process.c (rb_f_exec): pause MJIT before replacing process

Non-parallel "make test-spec" caused
spec/ruby/core/process/wait2_spec.rb failures because mspec
uses "exec" in single-process mode, so there's no chance
the post-exec state could know about the MJIT child process
from its pre-exec state.

[ruby-core:87846] [Bug #14867]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63877 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

process.c

@@ -148,6 +148,10 @@ static void check_uid_switch(void);
 static void check_gid_switch(void);
 static int exec_async_signal_safe(const struct rb_execarg *, char *, size_t);
 
+/* mjit.c */
+extern int mjit_enabled;
+VALUE mjit_pause(void);
+
 #if 1
 #define p_uid_from_name p_uid_from_name
 #define p_gid_from_name p_gid_from_name
@@ -2849,6 +2853,7 @@ rb_f_exec(int argc, const VALUE *argv)
 
     execarg_obj = rb_execarg_new(argc, argv, TRUE, FALSE);
     eargp = rb_execarg_get(execarg_obj);
+    if (mjit_enabled) mjit_pause(); /* do not leak children */
     before_exec(); /* stop timer thread before redirects */
     rb_execarg_parent_start(execarg_obj);
     fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;

spec/ruby/core/process/wait2_spec.rb

@@ -15,8 +15,7 @@ describe "Process.wait2" do
       $stderr.puts "leaked before wait2 specs: #{leaked}" unless leaked.empty?
       with_feature :mjit do
         # Ruby-space should not see PIDs used by mjit
-        # TODO: Enable this once it succeeds with -DMJIT_FORCE_ENABLE
-        # leaked.should be_empty
+        leaked.should be_empty
       end
     rescue Errno::ECHILD # No child processes
     rescue NotImplementedError