--- a/src/hotspot/share/gc/shared/oopStorage.cpp Thu Aug 23 12:57:40 2018 -0700
+++ b/src/hotspot/share/gc/shared/oopStorage.cpp Thu Aug 23 18:14:53 2018 -0400
@@ -43,7 +43,6 @@
#include "utilities/globalDefinitions.hpp"
#include "utilities/macros.hpp"
#include "utilities/ostream.hpp"
-#include "utilities/spinYield.hpp"
OopStorage::AllocationListEntry::AllocationListEntry() : _prev(NULL), _next(NULL) {}
@@ -495,48 +494,6 @@
return true;
}
-OopStorage::ProtectActive::ProtectActive() : _enter(0), _exit() {}
-
-// Begin read-side critical section.
-uint OopStorage::ProtectActive::read_enter() {
- return Atomic::add(2u, &_enter);
-}
-
-// End read-side critical section.
-void OopStorage::ProtectActive::read_exit(uint enter_value) {
- Atomic::add(2u, &_exit[enter_value & 1]);
-}
-
-// Wait until all readers that entered the critical section before
-// synchronization have exited that critical section.
-void OopStorage::ProtectActive::write_synchronize() {
- SpinYield spinner;
- // Determine old and new exit counters, based on bit0 of the
- // on-entry _enter counter.
- uint value = OrderAccess::load_acquire(&_enter);
- volatile uint* new_ptr = &_exit[(value + 1) & 1];
- // Atomically change the in-use exit counter to the new counter, by
- // adding 1 to the _enter counter (flipping bit0 between 0 and 1)
- // and initializing the new exit counter to that enter value. Note:
- // The new exit counter is not being used by read operations until
- // this change succeeds.
- uint old;
- do {
- old = value;
- *new_ptr = ++value;
- value = Atomic::cmpxchg(value, &_enter, old);
- } while (old != value);
- // Readers that entered the critical section before we changed the
- // selected exit counter will use the old exit counter. Readers
- // entering after the change will use the new exit counter. Wait
- // for all the critical sections started before the change to
- // complete, e.g. for the value of old_ptr to catch up with old.
- volatile uint* old_ptr = &_exit[old & 1];
- while (old != OrderAccess::load_acquire(old_ptr)) {
- spinner.wait();
- }
-}
-
// Make new_array the _active_array. Increments new_array's refcount
// to account for the new reference. The assignment is atomic wrto
// obtain_active_array; once this function returns, it is safe for the
@@ -548,7 +505,10 @@
// Install new_array, ensuring its initialization is complete first.
OrderAccess::release_store(&_active_array, new_array);
// Wait for any readers that could read the old array from _active_array.
- _protect_active.write_synchronize();
+ // Can't use GlobalCounter here, because this is called from allocate(),
+ // which may be called in the scope of a GlobalCounter critical section
+ // when inserting a StringTable entry.
+ _protect_active.synchronize();
// All obtain critical sections that could see the old array have
// completed, having incremented the refcount of the old array. The
// caller can now safely relinquish the old array.
@@ -560,10 +520,9 @@
// _active_array. The caller must relinquish the array when done
// using it.
OopStorage::ActiveArray* OopStorage::obtain_active_array() const {
- uint enter_value = _protect_active.read_enter();
+ SingleWriterSynchronizer::CriticalSection cs(&_protect_active);
ActiveArray* result = OrderAccess::load_acquire(&_active_array);
result->increment_refcount();
- _protect_active.read_exit(enter_value);
return result;
}