signal.c: avoid repeated disable/enable interrupt

We only install system-level signal handlers during init (before any
threads or user code is running), so there's no need to repeatedly
enable/disable the interrupts at that time.  We also do not change
system-level sig handlers once user-level code is running.

This saves about 20 syscalls at startup and makes the executable
smaller (numbers from 32-bit x86):

        text       data     bss     dec     hex filename
before: 2815726   12100   30552 2858378  2b9d8a ruby
 after: 2815022   12100   30552 2857674  2b9aca ruby

* signal.c (install_sighandler): remove rb_disable_interrupt and
  rb_enable_interrupt calls
  (init_sigchld): ditto
  (Init_signal): disable and enable interrupt once around all
  install_sighandler and init_sigchld to reduce syscalls at start
  [Feature #9345] [ruby-core:59480]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48178 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,12 @@
+Tue Oct 28 16:52:07 2014  Eric Wong  <e@80x24.org>
+
+	* signal.c (install_sighandler): remove rb_disable_interrupt and
+	  rb_enable_interrupt calls
+	  (init_sigchld): ditto
+	  (Init_signal): disable and enable interrupt once around all
+	  install_sighandler and init_sigchld to reduce syscalls at start
+	  [Feature #9345] [ruby-core:59480]
+
 Tue Oct 28 16:22:41 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ruby.c (process_options, load_file_internal2): should not

signal.c

@@ -1298,15 +1298,12 @@ install_sighandler(int signum, sighandler_t handler)
 {
     sighandler_t old;
 
-    /* At this time, there is no subthread. Then sigmask guarantee atomics. */
-    rb_disable_interrupt();
     old = ruby_signal(signum, handler);
     if (old == SIG_ERR) return -1;
     /* signal handler should be inherited during exec. */
     if (old != SIG_DFL) {
 	ruby_signal(signum, old);
     }
-    rb_enable_interrupt();
     return 0;
 }
 #ifndef __native_client__
@@ -1319,7 +1316,6 @@ init_sigchld(int sig)
 {
     sighandler_t oldfunc;
 
-    rb_disable_interrupt();
     oldfunc = ruby_signal(sig, SIG_DFL);
     if (oldfunc == SIG_ERR) return -1;
     if (oldfunc != SIG_DFL && oldfunc != SIG_IGN) {
@@ -1328,7 +1324,6 @@ init_sigchld(int sig)
     else {
 	GET_VM()->trap_list[sig].cmd = 0;
     }
-    rb_enable_interrupt();
     return 0;
 }
 #  ifndef __native_client__
@@ -1405,6 +1400,9 @@ Init_signal(void)
     rb_alias(rb_eSignal, rb_intern_const("signm"), rb_intern_const("message"));
     rb_define_method(rb_eInterrupt, "initialize", interrupt_init, -1);
 
+    /* At this time, there is no subthread. Then sigmask guarantee atomics. */
+    rb_disable_interrupt();
+
     install_sighandler(SIGINT, sighandler);
 #ifdef SIGHUP
     install_sighandler(SIGHUP, sighandler);
@@ -1448,4 +1446,6 @@ Init_signal(void)
 #elif defined(SIGCHLD)
     init_sigchld(SIGCHLD);
 #endif
+
+    rb_enable_interrupt();
 }