src/hotspot/os/linux/os_linux.cpp

*** 3104,3114 ****
  }
  
  bool os::committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size) {
    int mincore_return_value;
    const size_t stripe = 1024;  // query this many pages each time
!   unsigned char vec[stripe];
    const size_t page_sz = os::vm_page_size();
    size_t pages = size / page_sz;
  
    assert(is_aligned(start, page_sz), "Start address must be page aligned");
    assert(is_aligned(size, page_sz), "Size must be page aligned");
--- 3104,3117 ----
  }
  
  bool os::committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size) {
    int mincore_return_value;
    const size_t stripe = 1024;  // query this many pages each time
!   unsigned char vec[stripe + 1];
!   // set a guard
!   vec[stripe] = 'X';
! 
    const size_t page_sz = os::vm_page_size();
    size_t pages = size / page_sz;
  
    assert(is_aligned(start, page_sz), "Start address must be page aligned");
    assert(is_aligned(size, page_sz), "Size must be page aligned");
*** 3116,3126 ****
    committed_start = NULL;
  
    int loops = (pages + stripe - 1) / stripe;
    int committed_pages = 0;
    address loop_base = start;
!   for (int index = 0; index < loops; index ++) {
      assert(pages > 0, "Nothing to do");
      int pages_to_query = (pages >= stripe) ? stripe : pages;
      pages -= pages_to_query;
  
      // Get stable read
--- 3119,3131 ----
    committed_start = NULL;
  
    int loops = (pages + stripe - 1) / stripe;
    int committed_pages = 0;
    address loop_base = start;
!   bool found_range = false;
! 
!   for (int index = 0; index < loops && !found_range; index ++) {
      assert(pages > 0, "Nothing to do");
      int pages_to_query = (pages >= stripe) ? stripe : pages;
      pages -= pages_to_query;
  
      // Get stable read
*** 3131,3146 ****
--- 3136,3153 ----
      // Bailout and return as not committed for now.
      if (mincore_return_value == -1 && errno == ENOMEM) {
        return false;
      }
  
+     assert(vec[stripe] == 'X', "overflow guard");
      assert(mincore_return_value == 0, "Range must be valid");
      // Process this stripe
      for (int vecIdx = 0; vecIdx < pages_to_query; vecIdx ++) {
        if ((vec[vecIdx] & 0x01) == 0) { // not committed
          // End of current contiguous region
          if (committed_start != NULL) {
+           found_range = true;
            break;
          }
        } else { // committed
          // Start of region
          if (committed_start == NULL) {