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src/hotspot/share/runtime/objectMonitor.cpp
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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 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().
@@ -243,11 +243,11 @@
// The following code is ordered to check the most common cases first
// and to reduce RTS->RTO cache line upgrades on SPARC and IA32 processors.
Thread * const Self = THREAD;
- void * cur = Atomic::cmpxchg(Self, &_owner, (void*)NULL);
+ void* cur = try_set_owner_from(Self, NULL);
if (cur == NULL) {
assert(_recursions == 0, "invariant");
return;
}
@@ -258,18 +258,16 @@
}
if (Self->is_lock_owned ((address)cur)) {
assert(_recursions == 0, "internal state error");
_recursions = 1;
- // Commute owner from a thread-specific on-stack BasicLockObject address to
- // a full-fledged "Thread *".
- _owner = Self;
+ set_owner_from_BasicLock(Self, cur); // Convert from BasicLock* to Thread*.
return;
}
if (AsyncDeflateIdleMonitors &&
- Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
+ try_set_owner_from(Self, DEFLATER_MARKER) == DEFLATER_MARKER) {
// The deflation protocol finished the first part (setting owner),
// but it failed the second part (making ref_count negative) and
// bailed. Or the ObjectMonitor was async deflated and reused.
// Acquired the monitor.
assert(_recursions == 0, "invariant");
@@ -413,11 +411,11 @@
// Callers must compensate as needed.
int ObjectMonitor::TryLock(Thread * Self) {
void * own = _owner;
if (own != NULL) return 0;
- if (Atomic::replace_if_null(Self, &_owner)) {
+ if (try_set_owner_from(Self, NULL) == NULL) {
assert(_recursions == 0, "invariant");
return 1;
}
// The lock had been free momentarily, but we lost the race to the lock.
// Interference -- the CAS failed.
@@ -444,12 +442,12 @@
return;
}
markWord dmw = header();
if (dmw.value() == 0) {
- // ObjectMonitor's header/dmw has been cleared so the object's
- // header has already been restored.
+ // ObjectMonitor's header/dmw has been cleared so the ObjectMonitor
+ // has been deflated and taken off the global free list.
return;
}
// A non-NULL dmw has to be either neutral (not locked and not marked)
// or is already participating in this restoration protocol.
@@ -495,16 +493,10 @@
// into the object's header. The thread deflating the monitor just
// wanted the object's header restored and it is. The threads that
// detected a race with the deflation process also wanted the
// object's header restored before they retry their operation and
// because it is restored they will only retry once.
-
- if (marked_dmw.value() != 0) {
- // Clear _header to NULL if it is still marked_dmw so a racing
- // install_displaced_markword_in_object() can bail out sooner.
- Atomic::cmpxchg(markWord::zero(), &_header, marked_dmw);
- }
}
// Convert the fields used by is_busy() to a string that can be
// used for diagnostic output.
const char* ObjectMonitor::is_busy_to_string(stringStream* ss) {
@@ -537,11 +529,11 @@
assert(_Responsible != Self, "invariant");
return;
}
if (AsyncDeflateIdleMonitors &&
- Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
+ try_set_owner_from(Self, DEFLATER_MARKER) == DEFLATER_MARKER) {
// The deflation protocol finished the first part (setting owner),
// but it failed the second part (making ref_count negative) and
// bailed. Or the ObjectMonitor was async deflated and reused.
// Acquired the monitor.
assert(_succ != Self, "invariant");
@@ -664,11 +656,11 @@
}
if (TryLock(Self) > 0) break;
if (AsyncDeflateIdleMonitors &&
- Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
+ try_set_owner_from(Self, DEFLATER_MARKER) == DEFLATER_MARKER) {
// The deflation protocol finished the first part (setting owner),
// but it failed the second part (making ref_count negative) and
// bailed. Or the ObjectMonitor was async deflated and reused.
// Acquired the monitor.
break;
@@ -796,11 +788,11 @@
if (TryLock(Self) > 0) break;
if (TrySpin(Self) > 0) break;
if (AsyncDeflateIdleMonitors &&
- Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
+ try_set_owner_from(Self, DEFLATER_MARKER) == DEFLATER_MARKER) {
// The deflation protocol finished the first part (setting owner),
// but it failed the second part (making ref_count negative) and
// bailed. Or the ObjectMonitor was async deflated and reused.
// Acquired the monitor.
break;
@@ -993,17 +985,14 @@
// of such futile wakups is low.
void ObjectMonitor::exit(bool not_suspended, TRAPS) {
Thread * const Self = THREAD;
if (THREAD != _owner) {
- if (THREAD->is_lock_owned((address) _owner)) {
- // Transmute _owner from a BasicLock pointer to a Thread address.
