Merge branch 'bmk/snmp/agent/20201201/serialize_notifications/OTP-17022' into maint-22

* bmk/snmp/agent/20201201/serialize_notifications/OTP-17022:
  [snmp|agent|doc] Add text about the new (extended) multi-threaded option
  [snmp|agent|test] Add test cases for extended multi-threaded agent
  [snmp|agent] Introduce notification specific worker

6 files changed, 224 insertions, 103 deletions

diff --git a/lib/snmp/doc/src/snmp_app.xml b/lib/snmp/doc/src/snmp_app.xml
index b080301143..b4c1392b71 100644
--- a/lib/snmp/doc/src/snmp_app.xml
+++ b/lib/snmp/doc/src/snmp_app.xml
@@ -188,22 +188,46 @@ in the snmp_config file!
       <tag><marker id="agent_orig_disco_opts"></marker>
         <c><![CDATA[agent_originating_discovery_opts() = [agent_originating_discovery_opt()] <optional>]]></c></tag>
       <item>
-        <p><c>agent_originating_discovery_opt() = 
-          {enable, boolean()}</c></p>
-        <p>These are options effecting discovery <c>originating</c> in this
-          agent. </p>
-        <p>The default values for the <c>originating</c> 
-          discovery options are: </p>
-        <list type="bulleted">
-          <item>enable: <c>true</c></item>
+	<p><c>agent_originating_discovery_opt() = {enable, boolean()}</c></p>
+	<p>These are options effecting discovery <c>originating</c> in this
+	agent. </p>
+	<p>The default values for the <c>originating</c>
+	discovery options are: </p>
+	<list type="bulleted">
+	  <item>enable: <c>true</c></item>
         </list>
       </item>
 
       <tag><marker id="agent_mt"></marker>
-        <c><![CDATA[multi_threaded() = bool() <optional>]]></c></tag>
+        <c><![CDATA[multi_threaded() = bool() | extended <optional>]]></c></tag>
       <item>
-        <p>If <c>true</c>, the agent is multi-threaded, with one
-          thread for each get request. </p>
+	<p>If <c>true</c> (or <c>extended</c>), the agent is multi-threaded,
+	with one thread for each get request.</p>
+	<p>The value <c>extended</c> means that a special 'process'
+	is also created intended to handle <em>all</em> notifications. </p>
+        <list>
+	  <item>
+	    <p><c>true</c> - One worker dedicated to 'set-requests' and one
+	    (main) worker for all other requests ('get-request' and
+	    notifications).</p>
+	    <p>If the 'main' worker is busy, a temporary process is
+	    spawned to handle that job ('get-request' or notification). </p>
+	  </item>
+	  <item>
+	    <p><c>extended</c> - One worker dedicated to 'set-requests',
+	    one worker dedicated to notifications and one
+	    (main) worker for all 'get-requests'. </p>
+	    <p>If the 'main' worker is busy, a temporary process is
+	    spawned to handle that 'get-request'. </p>
+	  </item>
+	</list>
+	<note>
+	  <p>Even with multi-threaded set to <c>extended</c>
+	  there is still a risk for 'reorder' when sending inform-requsts,
+	  which require a response (and may therefor require resending). </p>
+	  <p>Also, there is of  course no way to guarantee order once the
+	  package is on the network. </p>
+	</note>
         <p>Default is <c>false</c>.</p>
       </item>
 
diff --git a/lib/snmp/doc/src/snmp_config.xml b/lib/snmp/doc/src/snmp_config.xml
index 8ced577a8a..ea8973f4f8 100644
--- a/lib/snmp/doc/src/snmp_config.xml
+++ b/lib/snmp/doc/src/snmp_config.xml
@@ -184,10 +184,35 @@
       </item>
 
