src/hotspot/os/linux/os_linux.cpp

rev 49420 : 8199717: Avoid calculating primordial thread stack bounds on VM startup
Reviewed-by: dholmes, rehn, stuefe

*** 150,159 ****
--- 150,166 ----
  
  static jlong initial_time_count=0;
  
  static int clock_tics_per_sec = 100;
  
+ // If the VM might have been created on the primordial thread, we need to resolve the
+ // primordial thread stack bounds and check if the current thread might be the
+ // primordial thread in places. If we know that the primordial thread is never used,
+ // such as when the VM was created by one of the standard java launchers, we can
+ // avoid this
+ static bool suppress_primordial_thread_resolution = false;
+ 
  // For diagnostics to print a message once. see run_periodic_checks
  static sigset_t check_signal_done;
  static bool check_signals = true;
  
  // Signal number used to suspend/resume a thread
*** 915,924 ****
--- 922,934 ----
  //////////////////////////////////////////////////////////////////////////////
  // primordial thread
  
  // Check if current thread is the primordial thread, similar to Solaris thr_main.
  bool os::is_primordial_thread(void) {
+   if (suppress_primordial_thread_resolution) {
+     return false;
+   }
    char dummy;
    // If called before init complete, thread stack bottom will be null.
    // Can be called if fatal error occurs before initialization.
    if (os::Linux::initial_thread_stack_bottom() == NULL) return false;
    assert(os::Linux::initial_thread_stack_bottom() != NULL &&
*** 4934,4944 ****
--- 4944,4958 ----
  
    // Check and sets minimum stack sizes against command line options
    if (Posix::set_minimum_stack_sizes() == JNI_ERR) {
      return JNI_ERR;
    }
+ 
+   suppress_primordial_thread_resolution = Arguments::created_by_java_launcher();
+   if (!suppress_primordial_thread_resolution) {
      Linux::capture_initial_stack(JavaThread::stack_size_at_create());
+   }
  
  #if defined(IA32)
    workaround_expand_exec_shield_cs_limit();
  #endif