process.c: do not run signal handler before fork

to prevent from proceeding one for MJIT while it's not safe yet.
By that situation, MJIT worker could be waiting for compiler process forever
http://ci.rvm.jp/results/trunk-mjit@silicon-docker/1468033

[Bug #15320]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65807 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

internal.h

@@ -1633,6 +1633,7 @@ VALUE rb_math_sqrt(VALUE);
 #if USE_MJIT
 extern int mjit_enabled;
 VALUE mjit_pause(int wait_p);
+void mjit_pause_without_ints(void);
 VALUE mjit_resume(void);
 #else
 #define mjit_enabled 0

mjit.c

@@ -677,7 +677,7 @@ mjit_init(struct mjit_options *opts)
 }
 
 static void
-stop_worker(void)
+stop_worker(int check_ints_p)
 {
     rb_execution_context_t *ec = GET_EC();
 
@@ -687,10 +687,17 @@ stop_worker(void)
         stop_worker_p = TRUE; /* Setting this inside loop because RUBY_VM_CHECK_INTS may make this FALSE. */
         rb_native_cond_broadcast(&mjit_worker_wakeup);
         CRITICAL_SECTION_FINISH(3, "in stop_worker");
-        RUBY_VM_CHECK_INTS(ec);
+        if (check_ints_p) RUBY_VM_CHECK_INTS(ec);
     }
 }
 
+/* A function to stop MJIT worker when it's not safe to allow interrupts. */
+void
+mjit_pause_without_ints(void)
+{
+    stop_worker(FALSE);
+}
+
 /* Stop JIT-compiling methods but compiled code is kept available. */
 VALUE
 mjit_pause(int wait_p)
@@ -716,7 +723,7 @@ mjit_pause(int wait_p)
         }
     }
 
-    stop_worker();
+    stop_worker(TRUE);
     return Qtrue;
 }
 
@@ -809,7 +816,7 @@ mjit_finish(void)
     CRITICAL_SECTION_FINISH(3, "in mjit_finish to wakeup from pch");
 
     /* Stop worker */
-    stop_worker();
+    stop_worker(TRUE);
 
     rb_native_mutex_destroy(&mjit_engine_mutex);
     rb_native_cond_destroy(&mjit_pch_wakeup);

process.c

@@ -1506,8 +1506,9 @@ static void
 before_fork_ruby(void)
 {
     if (mjit_enabled) {
-        /* avoid leaving locked mutex and units being modified for child process. */
-        mjit_pause(FALSE);
+        /* Avoid leaving locked mutex and units being modified for child process. Here may not be
+           safe for proceeding SIGCHLD handler, so this does not allow RUBY_VM_CHECK_INTS. */
+        mjit_pause_without_ints();
     }
 
     before_exec();