       <tag><marker id="agent_mt"></marker>
-        <c><![CDATA[multi_threaded() = bool() <optional>]]></c></tag>
+        <c><![CDATA[multi_threaded() = bool() | extended<optional>]]></c></tag>
       <item>
-        <p>If <c>true</c>, the agent is multi-threaded, with one
-          thread for each get request. </p>
+	<p>If <c>true</c> (or <c>extended</c>), the agent is multi-threaded,
+	with one thread for each get request. </p>
+	<p>The value <c>extended</c> means that a special 'process'
+	is also created intended to handle <em>all</em> notifications. </p>
+        <list>
+	  <item>
+	    <p><c>true</c> - One worker dedicated to 'set-requests' and one
+	    (main) worker for all other requests ('get-request' and
+	    notifications).</p>
+	    <p>If the 'main' worker is busy, a temporary process is
+	    spawned to handle that job ('get-request' or notification). </p>
+	  </item>
+	  <item>
+	    <p><c>extended</c> - One worker dedicated to 'set-requests',
+	    one worker dedicated to notifications and one
+	    (main) worker for all 'get-requests'. </p>
+	    <p>If the 'main' worker is busy, a temporary process is
+	    spawned to handle that 'get-request'. </p>
+	  </item>
+        </list>
+	<note>
+	  <p>Even with multi-threaded set to <c>extended</c>
+	  there is still a risk for 'reorder' when sending inform-requsts,
+	  which require a response (and may therefor require resending). </p>
+	  <p>Also, there is of  course no way to guarantee order once the
+	  package is on the network. </p>
+	</note>
         <p>Default is <c>false</c>.</p>
       </item>
 
diff --git a/lib/snmp/src/agent/snmpa_agent.erl b/lib/snmp/src/agent/snmpa_agent.erl
index cc3bef15af..649a54b844 100644
--- a/lib/snmp/src/agent/snmpa_agent.erl
+++ b/lib/snmp/src/agent/snmpa_agent.erl
@@ -63,7 +63,7 @@
 -export([get_request_limit/1, set_request_limit/2]).
 -export([invalidate_ca_cache/0]).
 -export([increment_counter/3]).
--export([restart_worker/1, restart_set_worker/1]).
+-export([restart_worker/1, restart_set_worker/1, restart_notif_worker/1]).
 
 %% For backward compatibillity
 -export([send_trap/6, send_trap/7]).
@@ -71,7 +71,7 @@
 %% Internal exports
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
 	 terminate/2, code_change/3, tr_var/2, tr_varbind/1,
-	 handle_pdu/8, worker/2, worker_loop/1, 
+	 handle_pdu/8, worker/4, worker_loop/2, 
 	 do_send_trap/7, do_send_trap/8]).
 %% <BACKWARD-COMPAT>
 -export([handle_pdu/7, 
@@ -177,6 +177,7 @@
 		worker, 
 		worker_state = ready,
 		set_worker, 
+		notif_worker, 
 		multi_threaded, 
 		ref, 
 		vsns,
@@ -249,6 +250,9 @@ restart_worker(Agent) ->
 restart_set_worker(Agent) ->
     call(Agent, restart_set_worker).
 
+restart_notif_worker(Agent) ->
+    call(Agent, restart_notif_worker).
+
 get_log_type(Agent) ->
     call(Agent, get_log_type).
 
