src/os_cpu/aix_ppc/vm/os_aix_ppc.cpp

rev 12305 : 8169373: Work around linux NPTL stack guard error.
Summary: Also streamline OS guard page handling on linuxs390, linuxppc, aixppc.

*** 533,553 ****
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // thread stack
  
  size_t os::Posix::_compiler_thread_min_stack_allowed = 128 * K;
  size_t os::Posix::_java_thread_min_stack_allowed = 128 * K;
  size_t os::Posix::_vm_internal_thread_min_stack_allowed = 128 * K;
  
! // return default stack size for thr_type
  size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
!   // default stack size (compiler thread needs larger stack)
    size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
    return s;
  }
  
  /////////////////////////////////////////////////////////////////////////////
  // helper functions for fatal error handler
  
  void os::print_context(outputStream *st, const void *context) {
    if (context == NULL) return;
--- 533,567 ----
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // thread stack
  
+ // These sizes exclude OS stack guard pages, but include
+ // the VM guard pages.
  size_t os::Posix::_compiler_thread_min_stack_allowed = 128 * K;
  size_t os::Posix::_java_thread_min_stack_allowed = 128 * K;
  size_t os::Posix::_vm_internal_thread_min_stack_allowed = 128 * K;
  
! // Return default stack size for thr_type.
  size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
!   // Default stack size (compiler thread needs larger stack).
    size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
    return s;
  }
  
+ size_t os::Aix::default_guard_size(os::ThreadType thr_type) {
+   // Creating guard pages is very expensive. Java thread has HotSpot
+   // guard pages, so only enable libc guard pages for non-Java threads.
+   //
+   // Aix can have different page sizes for stack (4K) and heap (64K).
+   // As Hotspot knows only one page size, we assume the stack has 
+   // the same page size as the heap. Returning page_size() here can
+   // cause 16 guard pages which we want to avoid.  Thus we return 4K
+   // which will be rounded to the real page size by the OS.
+   return (thr_type == java_thread ? 0 : 4*K);
+ }
+ 
  /////////////////////////////////////////////////////////////////////////////
  // helper functions for fatal error handler
  
  void os::print_context(outputStream *st, const void *context) {
    if (context == NULL) return;