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src/hotspot/share/runtime/objectMonitor.hpp
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rev 56634 : imported patch 8230876.patch
rev 56635 : v2.00 -> v2.05 (CR5/v2.05/8-for-jdk13) patches combined into one; merge with 8229212.patch; merge with jdk-14+11; merge with 8230184.patch; merge with 8230876.patch; merge with jdk-14+15; merge with jdk-14+18.
rev 56637 : Add OM_CACHE_LINE_SIZE so that ObjectMonitor cache line sizes can be experimented with independently of DEFAULT_CACHE_LINE_SIZE; for SPARC and X64 configs that use 128 for DEFAULT_CACHE_LINE_SIZE, we are experimenting with 64; move _previous_owner_tid and _allocation_state fields to share the cache line with ObjectMonitor::_header; put ObjectMonitor::_ref_count on its own cache line after _owner; add 'int* count_p' parameter to deflate_monitor_list() and deflate_monitor_list_using_JT() and push counter updates down to where the ObjectMonitors are actually removed from the in-use lists; monitors_iterate() async deflation check should use negative ref_count; add 'JavaThread* target' param to deflate_per_thread_idle_monitors_using_JT() add deflate_common_idle_monitors_using_JT() to make it clear which JavaThread* is the target of the work and which is the calling JavaThread* (self); g_free_list, g_om_in_use_list and g_om_in_use_count are now static to synchronizer.cpp (reduce scope); add more diagnostic info to some assert()'s; minor code cleanups and code motion; save_om_ptr() should detect a race with a deflating thread that is bailing out and cause a retry when the ref_count field is not positive; merge with jdk-14+11; add special GC support for TestHumongousClassLoader.java; merge with 8230184.patch; merge with jdk-14+14; merge with jdk-14+18.
rev 56638 : Merge the remainder of the lock-free monitor list changes from v2.06 with v2.06a and v2.06b after running the changes through the edit scripts; merge pieces from dcubed.monitor_deflate_conc.v2.06d in dcubed.monitor_deflate_conc.v2.06[ac]; merge pieces from dcubed.monitor_deflate_conc.v2.06e into dcubed.monitor_deflate_conc.v2.06c; merge with jdk-14+11; test work around for test/jdk/tools/jlink/multireleasejar/JLinkMultiReleaseJarTest.java should not been needed anymore; merge with jdk-14+18.
rev 56639 : loosen a couple more counter checks due to races observed in testing; simplify om_release() extraction of mid since list head or cur_mid_in_use is marked; simplify deflate_monitor_list() extraction of mid since there are no parallel deleters due to the safepoint; simplify deflate_monitor_list_using_JT() extraction of mid since list head or cur_mid_in_use is marked; prepend_block_to_lists() - simplify based on David H's comments; does not need load_acquire() or release_store() because of the cmpxchg(); prepend_to_common() - simplify to use mark_next_loop() for m and use mark_list_head() and release_store() for the non-empty list case; add more debugging for "Non-balanced monitor enter/exit" failure mode; fix race in inflate() in the "CASE: neutral" code path; install_displaced_markword_in_object() does not need to clear the header field since that is handled when the ObjectMonitor is moved from the global free list; LSuccess should clear boxReg to set ICC.ZF=1 to avoid depending on existing boxReg contents; update fast_unlock() to detect when object no longer refers to the same ObjectMonitor and take fast path exit instead; clarify fast_lock() code where we detect when object no longer refers to the same ObjectMonitor; add/update comments for movptr() calls where we move a literal into an Address; remove set_owner(); refactor setting of owner field into set_owner_from(2 versions), set_owner_from_BasicLock(), and try_set_owner_from(); the new functions include monitorinflation+owner logging; extract debug code from v2.06 and v2.07 and move to v2.07.debug; change 'jccb' -> 'jcc' and 'jmpb' -> 'jmp' as needed; checkpoint initial version of MacroAssembler::inc_om_ref_count(); update LP64 MacroAssembler::fast_lock() and fast_unlock() to use inc_om_ref_count(); fast_lock() return flag setting logic can use 'testptr(tmpReg, tmpReg)' instead of 'cmpptr(tmpReg, 0)' since that's more efficient; fast_unlock() LSuccess return flag setting logic can use 'testl (boxReg, 0)' instead of 'xorptr(boxReg, boxReg)' since that's more efficient; cleanup "fast-path" vs "fast path" and "slow-path" vs "slow path"; update MacroAssembler::rtm_inflated_locking() to use inc_om_ref_count(); update MacroAssembler::fast_lock() to preserve the flags before decrementing ref_count and restore the flags afterwards; this is more clean than depending on the contents of rax/tmpReg; coleenp CR - refactor async monitor deflation work from ServiceThread::service_thread_entry() to ObjectSynchronizer::deflate_idle_monitors_using_JT(); rehn,eosterlund CR - add support for HandshakeAfterDeflateIdleMonitors for platforms that don't have ObjectMonitor ref_count support implemented in C2 fast_lock() and fast_unlock().