@@ -391,11 +395,12 @@ do_init(Prio, Parent, Ref, Options) ->
     put(net_if, NetIfPid),
     put(mibserver, MibPid),
     process_flag(trap_exit, true),
-    {Worker, SetWorker} = workers_start(MultiT),
+    {Worker, SetWorker, NotifWorker} = workers_start(MultiT),
     {ok, #state{type           = Type, 
 		parent         = Parent, 
 		worker         = Worker,
 		set_worker     = SetWorker,
+		notif_worker   = NotifWorker,
 		multi_threaded = MultiT, 
 		ref            = Ref,
 		vsns           = Vsns,
@@ -975,9 +980,13 @@ handle_info({'EXIT', Pid, Reason}, #state{worker = Pid} = S) ->
     NewWorker = worker_start(), 
     {noreply, S#state{worker = NewWorker}};
 handle_info({'EXIT', Pid, Reason}, #state{set_worker = Pid} = S) ->
-    ?vlog("set-worker (~p) exited -> create new ~n   ~p", [Pid,Reason]),
+    ?vlog("set-worker (~p) exited -> create new ~n   ~p", [Pid, Reason]),
     NewWorker = set_worker_start(), 
     {noreply, S#state{set_worker = NewWorker}};
+handle_info({'EXIT', Pid, Reason}, #state{notif_worker = Pid} = S) ->
+    ?vlog("notif-worker (~p) exited -> create new ~n   ~p", [Pid, Reason]),
+    NewWorker = notif_worker_start(), 
+    {noreply, S#state{notif_worker = NewWorker}};
 handle_info({'EXIT', Pid, Reason}, #state{parent = Pid} = S) ->
     ?vlog("parent (~p) exited for reason ~n~p", [Pid,Reason]),
     {stop, {parent_died, Reason}, S};
@@ -1415,13 +1424,17 @@ handle_cast({verbosity, Verbosity}, S) ->
     ?vlog("verbosity: ~p -> ~p",[get(verbosity), Verbosity]),
     put(verbosity,snmp_verbosity:validate(Verbosity)),
     case S#state.worker of
-	Pid when is_pid(Pid) -> Pid ! ?mk_verbosity_wreq(Verbosity);
+	Pid1 when is_pid(Pid1) -> Pid1 ! ?mk_verbosity_wreq(Verbosity);
 	_ -> ok
     end,
     case S#state.set_worker of
 	Pid2 when is_pid(Pid2) -> Pid2 ! ?mk_verbosity_wreq(Verbosity);
 	_ -> ok
     end,
+    case S#state.notif_worker of
+	Pid3 when is_pid(Pid3) -> Pid3 ! ?mk_verbosity_wreq(Verbosity);
+	_ -> ok
+    end,
     {noreply, S};
     
 handle_cast({sub_agents_verbosity,Verbosity}, S) ->
@@ -1447,14 +1460,16 @@ handle_cast(Msg, S) ->
     {noreply, S}.
 
     
-terminate(shutdown, #state{worker     = Worker,
-			   set_worker = SetWorker,
-			   backup     = Backup, 
+terminate(shutdown, #state{worker       = Worker,
+			   set_worker   = SetWorker,
+			   notif_worker = NotifWorker,
+			   backup       = Backup, 
 			   ref = Ref}) ->
     %% Ordered shutdown - stop misc-workers, net_if, mib-server and note-store.
     backup_server_stop(Backup), 
     worker_stop(Worker, 100),
     worker_stop(SetWorker, 100),
+    worker_stop(NotifWorker, 100),
     snmpa_misc_sup:stop_net_if(Ref), 
     snmpa_misc_sup:stop_mib_server(Ref);
 terminate(_Reason, _S) ->
@@ -1600,20 +1615,26 @@ backup_server_stop(_) ->
     ok.
 
 
+workers_start(extended) ->
+    ?vdebug("start worker, set-worker and notif-worker", []),
+    {worker_start(), set_worker_start(), notif_worker_start()};
 workers_start(true) ->
-    ?vdebug("start worker and set-worker",[]),
-    {worker_start(), set_worker_start()};
+    ?vdebug("start worker and set-worker", []),
+    {worker_start(), set_worker_start(), undefined};
 workers_start(_) ->
-    {undefined, undefined}.
+    {undefined, undefined, undefined}.
 
 worker_start() ->
-    worker_start(get()).
+    worker_start(mw, true, get()).
 
 set_worker_start() ->
-    worker_start([{master, self()} | get()]).
+    worker_start(sw, false, [{master, self()} | get()]).
+
+notif_worker_start() ->
+    worker_start(nw, false, [{master, self()} | get()]).
 
-worker_start(Dict) ->
-    proc_lib:spawn_link(?MODULE, worker, [self(), Dict]).
+worker_start(SName, Report, Dict) ->
+    proc_lib:spawn_link(?MODULE, worker, [self(), SName, Report, Dict]).
 
 %% worker_stop(Pid) ->
 %%     worker_stop(Pid, infinity).
@@ -1783,13 +1804,13 @@ do_send_trap(TrapRec, NotifyName, ContextName, Recv, Vbs,
     snmpa_trap:send_trap(TrapRec, NotifyName, ContextName, Recv, Vbs, 
 			 LocalEngineID, ExtraInfo, get(net_if)).
 
