4 files changed, 28 insertions, 5 deletions

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 62191c4abf..cd6fbf276b 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -3202,6 +3202,11 @@ int enif_demonitor_process(ErlNifEnv* env, void* obj, const ErlNifMonitor* monit
     return 0;
 }
 
+int enif_compare_monitors(const ErlNifMonitor *monitor1,
+                          const ErlNifMonitor *monitor2)
+{
+    return memcmp(monitor1,monitor2,sizeof(ErlNifMonitor));
+}
 
 /***************************************************************************
  **                              load_nif/2                               **
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 1fc6842acc..01d9e386ed 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -179,6 +179,7 @@ ERL_NIF_API_FUNC_DECL(int,enif_select,(ErlNifEnv* env, ErlNifEvent e, enum ErlNi
 ERL_NIF_API_FUNC_DECL(ErlNifResourceType*,enif_open_resource_type_x,(ErlNifEnv*, const char* name_str, const ErlNifResourceTypeInit*, ErlNifResourceFlags flags, ErlNifResourceFlags* tried));
 ERL_NIF_API_FUNC_DECL(int, enif_monitor_process,(ErlNifEnv*,void* obj,const ErlNifPid*,ErlDrvMonitor *monitor));
 ERL_NIF_API_FUNC_DECL(int, enif_demonitor_process,(ErlNifEnv*,void* obj,const ErlDrvMonitor *monitor));
+ERL_NIF_API_FUNC_DECL(int, enif_compare_monitors,(const ErlNifMonitor*,const ErlNifMonitor*));
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
@@ -340,6 +341,7 @@ ERL_NIF_API_FUNC_DECL(int, enif_demonitor_process,(ErlNifEnv*,void* obj,const Er
 #  define enif_open_resource_type_x ERL_NIF_API_FUNC_MACRO(enif_open_resource_type_x)
 #  define enif_monitor_process ERL_NIF_API_FUNC_MACRO(enif_monitor_process)
 #  define enif_demonitor_process ERL_NIF_API_FUNC_MACRO(enif_demonitor_process)
+#  define enif_compare_monitors ERL_NIF_API_FUNC_MACRO(enif_compare_monitors)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index d88ac01e46..9932b526b9 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -598,10 +598,11 @@ monitor_process_a(Config) ->
                                     end
                             end),
                 R_ptr = alloc_monitor_resource_nif(),
-                {0, Mon} = monitor_process_nif(R_ptr, Pid, UseMsgEnv, self()),
+                {0, Mon1} = monitor_process_nif(R_ptr, Pid, UseMsgEnv, self()),
                 [R_ptr] = monitored_by(Pid),
                 Terminator(Pid),
-                [{monitor_resource_down, R_ptr, Pid, Mon}] = flush(),
+                [{monitor_resource_down, R_ptr, Pid, Mon2}] = flush(),
+                0 = compare_monitors_nif(Mon1, Mon2),
                 [] = last_resource_dtor_call(),
                 ok = release_resource(R_ptr),
                 {R_ptr, _, 1} = last_resource_dtor_call()
@@ -650,8 +651,9 @@ monitor_process_c(Config) ->
                              Papa ! {self(), done, R_ptr, Mon},
                              exit
                      end),
-    [{Pid, done, R_ptr, Mon},
-     {monitor_resource_down, R_ptr, Pid, Mon}] = flush(),
+    [{Pid, done, R_ptr, Mon1},
+     {monitor_resource_down, R_ptr, Pid, Mon2}] = flush(),
+    compare_monitors_nif(Mon1, Mon2),
     {R_ptr, _, 1} = last_resource_dtor_call(),
     ok.
 
@@ -2657,6 +2659,7 @@ last_fd_stop_call() -> ?nif_stub.
 alloc_monitor_resource_nif() -> ?nif_stub.
 monitor_process_nif(_,_,_,_) -> ?nif_stub.
 demonitor_process_nif(_,_) -> ?nif_stub.
+compare_monitors_nif(_,_) -> ?nif_stub.
 monitor_frenzy_nif(_,_,_,_) -> ?nif_stub.
 
 %% maps
diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
index 05b4b05e16..a9622e3b8d 100644
--- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
+++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c
@@ -2407,6 +2407,18 @@ static ERL_NIF_TERM demonitor_process_nif(ErlNifEnv* env, int argc, const ERL_NI
     return enif_make_int(env, res);
 }
 
+static ERL_NIF_TERM compare_monitors_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{
+    ErlNifMonitor m1, m2;
+    if (!get_monitor(env, argv[0], &m1)
+        || !get_monitor(env, argv[1], &m2)) {
+        return enif_make_badarg(env);
+    }
+
+    return enif_make_int(env, enif_compare_monitors(&m1, &m2));
+}
+
+
 /*********** monitor_frenzy ************/
 
 struct frenzy_rand_bits
@@ -2763,7 +2775,7 @@ static void frenzy_resource_down(ErlNifEnv* env, void* obj, ErlNifPid* pid,
     for (mix = 0; mix < FRENZY_MONITORS_MAX; mix++) {
         if (r->monv[mix].pid.pid == pid->pid && r->monv[mix].state >= MON_TRYING) {
             enif_mutex_lock(r->monv[mix].lock);
-            if (memcmp(mon, &r->monv[mix].mon, sizeof(*mon)) == 0) {
+            if (enif_compare_monitors(mon, &r->monv[mix].mon) == 0) {
                 assert(r->monv[mix].state >= MON_ACTIVE);
                 r->monv[mix].state = MON_FREE_DOWN;
                 enif_mutex_unlock(r->monv[mix].lock);
@@ -2864,6 +2876,7 @@ static ErlNifFunc nif_funcs[] =
     {"alloc_monitor_resource_nif", 0, alloc_monitor_resource_nif},
     {"monitor_process_nif", 4, monitor_process_nif},
     {"demonitor_process_nif", 2, demonitor_process_nif},
+    {"compare_monitors_nif", 2, compare_monitors_nif},
     {"monitor_frenzy_nif", 4, monitor_frenzy_nif}
 };