@@ -118,34 +118,58 @@
//
// - The _recursions field should be of type int, or int32_t but not
// intptr_t. There's no reason to use a 64-bit type for this field
// in a 64-bit JVM.
+#ifndef OM_CACHE_LINE_SIZE
+// Use DEFAULT_CACHE_LINE_SIZE if not already specified for
+// the current build platform.
+#define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
+#endif
+
class ObjectMonitor {
+ friend class ObjectMonitorHandle;
friend class ObjectSynchronizer;
friend class ObjectWaiter;
friend class VMStructs;
JVMCI_ONLY(friend class JVMCIVMStructs;)
// The sync code expects the header field to be at offset zero (0).
// Enforced by the assert() in header_addr().
volatile markWord _header; // displaced object header word - mark
void* volatile _object; // backward object pointer - strong root
- public:
- ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
- private:
+ typedef enum {
+ Free = 0, // Free must be 0 for monitor to be free after memset(..,0,..).
+ New,
+ Old
+ } AllocationState;
+ AllocationState _allocation_state;
// Separate _header and _owner on different cache lines since both can
- // have busy multi-threaded access. _header and _object are set at
- // initial inflation and _object doesn't change until deflation so
- // _object is a good choice to share the cache line with _header.
- // _next_om shares _header's cache line for pre-monitor list historical
- // reasons. _next_om only changes if the next ObjectMonitor is deflated.
- DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE,
- sizeof(volatile markWord) + sizeof(void* volatile) +
- sizeof(ObjectMonitor *));
+ // have busy multi-threaded access. _header, _object and _allocation_state
+ // are set at initial inflation. _object and _allocation_state don't
+ // change until deflation so _object and _allocation_state are good
+ // choices to share the cache line with _header.
+ DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
+ sizeof(void* volatile) + sizeof(AllocationState));
+ // Used by async deflation as a marker in the _owner field:
+ #define DEFLATER_MARKER reinterpret_cast<void*>(-1)
void* volatile _owner; // pointer to owning thread OR BasicLock
volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
+ // Separate _owner and _ref_count on different cache lines since both
+ // can have busy multi-threaded access. _previous_owner_tid is only
+ // changed by ObjectMonitor::exit() so it is a good choice to share the
+ // cache line with _owner.
+ DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
+ sizeof(volatile jlong));
+ volatile jint _ref_count; // ref count for ObjectMonitor* and used by the async deflation
+ // protocol. See ObjectSynchronizer::deflate_monitor_using_JT().
+ // Separate _ref_count and _next_om on different cache lines since
+ // both can have busy multi-threaded access.
+ DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(volatile jint));
+ public: // for static synchronizer.cpp access:
+ ObjectMonitor* volatile _next_om; // Next ObjectMonitor* linkage
+ private:
volatile intptr_t _recursions; // recursion count, 0 for first entry
ObjectWaiter* volatile _EntryList; // Threads blocked on entry or reentry.
// The list is actually composed of WaitNodes,
// acting as proxies for Threads.
@@ -156,11 +180,12 @@
volatile int _Spinner; // for exit->spinner handoff optimization
volatile int _SpinDuration;
volatile jint _contentions; // Number of active contentions in enter(). It is used by is_busy()
// along with other fields to determine if an ObjectMonitor can be
- // deflated. See ObjectSynchronizer::deflate_monitor().
+ // deflated. See ObjectSynchronizer::deflate_monitor() and
+ // ObjectSynchronizer::deflate_monitor_using_JT().
protected:
ObjectWaiter* volatile _WaitSet; // LL of threads wait()ing on the monitor
volatile jint _waiters; // number of waiting threads
private:
volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
@@ -198,10 +223,11 @@
// TODO-FIXME: the "offset" routines should return a type of off_t instead of int ...
// ByteSize would also be an appropriate type.
static int header_offset_in_bytes() { return offset_of(ObjectMonitor, _header); }
static int object_offset_in_bytes() { return offset_of(ObjectMonitor, _object); }
static int owner_offset_in_bytes() { return offset_of(ObjectMonitor, _owner); }
+ static int ref_count_offset_in_bytes() { return offset_of(ObjectMonitor, _ref_count); }
static int recursions_offset_in_bytes() { return offset_of(ObjectMonitor, _recursions); }
static int cxq_offset_in_bytes() { return offset_of(ObjectMonitor, _cxq); }
static int succ_offset_in_bytes() { return offset_of(ObjectMonitor, _succ); }
static int EntryList_offset_in_bytes() { return offset_of(ObjectMonitor, _EntryList); }
@@ -223,18 +249,40 @@
volatile markWord* header_addr();
void set_header(markWord hdr);
intptr_t is_busy() const {
// TODO-FIXME: assert _owner == null implies _recursions = 0
- return _contentions|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList);
+ // We do not include _ref_count in the is_busy() check because
+ // _ref_count is for indicating that the ObjectMonitor* is in
+ // use which is orthogonal to whether the ObjectMonitor itself
+ // is in use for a locking operation.
