process: block/unblock signals around fork

As with forking for execve(2) in `spawn', we must block signals
to ensure they are handled correctly in a freshly `fork'-ed child.

* process.c (retry_fork_ruby): block/unblock signals around fork
  (rb_fork_ruby): re-enable signals in forked child
* test/ruby/test_process.rb (test_forked_child_signal): new test
  [ruby-core:82883] [Bug #13916]

  Thanks to Russell Davis for the bug report and test case.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59975 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

process.c

@@ -3633,7 +3633,7 @@ rb_fork_async_signal_safe(int *status, int (*chfunc)(void*, char *, size_t), voi
 }
 
 static rb_pid_t
-retry_fork_ruby(int *status)
+retry_fork_ruby(int *status, struct child_handler_disabler_state *old)
 {
     rb_pid_t pid;
     int try_gc = 1;
@@ -3641,10 +3641,12 @@ retry_fork_ruby(int *status)
     while (1) {
         prefork();
         before_fork_ruby();
+        disable_child_handler_before_fork(old);
         pid = fork();
         if (pid == 0) /* fork succeed, child process */
             return pid;
         preserving_errno(after_fork_ruby());
+        preserving_errno(disable_child_handler_fork_parent(old));
         if (0 < pid) /* fork succeed, parent process */
             return pid;
         /* fork failed */
@@ -3657,14 +3659,16 @@ rb_pid_t
 rb_fork_ruby(int *status)
 {
     rb_pid_t pid;
+    struct child_handler_disabler_state old;
 
     if (status) *status = 0;
 
-    pid = retry_fork_ruby(status);
+    pid = retry_fork_ruby(status, &old);
     if (pid < 0)
         return pid;
     if (!pid) {
         after_fork_ruby();
+        disable_child_handler_fork_parent(&old); /* yes, bad name */
     }
     return pid;
 }

test/ruby/test_process.rb

@@ -2329,4 +2329,14 @@ EOS
       end
     end
   end
+
+  def test_forked_child_handles_signal
+    skip "fork not supported" unless Process.respond_to?(:fork)
+    assert_normal_exit(<<-"end;", '[ruby-core:82883] [Bug #13916]')
+      require 'timeout'
+      pid = fork { sleep }
+      Process.kill(:TERM, pid)
+      assert_equal pid, Timeout.timeout(30) { Process.wait(pid) }
+    end;
+  end
 end