Allow an infinite timeout to shutdown worker processes

Now, in child specification, the shutdown value can also be set to infinity
for worker children. This restriction was removed because this is not always
possible to predict the shutdown time for a worker. This is highly
application-dependent.

4 files changed, 18 insertions, 16 deletions

diff --git a/lib/stdlib/doc/src/supervisor.xml b/lib/stdlib/doc/src/supervisor.xml
index ec607d6e4c..b4baf2f0a0 100644
--- a/lib/stdlib/doc/src/supervisor.xml
+++ b/lib/stdlib/doc/src/supervisor.xml
@@ -169,7 +169,8 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules}
           <c>exit(Child,kill)</c>.</p>
         <p>If the child process is another supervisor, <c>Shutdown</c>
           should be set to <c>infinity</c> to give the subtree ample
-          time to shutdown.</p>
+          time to shutdown. It is also allowed to set it to <c>infinity</c>,
+          if the child process is a worker.</p>
         <p><em>Important note on simple-one-for-one supervisors:</em>
           The dynamically created child processes of a
           simple-one-for-one supervisor are not explicitly killed,
diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index 9da0d52f8c..051dca462b 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -1053,7 +1053,7 @@ validRestartType(RestartType) -> throw({invalid_restart_type, RestartType}).
 
 validShutdown(Shutdown, _) 
   when is_integer(Shutdown), Shutdown > 0 -> true;
-validShutdown(infinity, supervisor)    -> true;
+validShutdown(infinity, _)             -> true;
 validShutdown(brutal_kill, _)          -> true;
 validShutdown(Shutdown, _)             -> throw({invalid_shutdown, Shutdown}).
 
diff --git a/lib/stdlib/test/supervisor_SUITE.erl b/lib/stdlib/test/supervisor_SUITE.erl
index 2aa3131aeb..9d47233422 100644
--- a/lib/stdlib/test/supervisor_SUITE.erl
+++ b/lib/stdlib/test/supervisor_SUITE.erl
@@ -209,8 +209,8 @@ sup_start_fail(Config) when is_list(Config) ->
 %%-------------------------------------------------------------------------
 
 sup_stop_infinity(doc) ->
-    ["See sup_stop/1 when Shutdown = infinity, this walue is only allowed "
-     "for children of type supervisor"];
+    ["See sup_stop/1 when Shutdown = infinity, this walue is allowed "
+     "for children of type supervisor _AND_ worker"];
 sup_stop_infinity(suite) -> [];
 
 sup_stop_infinity(Config) when is_list(Config) ->
@@ -221,12 +221,13 @@ sup_stop_infinity(Config) when is_list(Config) ->
     Child2 = {child2, {supervisor_1, start_child, []}, permanent,
 	      infinity, worker, []},
     {ok, CPid1} = supervisor:start_child(sup_test, Child1),
+    {ok, CPid2} = supervisor:start_child(sup_test, Child2),
     link(CPid1),
-    {error, {invalid_shutdown,infinity}} =
-	supervisor:start_child(sup_test, Child2),
+    link(CPid2),
 
     terminate(Pid, shutdown),
-    check_exit_reason(CPid1, shutdown).
+    check_exit_reason(CPid1, shutdown),
+    check_exit_reason(CPid2, shutdown).
 
 %%-------------------------------------------------------------------------
 
@@ -458,9 +459,8 @@ child_specs(Config) when is_list(Config) ->
     B2 = {child, {m,f,[a]}, prmanent, 1000, worker, []}, 
     B3 = {child, {m,f,[a]}, permanent, -10, worker, []},
     B4 = {child, {m,f,[a]}, permanent, 10, wrker, []},
-    B5 = {child, {m,f,[a]}, permanent, infinity, worker, []},
-    B6 = {child, {m,f,[a]}, permanent, 1000, worker, dy},
-    B7 = {child, {m,f,[a]}, permanent, 1000, worker, [1,2,3]},
+    B5 = {child, {m,f,[a]}, permanent, 1000, worker, dy},
+    B6 = {child, {m,f,[a]}, permanent, 1000, worker, [1,2,3]},
 
     %% Correct child specs!
     %% <Modules> (last parameter in a child spec) can be [] as we do 
@@ -469,6 +469,7 @@ child_specs(Config) when is_list(Config) ->
     C2 = {child, {m,f,[a]}, permanent, 1000, supervisor, []},
     C3 = {child, {m,f,[a]}, temporary, 1000, worker, dynamic},
     C4 = {child, {m,f,[a]}, transient, 1000, worker, [m]},
+    C5 = {child, {m,f,[a]}, permanent, infinity, worker, [m]},
 
     {error, {invalid_mfa,mfa}} = supervisor:start_child(sup_test, B1),
     {error, {invalid_restart_type, prmanent}} =
@@ -477,9 +478,8 @@ child_specs(Config) when is_list(Config) ->
 	= supervisor:start_child(sup_test, B3),
     {error, {invalid_child_type,wrker}}
 	= supervisor:start_child(sup_test, B4),
-    {error, _} = supervisor:start_child(sup_test, B5),
     {error, {invalid_modules,dy}}
-	= supervisor:start_child(sup_test, B6),
+	= supervisor:start_child(sup_test, B5),
 
     {error, {invalid_mfa,mfa}} = supervisor:check_childspecs([B1]),
     {error, {invalid_restart_type,prmanent}} =
@@ -487,15 +487,15 @@ child_specs(Config) when is_list(Config) ->
     {error, {invalid_shutdown,-10}} = supervisor:check_childspecs([B3]),
     {error, {invalid_child_type,wrker}}
 	= supervisor:check_childspecs([B4]),
-    {error, _} = supervisor:check_childspecs([B5]),
-    {error, {invalid_modules,dy}} = supervisor:check_childspecs([B6]),
+    {error, {invalid_modules,dy}} = supervisor:check_childspecs([B5]),
     {error, {invalid_module, 1}} =
-	supervisor:check_childspecs([B7]),
+	supervisor:check_childspecs([B6]),
 
     ok = supervisor:check_childspecs([C1]),
     ok = supervisor:check_childspecs([C2]),
     ok = supervisor:check_childspecs([C3]),
     ok = supervisor:check_childspecs([C4]),
+    ok = supervisor:check_childspecs([C5]),
     ok.
 
 %%-------------------------------------------------------------------------
diff --git a/system/doc/design_principles/sup_princ.xml b/system/doc/design_principles/sup_princ.xml
index 2748f21bbe..42d9f3e3d8 100644
--- a/system/doc/design_principles/sup_princ.xml
+++ b/system/doc/design_principles/sup_princ.xml
@@ -181,7 +181,8 @@ init(...) ->
            terminated using <c>exit(Child, kill)</c>.</item>
           <item>If the child process is another supervisor, it should be
            set to <c>infinity</c> to give the subtree enough time to
-           shutdown.</item>
+           shutdown. It is also allowed to set it to <c>infinity</c>, if the
+           child process is a worker.</item>
         </list>
       </item>
       <item>