+ intptr_t ret_code = _contentions | _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
+ if (!AsyncDeflateIdleMonitors) {
+ ret_code |= intptr_t(_owner);
+ } else {
+ if (_owner != DEFLATER_MARKER) {
+ ret_code |= intptr_t(_owner);
+ }
+ }
+ return ret_code;
}
const char* is_busy_to_string(stringStream* ss);
intptr_t is_entered(Thread* current) const;
- void* owner() const;
- void set_owner(void* owner);
+ void* owner() const; // Returns NULL if DEFLATER_MARKER is observed.
+ // Returns true if owner field == DEFLATER_MARKER and false otherwise.
+ bool owner_is_DEFLATER_MARKER();
+ // Set _owner field to new_value; current value must match old_value.
+ void set_owner_from(void* new_value, void* old_value);
+ // Set _owner field to new_value; current value must match old_value1 or old_value2.
+ void set_owner_from(void* new_value, void* old_value1, void* old_value2);
+ // Set _owner field to self; current value must match basic_lock_p.
+ void set_owner_from_BasicLock(Thread* self, void* basic_lock_p);
+ // Try to set _owner field to new_value if the current value matches
+ // old_value. Otherwise, does not change the _owner field.
+ void* try_set_owner_from(void* new_value, void* old_value);
jint waiters() const;
jint contentions() const;
intptr_t recursions() const { return _recursions; }
@@ -261,11 +309,11 @@
// _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
// _contentions == 0 EntryList == NULL
// _recursions == 0 _WaitSet == NULL
DEBUG_ONLY(stringStream ss;)
assert((is_busy() | _recursions) == 0, "freeing in-use monitor: %s, "
- "recursions=" INTPTR_FORMAT, is_busy_to_string(&ss), _recursions);
+ "recursions=" INTX_FORMAT, is_busy_to_string(&ss), _recursions);
_succ = NULL;
_EntryList = NULL;
_cxq = NULL;
_WaitSet = NULL;
_recursions = 0;
@@ -274,23 +322,34 @@
public:
void* object() const;
void* object_addr();
void set_object(void* obj);
+ void set_allocation_state(AllocationState s);
+ AllocationState allocation_state() const;
+ bool is_free() const;
+ bool is_active() const;
+ bool is_old() const;
+ bool is_new() const;
+ void dec_ref_count();
+ void inc_ref_count();
+ jint ref_count() const;
// Returns true if the specified thread owns the ObjectMonitor. Otherwise
// returns false and throws IllegalMonitorStateException (IMSE).
bool check_owner(Thread* THREAD);
void clear();
+ void clear_using_JT();
void enter(TRAPS);
void exit(bool not_suspended, TRAPS);
void wait(jlong millis, bool interruptable, TRAPS);
void notify(TRAPS);
void notifyAll(TRAPS);
void print() const;
+ void print_debug_style_on(outputStream* st) const;
void print_on(outputStream* st) const;
// Use the following at your own risk
intptr_t complete_exit(TRAPS);
void reenter(intptr_t recursions, TRAPS);
@@ -302,12 +361,44 @@
void DequeueSpecificWaiter(ObjectWaiter* waiter);
void EnterI(TRAPS);
void ReenterI(Thread* self, ObjectWaiter* self_node);
void UnlinkAfterAcquire(Thread* self, ObjectWaiter* self_node);
int TryLock(Thread* self);
- int NotRunnable(Thread* self, Thread * Owner);
+ int NotRunnable(Thread* self, Thread* Owner);
int TrySpin(Thread* self);
void ExitEpilog(Thread* self, ObjectWaiter* Wakee);
bool ExitSuspendEquivalent(JavaThread* self);
+ void install_displaced_markword_in_object(const oop obj);
};
+// A helper object for managing an ObjectMonitor*'s ref_count. There
+// are special safety considerations when async deflation is used.
+class ObjectMonitorHandle : public StackObj {
+ private:
+ ObjectMonitor* _om_ptr;
+ public:
+ ObjectMonitorHandle() { _om_ptr = NULL; }
+ ~ObjectMonitorHandle();
+
+ ObjectMonitor* om_ptr() const { return _om_ptr; }
+ // Save the ObjectMonitor* associated with the specified markWord and
+ // increment the ref_count.
+ bool save_om_ptr(oop object, markWord mark);
+
+ // For internal used by ObjectSynchronizer::monitors_iterate().
+ ObjectMonitorHandle(ObjectMonitor* _om_ptr);
+ // For internal use by ObjectSynchronizer::inflate().
+ void set_om_ptr(ObjectMonitor* om_ptr);
+};
+
+// Macro to use guarantee() for more strict AsyncDeflateIdleMonitors
+// checks and assert() otherwise.
+#define ADIM_guarantee(p, ...) \
+ do { \
+ if (AsyncDeflateIdleMonitors) { \
+ guarantee(p, __VA_ARGS__); \
+ } else { \
+ assert(p, __VA_ARGS__); \
+ } \
+ } while (0)
+
#endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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