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src/hotspot/share/runtime/objectMonitor.inline.hpp

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rev 57587 : imported patch 8236035.patch.cr0
rev 57588 : dholmes CR - rename simply_set_owner_from() -> set_owner_from() and simply_set_owner_from_BasicLock() -> set_owner_from_BasicLock(); rename release_clear_owner_with_barrier() -> release_clear_owner() and refactor barrier code back into the call sites.
rev 57589 : kbarrett CR - rearrange some loads of _owner field to be more efficient; clarify header comment for try_set_owner_from() declaration; make some loads of _owner field DEBUG_ONLY since they only exist for assert()'s; update related logging calls to use the existing function parameter instead.
rev 57590 : dholmes CR - simplify comment for try_set_owner_from(); self-review: add return value comment to try_set_owner_from() definition.
rev 57593 : coleenp CR part1: add ObjectMonitor::next_om(), set_next_om(), and try_set_next_om(); ObjectMonitor::_next_om field is now private; rename ListGlobals -> ObjectMonitorListGlobals, rename LVars -> om_list_globals, and prefix each ObjectMonitorListGlobals field with '_'; delete static set_next() function; clarify comments; coleenp CR part2: delete stale comments about mux*().
rev 57594 : coleenp CR: add comment to explain why _next_om field uses Atomic ops.
rev 57595 : v2.09a with 8235795, 8235931 and 8236035 extracted; rebased to jdk-14+28; merge with 8236035.patch.cr1; merge with 8235795.patch.cr1; merge with 8236035.patch.cr2; merge with 8235795.patch.cr2; merge with 8235795.patch.cr3.

@@ -23,10 +23,11 @@
  */
 
 #ifndef SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP
 #define SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP
 
+#include "logging/log.hpp"
 #include "runtime/atomic.hpp"
 
 inline intptr_t ObjectMonitor::is_entered(TRAPS) const {
   if (THREAD == _owner || THREAD->is_lock_owned((address) _owner)) {
     return 1;

@@ -49,23 +50,61 @@
 
 inline jint ObjectMonitor::waiters() const {
   return _waiters;
 }
 
+// Returns NULL if DEFLATER_MARKER is observed.
 inline void* ObjectMonitor::owner() const {
-  return _owner;
+  void* owner = _owner;
+  return owner != DEFLATER_MARKER ? owner : NULL;
+}
+
+// Returns true if owner field == DEFLATER_MARKER and false otherwise.
+// This accessor is called when we really need to know if the owner
+// field == DEFLATER_MARKER and any non-NULL value won't do the trick.
+inline bool ObjectMonitor::owner_is_DEFLATER_MARKER() {
+  return _owner == DEFLATER_MARKER;
 }
 
 inline void ObjectMonitor::clear() {
   assert(Atomic::load(&_header).value() != 0, "must be non-zero");
+  assert(_owner == NULL, "must be NULL: owner=" INTPTR_FORMAT, p2i(_owner));
+#ifdef ASSERT
+  jint l_ref_count = ref_count();
+#endif
+  assert(l_ref_count == 0, "must be 0: l_ref_count=%d, ref_count=%d", l_ref_count, ref_count());
+
+  Atomic::store(&_header, markWord::zero());
+
+  clear_using_JT();
+}
+
+inline void ObjectMonitor::clear_using_JT() {
+  // Unlike other *_using_JT() functions, we cannot assert
+  // AsyncDeflateIdleMonitors or Thread::current()->is_Java_thread()
+  // because clear() calls this function for the rest of its checks.
+
+  if (AsyncDeflateIdleMonitors) {
+    // Async deflation protocol uses the header, owner and ref_count
+    // fields. While the ObjectMonitor being deflated is on the global free
+    // list, we leave those three fields alone; owner == DEFLATER_MARKER
+    // and ref_count < 0 will force any racing threads to retry. The
+    // header field is used by install_displaced_markword_in_object()
+    // in the last part of the deflation protocol so we cannot check
+    // its value here.
+    guarantee(_owner == NULL || _owner == DEFLATER_MARKER,
+              "must be NULL or DEFLATER_MARKER: owner=" INTPTR_FORMAT,
+              p2i(_owner));
+    jint l_ref_count = ref_count();
+    guarantee(l_ref_count <= 0, "must be <= 0: l_ref_count=%d, ref_count=%d", l_ref_count, ref_count());
+  }
   assert(_contentions == 0, "must be 0: contentions=%d", _contentions);
   assert(_waiters == 0, "must be 0: waiters=%d", _waiters);
   assert(_recursions == 0, "must be 0: recursions=" INTX_FORMAT, _recursions);
   assert(_object != NULL, "must be non-NULL");
-  assert(_owner == NULL, "must be NULL: owner=" INTPTR_FORMAT, p2i(_owner));
 
-  Atomic::store(&_header, markWord::zero());
+  set_allocation_state(Free);
   _object = NULL;
 }
 
 inline void* ObjectMonitor::object() const {
   return _object;

@@ -82,10 +121,135 @@
 // return number of threads contending for this monitor
 inline jint ObjectMonitor::contentions() const {
   return _contentions;
 }
 