- // We don't need to hold _mutex for this transition.
- // Non-null to Non-null is safe as long as all readers can
- // tolerate either flavor.
+ void* cur = _owner;
+ if (THREAD->is_lock_owned((address)cur)) {
assert(_recursions == 0, "invariant");
- _owner = THREAD;
+ set_owner_from_BasicLock(Self, cur); // Convert from BasicLock* to Thread*.
_recursions = 0;
} else {
// Apparent unbalanced locking ...
// Naively we'd like to throw IllegalMonitorStateException.
// As a practical matter we can neither allocate nor throw an
@@ -1011,12 +1000,18 @@
// see x86_32.ad Fast_Unlock() and the I1 and I2 properties.
// Upon deeper reflection, however, in a properly run JVM the only
// way we should encounter this situation is in the presence of
// unbalanced JNI locking. TODO: CheckJNICalls.
// See also: CR4414101
- assert(false, "Non-balanced monitor enter/exit! Likely JNI locking: "
- "owner=" INTPTR_FORMAT, p2i(_owner));
+ tty->print_cr("ERROR: ObjectMonitor::exit(): thread=" INTPTR_FORMAT
+ " is exiting an ObjectMonitor it does not own.",
+ p2i(THREAD));
+ tty->print_cr("The imbalance is possibly caused by JNI locking.");
+ print_debug_style_on(tty);
+ // Changing this from an assert() to ADIM_guarantee() may run
+ // afoul of any test that is inducing non-balanced JNI locking.
+ ADIM_guarantee(false, "Non-balanced monitor enter/exit!");
return;
}
}
if (_recursions != 0) {
@@ -1041,12 +1036,16 @@
// release semantics: prior loads and stores from within the critical section
// must not float (reorder) past the following store that drops the lock.
// On SPARC that requires MEMBAR #loadstore|#storestore.
// But of course in TSO #loadstore|#storestore is not required.
+ if (AsyncDeflateIdleMonitors) {
+ set_owner_from(NULL, Self);
+ } else {
OrderAccess::release_store(&_owner, (void*)NULL); // drop the lock
OrderAccess::storeload(); // See if we need to wake a successor
+ }
if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
return;
}
// Other threads are blocked trying to acquire the lock.
@@ -1084,11 +1083,11 @@
// Only the current lock owner can manipulate the EntryList or
// drain _cxq, so we need to reacquire the lock. If we fail
// to reacquire the lock the responsibility for ensuring succession
// falls to the new owner.
//
- if (!Atomic::replace_if_null(THREAD, &_owner)) {
+ if (try_set_owner_from(Self, NULL) != NULL) {
return;
}
guarantee(_owner == THREAD, "invariant");
@@ -1217,12 +1216,16 @@
// The thread associated with Wakee may have grabbed the lock and "Wakee" may be
// out-of-scope (non-extant).
Wakee = NULL;
// Drop the lock
+ if (AsyncDeflateIdleMonitors) {
+ set_owner_from(NULL, Self);
+ } else {
OrderAccess::release_store(&_owner, (void*)NULL);
OrderAccess::fence(); // ST _owner vs LD in unpark()
+ }
DTRACE_MONITOR_PROBE(contended__exit, this, object(), Self);
Trigger->unpark();
// Maintain stats and report events to JVMTI
@@ -1245,13 +1248,14 @@
JavaThread *jt = (JavaThread *)THREAD;
assert(InitDone, "Unexpectedly not initialized");
if (THREAD != _owner) {
- if (THREAD->is_lock_owned ((address)_owner)) {
+ void* cur = _owner;
+ if (THREAD->is_lock_owned((address)cur)) {
assert(_recursions == 0, "internal state error");
- _owner = THREAD; // Convert from basiclock addr to Thread addr
+ set_owner_from_BasicLock(Self, cur); // Convert from BasicLock* to Thread*.
_recursions = 0;
}
}
guarantee(Self == _owner, "complete_exit not owner");
@@ -1295,12 +1299,13 @@
// is not the owner, that exception will be replaced by the IMSE.
bool ObjectMonitor::check_owner(Thread* THREAD) {
if (_owner == THREAD) {
return true;
}
- if (THREAD->is_lock_owned((address)_owner)) {
- _owner = THREAD; // convert from BasicLock addr to Thread addr
+ void* cur = _owner;
+ if (THREAD->is_lock_owned((address)cur)) {
+ set_owner_from_BasicLock(THREAD, cur); // Convert from BasicLock* to Thread*.
_recursions = 0;
return true;
}
THROW_MSG_(vmSymbols::java_lang_IllegalMonitorStateException(),
"current thread is not owner", false);
@@ -1801,11 +1806,11 @@
// the spin without prejudice or apply a "penalty" to the
// spin count-down variable "ctr", reducing it by 100, say.
