src/share/vm/memory/metaspace.cpp

rev 6878 : 8049599: MetaspaceGC::_capacity_until_GC can overflow

*** 1413,1423 ****
  }
  
  size_t MetaspaceGC::inc_capacity_until_GC(size_t v) {
    assert_is_size_aligned(v, Metaspace::commit_alignment());
  
!   return (size_t)Atomic::add_ptr(v, &_capacity_until_GC);
  }
  
  size_t MetaspaceGC::dec_capacity_until_GC(size_t v) {
    assert_is_size_aligned(v, Metaspace::commit_alignment());
  
--- 1413,1445 ----
  }
  
  size_t MetaspaceGC::inc_capacity_until_GC(size_t v) {
    assert_is_size_aligned(v, Metaspace::commit_alignment());
  
!   size_t capacity_until_GC = (size_t) _capacity_until_GC;
!   size_t new_value = capacity_until_GC + v;
! 
!   if (new_value < capacity_until_GC) {
!     // the addition wrapped around, set new_value to max value
!     new_value = max_uintx;
!   }
! 
!   bool cas_succeeded = false;
!   size_t num_retries = 5; // just to limit the number of CAS attempts
!   for (size_t i = 0; i < num_retries; i++) {
!     intptr_t cmp = (intptr_t) capacity_until_GC;
!     intptr_t swap = (intptr_t) new_value;
!     intptr_t prev = Atomic::cmpxchg_ptr(swap, &_capacity_until_GC, cmp);
! 
!     if (prev == cmp) {
!       cas_succeeded = true;
!       break;
!     }
!   }
! 
!   // if the CAS did not succeed, just return the current value
!   return cas_succeeded ? new_value : _capacity_until_GC;
  }
  
  size_t MetaspaceGC::dec_capacity_until_GC(size_t v) {
    assert_is_size_aligned(v, Metaspace::commit_alignment());