-worker(Master, Dict) ->
+worker(Master, SName, Report, Dict) ->
     lists:foreach(fun({Key, Val}) -> put(Key, Val) end, Dict),
-    put(sname, worker_short_name(get(sname))),
+    put(sname, worker_short_name(get(sname), SName)),
     ?vlog("starting",[]),
-    worker_loop(Master).
+    worker_loop(Master, Report).
 
-worker_loop(Master) ->
+worker_loop(Master, Report) ->
     Res = 
 	receive
 	    #wrequest{cmd  = handle_pdu, 
@@ -1813,7 +1834,7 @@ worker_loop(Master) ->
 			C:E:S ->
 			    exit({worker_crash, Req, C, E, S})
 		    end,
-		Master ! worker_available,
+                worker_maybe_announce_available(Master, Report),
 		HandlePduRes; % For debugging...
 	    
 	    
@@ -1840,7 +1861,7 @@ worker_loop(Master) ->
 			C:E:S ->
 			    exit({worker_crash, Req, C, E, S})
 		    end,
-		Master ! worker_available, 
+                worker_maybe_announce_available(Master, Report),
 		SendTrapRes; % For debugging...
 	    
 	    
@@ -1853,8 +1874,10 @@ worker_loop(Master) ->
 	    #wrequest{cmd  = terminate} ->
 		?vtrace("worker_loop -> received terminate request", []),
 		exit(normal);
-	    
-	    
+
+
+
+
 	    %% *************************************************************
 	    %% 
 	    %%         Kept for backward compatibillity reasons
@@ -1904,7 +1927,12 @@ worker_loop(Master) ->
 	end,
     ?vtrace("worker_loop -> wrap with"
 	    "~n   ~p", [Res]),
-    ?MODULE:worker_loop(Master).
+    ?MODULE:worker_loop(Master, Report).
+
+worker_maybe_announce_available(Master, true) ->
+    Master ! worker_available;
+worker_maybe_announce_available(_Master, _Report) ->
+    ok.
 
 
 %%-----------------------------------------------------------------
@@ -2186,6 +2214,13 @@ do_handle_send_trap(S, TrapRec, NotifyName, ContextName, Recv, Varbinds,
 				 Recv, Vbs, LocalEngineID, ExtraInfo, 
 				 get(net_if)),
 	    {ok, S};
+	master_agent when (S#state.multi_threaded =:= extended) ->
+	    %% Send to main worker
+	    ?vtrace("do_handle_send_trap -> send to notif-worker",[]),
+	    S#state.notif_worker ! ?mk_send_trap_wreq(TrapRec, NotifyName, 
+                                                      ContextName, Recv, Vbs,
+                                                      LocalEngineID, ExtraInfo),
+	    {ok, S};
 	master_agent when S#state.worker_state =:= busy ->
 	    %% Main worker busy => create new worker
 	    ?vtrace("do_handle_send_trap -> main worker busy: "
@@ -2195,7 +2230,7 @@ do_handle_send_trap(S, TrapRec, NotifyName, ContextName, Recv, Varbinds,
 	    {ok, S};
 	master_agent ->
 	    %% Send to main worker
-	    ?vtrace("do_handle_send_trap -> send to main worker",[]),
+	    ?vtrace("do_handle_send_trap -> send to main worker", []),
 	    S#state.worker ! ?mk_send_trap_wreq(TrapRec, NotifyName, 
 						ContextName, Recv, Vbs,
 						LocalEngineID, ExtraInfo),
@@ -3225,8 +3260,10 @@ mapfoldl(_F, _Eas, Accu, []) -> {Accu,[]}.
 short_name(none) -> ma;
 short_name(_Pid) -> sa.
 
-worker_short_name(ma) -> maw;
-worker_short_name(_)  -> saw.
+worker_short_name(ma, mw) -> mamw;
+worker_short_name(ma, sw) -> masw;
+worker_short_name(ma, nw) -> manw;
+worker_short_name(_,  _)  -> saw.
 
 trap_sender_short_name(ma) -> mats;
 trap_sender_short_name(_)  -> sats.
@@ -3318,27 +3355,33 @@ handle_set_request_limit(_, _) ->
     {error, not_supported}.
 