Thread * ox = (Thread *) _owner;
if (ox == NULL) {
- ox = (Thread*)Atomic::cmpxchg(Self, &_owner, (void*)NULL);
+ ox = (Thread*)try_set_owner_from(Self, NULL);
if (ox == NULL) {
// The CAS succeeded -- this thread acquired ownership
// Take care of some bookkeeping to exit spin state.
if (_succ == Self) {
_succ = NULL;
@@ -2154,5 +2159,91 @@
",recursions=" INTX_FORMAT ",owner=" INTPTR_FORMAT "}",
contentions(), waiters(), recursions(),
p2i(owner()));
}
void ObjectMonitor::print() const { print_on(tty); }
+
+// Print the ObjectMonitor like a debugger would:
+//
+// (ObjectMonitor) 0x00007fdfb6012e40 = {
+// _header = (_value = 1)
+// _object = 0x000000070ff45fd0
+// _allocation_state = Old
+// _pad_buf0 = {
+// [0] = '\0'
+// ...
+// [43] = '\0'
+// }
+// _owner = 0x0000000000000000
+// _previous_owner_tid = 0
+// _pad_buf1 = {
+// [0] = '\0'
+// ...
+// [47] = '\0'
+// }
+// _ref_count = 1
+// _pad_buf2 = {
+// [0] = '\0'
+// ...
+// [59] = '\0'
+// }
+// _next_om = 0x0000000000000000
+// _recursions = 0
+// _EntryList = 0x0000000000000000
+// _cxq = 0x0000000000000000
+// _succ = 0x0000000000000000
+// _Responsible = 0x0000000000000000
+// _Spinner = 0
+// _SpinDuration = 5000
+// _contentions = 0
+// _WaitSet = 0x0000700009756248
+// _waiters = 1
+// _WaitSetLock = 0
+// }
+//
+void ObjectMonitor::print_debug_style_on(outputStream* st) const {
+ st->print_cr("(ObjectMonitor *) " INTPTR_FORMAT " = {", p2i(this));
+ st->print_cr(" _header = " INTPTR_FORMAT, header().value());
+ st->print_cr(" _object = " INTPTR_FORMAT, p2i(_object));
+ st->print(" _allocation_state = ");
+ if (is_free()) {
+ st->print("Free");
+ } else if (is_old()) {
+ st->print("Old");
+ } else if (is_new()) {
+ st->print("New");
+ } else {
+ st->print("unknown=%d", _allocation_state);
+ }
+ st->cr();
+ st->print_cr(" _pad_buf0 = {");
+ st->print_cr(" [0] = '\\0'");
+ st->print_cr(" ...");
+ st->print_cr(" [%d] = '\\0'", (int)sizeof(_pad_buf0) - 1);
+ st->print_cr(" }");
+ st->print_cr(" _owner = " INTPTR_FORMAT, p2i(_owner));
+ st->print_cr(" _previous_owner_tid = " JLONG_FORMAT, _previous_owner_tid);
+ st->print_cr(" _pad_buf1 = {");
+ st->print_cr(" [0] = '\\0'");
+ st->print_cr(" ...");
+ st->print_cr(" [%d] = '\\0'", (int)sizeof(_pad_buf1) - 1);
+ st->print_cr(" }");
+ st->print_cr(" _ref_count = %d", ref_count());
+ st->print_cr(" _pad_buf2 = {");
+ st->print_cr(" [0] = '\\0'");
+ st->print_cr(" ...");
+ st->print_cr(" [%d] = '\\0'", (int)sizeof(_pad_buf1) - 1);
+ st->print_cr(" }");
+ st->print_cr(" _next_om = " INTPTR_FORMAT, p2i(_next_om));
+ st->print_cr(" _recursions = " INTX_FORMAT, _recursions);
+ st->print_cr(" _EntryList = " INTPTR_FORMAT, p2i(_EntryList));
+ st->print_cr(" _cxq = " INTPTR_FORMAT, p2i(_cxq));
+ st->print_cr(" _succ = " INTPTR_FORMAT, p2i(_succ));
+ st->print_cr(" _Responsible = " INTPTR_FORMAT, p2i(_Responsible));
+ st->print_cr(" _Spinner = %d", _Spinner);
+ st->print_cr(" _SpinDuration = %d", _SpinDuration);
+ st->print_cr(" _contentions = %d", _contentions);
+ st->print_cr(" _WaitSet = " INTPTR_FORMAT, p2i(_WaitSet));
+ st->print_cr(" _waiters = %d", _waiters);
+ st->print_cr(" _WaitSetLock = %d", _WaitSetLock);
+ st->print_cr("}");
+}
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