-inline void ObjectMonitor::set_owner(void* owner) {
-  _owner = owner;
+// Clear _owner field; current value must match old_value.
+inline void ObjectMonitor::release_clear_owner(void* old_value) {
+  void* prev = Atomic::load(&_owner);
+  ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
+                 ", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
+  Atomic::release_store(&_owner, (void*)NULL);
+  log_trace(monitorinflation, owner)("release_clear_owner(): mid="
+                                     INTPTR_FORMAT ", old_value=" INTPTR_FORMAT,
+                                     p2i(this), p2i(old_value));
+}
+
+// Simply set _owner field to new_value; current value must match old_value.
+// (Simple means no memory sync needed.)
+inline void ObjectMonitor::set_owner_from(void* old_value, void* new_value) {
+  void* prev = Atomic::load(&_owner);
+  ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
+                 ", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
+  Atomic::store(&_owner, new_value);
+  log_trace(monitorinflation, owner)("set_owner_from(): mid="
+                                     INTPTR_FORMAT ", old_value=" INTPTR_FORMAT
+                                     ", new_value=" INTPTR_FORMAT, p2i(this),
+                                     p2i(old_value), p2i(new_value));
+}
+
+// Simply set _owner field to new_value; current value must match old_value1 or old_value2.
+// (Simple means no memory sync needed.)
+inline void ObjectMonitor::set_owner_from(void* old_value1, void* old_value2, void* new_value) {
+  void* prev = Atomic::load(&_owner);
+  ADIM_guarantee(prev == old_value1 || prev == old_value2,
+                 "unexpected prev owner=" INTPTR_FORMAT ", expected1="
+                 INTPTR_FORMAT " or expected2=" INTPTR_FORMAT, p2i(prev),
+                 p2i(old_value1), p2i(old_value2));
+  _owner = new_value;
+  log_trace(monitorinflation, owner)("set_owner_from(old1=" INTPTR_FORMAT
+                                     ", old2=" INTPTR_FORMAT "): mid="
+                                     INTPTR_FORMAT ", prev=" INTPTR_FORMAT
+                                     ", new=" INTPTR_FORMAT, p2i(old_value1),
+                                     p2i(old_value2), p2i(this), p2i(prev),
+                                     p2i(new_value));
+}
+
+// Simply set _owner field to self; current value must match basic_lock_p.
+inline void ObjectMonitor::set_owner_from_BasicLock(void* basic_lock_p, Thread* self) {
+  void* prev = Atomic::load(&_owner);
+  ADIM_guarantee(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
+                 ", expected=" INTPTR_FORMAT, p2i(prev), p2i(basic_lock_p));
+  // Non-null owner field to non-null owner field is safe without
+  // cmpxchg() as long as all readers can tolerate either flavor.
+  Atomic::store(&_owner, self);
+  log_trace(monitorinflation, owner)("set_owner_from_BasicLock(): mid="
+                                     INTPTR_FORMAT ", basic_lock_p="
+                                     INTPTR_FORMAT ", new_value=" INTPTR_FORMAT,
+                                     p2i(this), p2i(basic_lock_p), p2i(self));
+}
+
+// Try to set _owner field to new_value if the current value matches
+// old_value. Otherwise, does not change the _owner field. Returns
+// the prior value of the _owner field.
+inline void* ObjectMonitor::try_set_owner_from(void* old_value, void* new_value) {
+  void* prev = Atomic::cmpxchg(&_owner, old_value, new_value);
+  if (prev == old_value) {
+    log_trace(monitorinflation, owner)("try_set_owner_from(): mid="
+                                       INTPTR_FORMAT ", prev=" INTPTR_FORMAT
+                                       ", new=" INTPTR_FORMAT, p2i(this),
+                                       p2i(prev), p2i(new_value));
+  }
+  return prev;
+}
+
+inline void ObjectMonitor::set_allocation_state(ObjectMonitor::AllocationState s) {
+  _allocation_state = s;
+}
+
+inline ObjectMonitor::AllocationState ObjectMonitor::allocation_state() const {
+  return _allocation_state;
+}
+
+inline bool ObjectMonitor::is_free() const {
+  return _allocation_state == Free;
+}
+
+inline bool ObjectMonitor::is_old() const {
+  return _allocation_state == Old;
+}
+
+inline bool ObjectMonitor::is_new() const {
+  return _allocation_state == New;
+}
+
+inline void ObjectMonitor::dec_ref_count() {
+  Atomic::dec(&_ref_count);
+  // Can be negative as part of async deflation protocol.
+  jint l_ref_count = ref_count();
+  ADIM_guarantee(AsyncDeflateIdleMonitors || l_ref_count >= 0,
+                 "sanity check: l_ref_count=%d, ref_count=%d", l_ref_count, ref_count());
+}
+
+inline void ObjectMonitor::inc_ref_count() {
+  Atomic::inc(&_ref_count);
+  // Can be negative as part of async deflation protocol.
+  jint l_ref_count = ref_count();
+  ADIM_guarantee(AsyncDeflateIdleMonitors || l_ref_count > 0,
+                 "sanity check: l_ref_count=%d, ref_count=%d", l_ref_count, ref_count());
+}
+
+inline jint ObjectMonitor::ref_count() const {
+  return Atomic::load(&_ref_count);
+}
+
+// The _next_om field can be concurrently read and modified so we
+// use Atomic operations to disable compiler optimizations that
+// might try to elide loading and/or storing this field.
+
+inline ObjectMonitor* ObjectMonitor::next_om() const {
+  return Atomic::load(&_next_om);
+}
+
+// Simply set _next_om field to new_value.
+inline void ObjectMonitor::set_next_om(ObjectMonitor* new_value) {
+  Atomic::store(&_next_om, new_value);
+}
+
+// Try to set _next_om field to new_value if the current value matches
+// old_value. Otherwise, does not change the _next_om field. Returns
+// the prior value of the _next_om field.
+inline ObjectMonitor* ObjectMonitor::try_set_next_om(ObjectMonitor* old_value, ObjectMonitor* new_value) {
+  return Atomic::cmpxchg(&_next_om, old_value, new_value);
 }
 
 #endif // SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP
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