 
-agent_info(#state{worker = W, set_worker = SW}) -> 
-    case (catch get_agent_info(W, SW)) of
+agent_info(#state{worker = W, set_worker = SW, notif_worker = NW}) -> 
+    case (catch get_agent_info(W, SW, NW)) of
 	Info when is_list(Info) ->
 	    Info;
 	E ->
 	    [{error, E}]
     end.
 
-get_agent_info(W, SW) ->
+get_agent_info(W, SW, NW) ->
     MASz   = proc_mem(self()),
-    WSz    = proc_mem(W),
-    SWSz   = proc_mem(SW),
     ATSz   = tab_mem(snmp_agent_table),
     CCSz   = tab_mem(snmp_community_cache),
     VacmSz = tab_mem(snmpa_vacm),
-    [{process_memory, [{master_agent, MASz}, 
-		       {worker,       WSz}, 
-		       {set_worker,   SWSz}]}, 
-     {db_memory, [{agent,           ATSz}, 
-		  {community_cache, CCSz}, 
-		  {vacm,            VacmSz}]}].
+    [{process_memory,
+      [{master_agent, MASz}] ++
+          process_memory(worker,       W) ++
+          process_memory(set_worker,   SW) ++
+          process_memory(notif_worker, NW)},
+     {db_memory,
+      [{agent,           ATSz},
+       {community_cache, CCSz},
+       {vacm,            VacmSz}]}].
+
+process_memory(Tag, P) when is_pid(P) ->
+    [{Tag, proc_mem(P)}];
+process_memory(_, _) ->
+    [].
 
 proc_mem(P) when is_pid(P) ->
     case (catch erlang:process_info(P, memory)) of
diff --git a/lib/snmp/src/misc/snmp_verbosity.erl b/lib/snmp/src/misc/snmp_verbosity.erl
index 9bc3e2762f..0572ebea03 100644
--- a/lib/snmp/src/misc/snmp_verbosity.erl
+++ b/lib/snmp/src/misc/snmp_verbosity.erl
@@ -100,7 +100,9 @@ image_of_verbosity(_)     -> "".
 
 %% ShortName
 image_of_sname(ma)        -> "MASTER-AGENT";
-image_of_sname(maw)       -> io_lib:format("MASTER-AGENT-worker(~p)",[self()]);
+image_of_sname(mamw)      -> io_lib:format("MASTER-AGENT-main_worker(~p)",[self()]);
+image_of_sname(masw)      -> io_lib:format("MASTER-AGENT-set_worker(~p)",[self()]);
+image_of_sname(manw)      -> io_lib:format("MASTER-AGENT-notif_worker(~p)",[self()]);
 image_of_sname(madis)     -> io_lib:format("MASTER-AGENT-discovery_inform_sender(~p)",
 					   [self()]);
 image_of_sname(mais)      -> io_lib:format("MASTER-AGENT-inform_sender(~p)",
diff --git a/lib/snmp/test/snmp_agent_SUITE.erl b/lib/snmp/test/snmp_agent_SUITE.erl
index 2a6cfbedbe..d433692b0a 100644
--- a/lib/snmp/test/snmp_agent_SUITE.erl
+++ b/lib/snmp/test/snmp_agent_SUITE.erl
@@ -204,7 +204,7 @@
 	 v3_sha_auth/1,
 	 v3_des_priv/1, 
 
-	 %% all_tcs - test_multi_threaded
+	 %% all_tcs - test_multi_threaded, test_multi_threaded_ext
 	 multi_threaded/1, 
 	 mt_trap/1, 
 	 
