truffle: src/share/vm/runtime/objectMonitor.cpp comparison

comparison src/share/vm/runtime/objectMonitor.cpp @ 14518:d8041d695d19

Merged with jdk9/dev/hotspot changeset 3812c088b945

author	twisti
date	Tue, 11 Mar 2014 18:45:59 -0700
parents	28f281e8de1d
children	4ca6dc0799b6

comparison

equal deleted inserted replaced

-:f97c5ec83832
+:d8041d695d19
 /*
-* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
+* Copyright (c) 1998, 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 #endif
 #ifdef TARGET_OS_FAMILY_bsd
 # include "os_bsd.inline.hpp"
 #endif
-#if defined(__GNUC__) && !defined(IA64)
+#if defined(__GNUC__) && !defined(IA64) && !defined(PPC64)
 // Need to inhibit inlining for older versions of GCC to avoid build-time failures
 #define ATTR __attribute__((noinline))
 #else
 #define ATTR
 #endif
 if (klassname != NULL) {                                                 \
 bytes = (char*)klassname->bytes();                                     \
 len = klassname->utf8_length();                                        \
 }
-#ifndef USDT2
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__notify,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__notifyAll,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__enter,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__entered,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__exit,
-jlong, uintptr_t, char*, int);
-#define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis)       \
-{                                                                        \
-if (DTraceMonitorProbes) {                                            \
-DTRACE_MONITOR_PROBE_COMMON(obj, thread);                       \
-HS_DTRACE_PROBE5(hotspot, monitor__wait, jtid,                       \
-(monitor), bytes, len, (millis));                   \
-}                                                                      \
-}
-#define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread)             \
-{                                                                        \
-if (DTraceMonitorProbes) {                                            \
-DTRACE_MONITOR_PROBE_COMMON(obj, thread);                       \
-HS_DTRACE_PROBE4(hotspot, monitor__##probe, jtid,                    \
-(uintptr_t)(monitor), bytes, len);                  \
-}                                                                      \
-}
-#else /* USDT2 */
 #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis)            \
 {                                                                        \
 if (DTraceMonitorProbes) {                                            \
 DTRACE_MONITOR_PROBE_COMMON(obj, thread);                            \
 HOTSPOT_MONITOR_WAIT(jtid,                                           \
 HOTSPOT_MONITOR_##probe(jtid,                                               \
 (uintptr_t)(monitor), bytes, len);                  \
 }                                                                      \
 }
-#endif /* USDT2 */
 #else //  ndef DTRACE_ENABLED
 #define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon)    {;}
 #define DTRACE_MONITOR_PROBE(probe, obj, thread, mon)          {;}
 //   More precisely, the CAS-based "push" onto cxq is ABA-oblivious.
 //
 // * Taken together, the cxq and the EntryList constitute or form a
 //   single logical queue of threads stalled trying to acquire the lock.
 //   We use two distinct lists to improve the odds of a constant-time
-//   dequeue operation after acquisition (in the ::enter() epilog) and
+//   dequeue operation after acquisition (in the ::enter() epilogue) and
 //   to reduce heat on the list ends.  (c.f. Michael Scott's "2Q" algorithm).
 //   A key desideratum is to minimize queue & monitor metadata manipulation
 //   that occurs while holding the monitor lock -- that is, we want to
 //   minimize monitor lock holds times.  Note that even a small amount of
 //   fixed spinning will greatly reduce the # of enqueue-dequeue operations
 JavaThreadBlockedOnMonitorEnterState jtbmes(jt, this);
 DTRACE_MONITOR_PROBE(contended__enter, this, object(), jt);
 if (JvmtiExport::should_post_monitor_contended_enter()) {
 JvmtiExport::post_monitor_contended_enter(jt, this);
+// The current thread does not yet own the monitor and does not
+// yet appear on any queues that would get it made the successor.
+// This means that the JVMTI_EVENT_MONITOR_CONTENDED_ENTER event
+// handler cannot accidentally consume an unpark() meant for the
+// ParkEvent associated with this ObjectMonitor.
 }
 OSThreadContendState osts(Self->osthread());
 ThreadBlockInVM tbivm(jt);
 // spinning we could increment JVMStat counters, etc.
 DTRACE_MONITOR_PROBE(contended__entered, this, object(), jt);
