
+    case emqx_pmon:find(DownPid, PMon) of
+        undefined -> {noreply, State};
+        ClientId  ->
             unregister_session({ClientId, DownPid}),
-            {noreply, State#state{session_pmon = PMon:erase(DownPid)}}
+            {noreply, State#state{session_pmon = emqx_pmon:erase(DownPid, PMon)}}
     end;
 
 handle_info(Info, State) ->