@@ -319,7 +319,7 @@
 	 db_notify_client_test/0, 
 	 notify/2, 
 	 multi_threaded_test/0, 
-	 mt_trap_test/1, 
+	 mt_trap_test/2, 
 	 types_v2_test/0, 
 	 implied_test/1, 
 	 sparse_table_test/0, 
@@ -535,6 +535,7 @@ groups() ->
      {test_v3,                       [], v3_cases()},
      {test_v3_ipv6,                  [], v3_cases_ipv6()},
      {test_multi_threaded,           [], mt_cases()},
+     {test_multi_threaded_ext,       [], mt_cases()},
      {multiple_reqs,                 [], mul_cases()},
      {multiple_reqs_2,               [], mul_cases_2()},
      {multiple_reqs_3,               [], mul_cases_3()},
@@ -568,6 +569,7 @@ all_cases() ->
      {group, test_v1_v2_ipv6},
      {group, test_v3_ipv6},
      {group, test_multi_threaded}, 
+     {group, test_multi_threaded_ext}, 
      {group, mib_storage},
      {group, tickets1}
     ].
@@ -654,7 +656,9 @@ init_per_group(multiple_reqs_2 = GroupName, Config) ->
 init_per_group(multiple_reqs_3 = GroupName, Config) -> 
     init_mul(snmp_test_lib:init_group_top_dir(GroupName, Config));
 init_per_group(test_multi_threaded = GroupName, Config) -> 
-    init_mt(snmp_test_lib:init_group_top_dir(GroupName, Config));
+    init_mt(snmp_test_lib:init_group_top_dir(GroupName, Config), true);
+init_per_group(test_multi_threaded_ext = GroupName, Config) -> 
+    init_mt(snmp_test_lib:init_group_top_dir(GroupName, Config), extended);
 init_per_group(test_v3 = GroupName, Config) -> 
     case snmp_test_lib:crypto_start() of
         ok ->
@@ -764,49 +768,51 @@ end_per_group(v2_inform, Config) ->
 end_per_group(v3_inform, Config) -> 
     finish_v3_inform(Config);
 end_per_group(multiple_reqs, Config) -> 
-	finish_mul(Config);
+    finish_mul(Config);
 end_per_group(multiple_reqs_2, Config) -> 
     finish_mul(Config);
 end_per_group(multiple_reqs_3, Config) -> 
     finish_mul(Config);
 end_per_group(test_multi_threaded, Config) -> 
-	finish_mt(Config);
+    finish_mt(Config);
+end_per_group(test_multi_threaded_ext, Config) -> 
+    finish_mt(Config);
 end_per_group(test_v3_ipv6, Config) ->
-	finish_v3(Config);
+    finish_v3(Config);
 end_per_group(test_v1_v2_ipv6, Config) ->
-	finish_v1_v2(Config);
+    finish_v1_v2(Config);
 end_per_group(test_v2_ipv6, Config) ->
-	finish_v2(Config);
+    finish_v2(Config);
 end_per_group(test_v1_ipv6, Config) ->
-	finish_v1(Config);
+    finish_v1(Config);
 end_per_group(test_v3, Config) ->
-	finish_v3(Config);
+    finish_v3(Config);
 end_per_group(test_v1_v2, Config) ->
-	finish_v1_v2(Config);
+    finish_v1_v2(Config);
 end_per_group(test_v2, Config) ->
-	finish_v2(Config);
+    finish_v2(Config);
 end_per_group(test_v1, Config) ->
-	finish_v1(Config);
+    finish_v1(Config);
 end_per_group(misc, Config) ->
-	finish_misc(Config);
+    finish_misc(Config);
 end_per_group(mib_storage_varm_mnesia, Config) ->
-	finish_varm_mib_storage_mnesia(Config);
+    finish_varm_mib_storage_mnesia(Config);
 end_per_group(mib_storage_varm_dets, Config) ->
-	finish_varm_mib_storage_dets(Config);
+    finish_varm_mib_storage_dets(Config);
 end_per_group(mib_storage_size_check_mnesia, Config) ->
-	finish_size_check_msm(Config);
+    finish_size_check_msm(Config);
 end_per_group(mib_storage_size_check_dets, Config) ->
-	finish_size_check_msd(Config);
+    finish_size_check_msd(Config);
 end_per_group(mib_storage_size_check_ets, Config) ->
-	finish_size_check_mse(Config);
+    finish_size_check_mse(Config);
 end_per_group(mib_storage_mnesia, Config) ->
-	finish_mib_storage_mnesia(Config);
+    finish_mib_storage_mnesia(Config);
 end_per_group(mib_storage_dets, Config) ->
-	finish_mib_storage_dets(Config);
+    finish_mib_storage_dets(Config);
 end_per_group(mib_storage_ets, Config) ->
-	finish_mib_storage_ets(Config);
+    finish_mib_storage_ets(Config);
 end_per_group(_GroupName, Config) ->
-	Config.
+    Config.
 