 if (JvmtiExport::should_post_monitor_contended_entered()) {
 JvmtiExport::post_monitor_contended_entered(jt, this);
+// The current thread already owns the monitor and is not going to
+// call park() for the remainder of the monitor enter protocol. So
+// it doesn't matter if the JVMTI_EVENT_MONITOR_CONTENDED_ENTERED
+// event handler consumed an unpark() issued by the thread that
+// just exited the monitor.
 }
 if (event.should_commit()) {
 event.set_klass(((oop)this->object())->klass());
 event.set_previousOwner((TYPE_JAVALANGTHREAD)_previous_owner_tid);
 // by LDing cxq|EntryList.  Newly arrived threads -- that is, threads
 // that arrive on cxq after the ST:MEMBAR, above -- will set Responsible
 // non-null and elect a new "Responsible" timer thread.
 //
 // This thread executes:
-//    ST Responsible=null; MEMBAR    (in enter epilog - here)
+//    ST Responsible=null; MEMBAR    (in enter epilogue - here)
 //    LD cxq|EntryList               (in subsequent exit)
 //
 // Entering threads in the slow/contended path execute:
 //    ST cxq=nonnull; MEMBAR; LD Responsible (in enter prolog)
 //    The (ST cxq; MEMBAR) is accomplished with CAS().
 // post monitor waited event.  Note that this is past-tense, we are done waiting.
 if (JvmtiExport::should_post_monitor_waited()) {
 // Note: 'false' parameter is passed here because the
 // wait was not timed out due to thread interrupt.
 JvmtiExport::post_monitor_waited(jt, this, false);
+// In this short circuit of the monitor wait protocol, the
+// current thread never drops ownership of the monitor and
+// never gets added to the wait queue so the current thread
+// cannot be made the successor. This means that the
+// JVMTI_EVENT_MONITOR_WAITED event handler cannot accidentally
+// consume an unpark() meant for the ParkEvent associated with
+// this ObjectMonitor.
 }
 if (event.should_commit()) {
 post_monitor_wait_event(&event, 0, millis, false);
 }
 TEVENT (Wait - Throw IEX) ;
 intptr_t save = _recursions; // record the old recursion count
 _waiters++;                  // increment the number of waiters
 _recursions = 0;             // set the recursion level to be 1
 exit (true, Self) ;                    // exit the monitor
 guarantee (_owner != Self, "invariant") ;
-// As soon as the ObjectMonitor's ownership is dropped in the exit()
-// call above, another thread can enter() the ObjectMonitor, do the
-// notify(), and exit() the ObjectMonitor. If the other thread's
-// exit() call chooses this thread as the successor and the unpark()
-// call happens to occur while this thread is posting a
-// MONITOR_CONTENDED_EXIT event, then we run the risk of the event
-// handler using RawMonitors and consuming the unpark().
-//
-// To avoid the problem, we re-post the event. This does no harm
-// even if the original unpark() was not consumed because we are the
-// chosen successor for this monitor.
-if (node._notified != 0 && _succ == Self) {
-node._event->unpark();
-}
 // The thread is on the WaitSet list - now park() it.
 // On MP systems it's conceivable that a brief spin before we park
 // could be profitable.
 //
 // (Don't cache naked oops over safepoints, of course).
 // post monitor waited event. Note that this is past-tense, we are done waiting.
 if (JvmtiExport::should_post_monitor_waited()) {
 JvmtiExport::post_monitor_waited(jt, this, ret == OS_TIMEOUT);
+if (node._notified != 0 && _succ == Self) {
+// In this part of the monitor wait-notify-reenter protocol it
+// is possible (and normal) for another thread to do a fastpath
+// monitor enter-exit while this thread is still trying to get
+// to the reenter portion of the protocol.
+//
+// The ObjectMonitor was notified and the current thread is
+// the successor which also means that an unpark() has already
+// been done. The JVMTI_EVENT_MONITOR_WAITED event handler can
+// consume the unpark() that was done when the successor was
+// set because the same ParkEvent is shared between Java
+// monitors and JVM/TI RawMonitors (for now).
+//
+// We redo the unpark() to ensure forward progress, i.e., we
+// don't want all pending threads hanging (parked) with none
+// entering the unlocked monitor.
+node._event->unpark();
+}
 }
 if (event.should_commit()) {
 post_monitor_wait_event(&event, node._notifier_tid, millis, ret == OS_TIMEOUT);
 }
 if (MaxSpin >= 0) {
 if (_Spinner > MaxSpin) {
 TEVENT (Spin abort -- too many spinners) ;
 return 0 ;
 }
-// Slighty racy, but benign ...
+// Slightly racy, but benign ...
 Adjust (&_Spinner, 1) ;
 }
 // We're good to spin ... spin ingress.
 // CONSIDER: use Prefetch::write() to avoid RTS->RTO upgrades

Mercurial > hg > truffle

comparison src/share/vm/runtime/objectMonitor.cpp @ 14518:d8041d695d19