 
 
@@ -1040,8 +1046,8 @@ start_v3_agent(Config, Opts) ->
 start_bilingual_agent(Config) ->
     ?ALIB:start_bilingual_agent(Config).
 
-start_multi_threaded_agent(Config) when is_list(Config) ->
-    ?ALIB:start_mt_agent(Config).
+start_multi_threaded_agent(Config, MT) when is_list(Config) ->
+    [{multi_threaded, MT} | ?ALIB:start_mt_agent(Config, MT)].
 
 stop_agent(Config) ->
     ?ALIB:stop_agent(Config).
@@ -2117,7 +2123,7 @@ mt_cases() ->
      mt_trap
     ].
 
-init_mt(Config) when is_list(Config) ->
+init_mt(Config, MT) when is_list(Config) ->
     SaNode = ?config(snmp_sa, Config),
     create_tables(SaNode),
     AgentConfDir = ?config(agent_conf_dir, Config),
@@ -2125,7 +2131,7 @@ init_mt(Config) when is_list(Config) ->
     Ip       = ?config(ip, Config),
     ?line ok = config([v2], MgrDir, AgentConfDir, 
 		      tuple_to_list(Ip), tuple_to_list(Ip)),
-    [{vsn, v2} | start_multi_threaded_agent(Config)].
+    [{vsn, v2} | start_multi_threaded_agent(Config, MT)].
 
 finish_mt(Config) when is_list(Config) ->
     delete_tables(),
@@ -2290,10 +2296,11 @@ mt_trap(Config) when is_list(Config) ->
     ?P(mt_trap), 
     init_case(Config),
     MA = whereis(snmp_master_agent),
+    MT = ?config(multi_threaded, Config),
     
     ?line load_master("Test1"),
     ?line load_master("TestTrapv2"),
-    try_test(mt_trap_test, [MA]),
+    try_test(mt_trap_test, [MA, MT]),
     ?line unload_master("TestTrapv2"),
     ?line unload_master("Test1"),
     ok.
@@ -3959,37 +3966,51 @@ multi_threaded_test() ->
     ?line ?expect1([{[sysLocation,0], "kalle"}]).
 
 %% Req. Test1, TestTrapv2
-mt_trap_test(MA) ->
-    ?NPRINT("Testing trap-sending with multi threaded agent..."),
-    ?DBG("mt_trap_test(01) -> issue testTrapv22 (standard trap)", []),
+mt_trap_test(MA, MT) ->
+    ?NPRINT("Testing trap-sending with multi threaded (~w) agent...", [MT]),
+    ?IPRINT("mt_trap_test(01) -> issue testTrapv22 (standard trap)", []),
     snmpa:send_trap(MA, testTrapv22, "standard trap"),
-    ?DBG("mt_trap_test(02) -> await v2trap", []),
+    ?IPRINT("mt_trap_test(02) -> await v2trap", []),
     ?line ?expect2(v2trap, [{[sysUpTime, 0],   any},
 			    {[snmpTrapOID, 0], ?system ++ [0,1]}]),
 
-    ?DBG("mt_trap_test(03) -> issue mtTrap (standard trap)", []),
+    %% multi-threaded = true
+    %% This will *lock* the 'main thread' of a multi-threaded agent,
+    %% the worker state will be 'busy'. Therefor when a new request
+    %% arrives a new *temporary* worker will be spawned.
+    ?IPRINT("mt_trap_test(03) -> issue mtTrap (standard trap)", []),
     snmpa:send_trap(MA, mtTrap, "standard trap"),
     Pid = get_multi_pid(),
-    ?DBG("mt_trap_test(04) -> multi pid: ~p. Now request sysUpTime...", [Pid]),
+    ?IPRINT("mt_trap_test(04) -> multi pid: ~p. Now request sysUpTime...", [Pid]),
     g([[sysUpTime,0]]),
 
-    ?DBG("mt_trap_test(06) -> await sysUpTime", []),
+    ?IPRINT("mt_trap_test(06) -> await sysUpTime", []),
     ?line ?expect1([{[sysUpTime,0], any}]),
-    ?DBG("mt_trap_test(07) -> issue testTrapv22 (standard trap)", []),
-    snmpa:send_trap(MA, testTrapv22, "standard trap"),
-    ?DBG("mt_trap_test(08) -> await v2trap", []),
-    ?line ?expect2(v2trap, 
-		   [{[sysUpTime, 0],   any}, 
-		    {[snmpTrapOID, 0], ?system ++ [0,1]}]),
 
-    ?DBG("mt_trap_test(09) -> send continue to multi-pid", []),
+    %% This will *only* work if multi-threaded is 'true', not 'extended'
+    %% since in the latter case all notifications are serialized through
+    %% a dedicated worker, which is now locked (see above).
+
+    if
+        (MT =:= true) ->
+            ?IPRINT("mt_trap_test(07) -> issue testTrapv22 (standard trap)", []),
+            snmpa:send_trap(MA, testTrapv22, "standard trap"),
+            ?IPRINT("mt_trap_test(08) -> await v2trap", []),
+            ?line ?expect2(v2trap, 
+                           [{[sysUpTime, 0],   any}, 
+                            {[snmpTrapOID, 0], ?system ++ [0,1]}]);
+        true ->
+            ok
+    end,
+
+    ?IPRINT("mt_trap_test(09) -> send continue to multi-pid", []),
     Pid ! continue,
 
-    ?DBG("mt_trap_test(10) -> await v2trap", []),
+    ?IPRINT("mt_trap_test(10) -> await v2trap", []),
     ?line ?expect2(v2trap, [{[sysUpTime, 0], any},
 			    {[snmpTrapOID, 0], ?testTrap ++ [2]},
 			    {[multiStr,0], "ok"}]),
-    ?DBG("mt_trap_test(11) -> done", []),
+    ?IPRINT("mt_trap_test(11) -> done", []),
     ok.
 
     
diff --git a/lib/snmp/test/snmp_agent_test_lib.erl b/lib/snmp/test/snmp_agent_test_lib.erl
index 6a4c582f36..b3c492e4ce 100644
--- a/lib/snmp/test/snmp_agent_test_lib.erl
+++ b/lib/snmp/test/snmp_agent_test_lib.erl
@@ -26,7 +26,7 @@
 	 start_v2_agent/1,        start_v2_agent/2, 
 	 start_v3_agent/1,        start_v3_agent/2, 
 	 start_bilingual_agent/1, start_bilingual_agent/2, 
-	 start_mt_agent/1,        start_mt_agent/2, 
+	 start_mt_agent/1,        start_mt_agent/2,         start_mt_agent/3, 
 	 stop_agent/1,
 
 	 %% start_sup/0,      stop_sup/2,
@@ -560,12 +560,18 @@ start_bilingual_agent(Config, Opts)
   when is_list(Config) andalso is_list(Opts) ->
     start_agent(Config, [v1,v2], Opts).
  
-start_mt_agent(Config) when is_list(Config) ->
-    start_agent(Config, [v2], [{multi_threaded, true}]).
- 
-start_mt_agent(Config, Opts) when is_list(Config) andalso is_list(Opts) ->
-    start_agent(Config, [v2], [{multi_threaded, true}|Opts]).
+start_mt_agent(Config) ->
+    start_mt_agent(Config, true, []).
  
+start_mt_agent(Config, MT) ->
+    start_mt_agent(Config, MT, []).
+
+start_mt_agent(Config, MT, Opts)
+  when is_list(Config) andalso 
+       ((MT =:= true) orelse (MT =:= extended)) andalso 
+       is_list(Opts) ->
+    start_agent(Config, [v2], [{multi_threaded, MT} | Opts]).
+
 start_agent(Config, Vsns) ->
     start_agent(Config, Vsns, []).
 start_agent(Config, Vsns, Opts) ->