| /* |
| * Copyright (c) 2003, 2012, 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. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "prims/jvmtiRawMonitor.hpp" |
| #include "runtime/interfaceSupport.hpp" |
| #include "runtime/orderAccess.inline.hpp" |
| #include "runtime/thread.inline.hpp" |
| |
| GrowableArray<JvmtiRawMonitor*> *JvmtiPendingMonitors::_monitors = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<JvmtiRawMonitor*>(1,true); |
| |
| void JvmtiPendingMonitors::transition_raw_monitors() { |
| assert((Threads::number_of_threads()==1), |
| "Java thread has not created yet or more than one java thread \ |
| is running. Raw monitor transition will not work"); |
| JavaThread *current_java_thread = JavaThread::current(); |
| assert(current_java_thread->thread_state() == _thread_in_vm, "Must be in vm"); |
| { |
| ThreadBlockInVM __tbivm(current_java_thread); |
| for(int i=0; i< count(); i++) { |
| JvmtiRawMonitor *rmonitor = monitors()->at(i); |
| int r = rmonitor->raw_enter(current_java_thread); |
| assert(r == ObjectMonitor::OM_OK, "raw_enter should have worked"); |
| } |
| } |
| // pending monitors are converted to real monitor so delete them all. |
| dispose(); |
| } |
| |
| // |
| // class JvmtiRawMonitor |
| // |
| |
| JvmtiRawMonitor::JvmtiRawMonitor(const char *name) { |
| #ifdef ASSERT |
| _name = strcpy(NEW_C_HEAP_ARRAY(char, strlen(name) + 1, mtInternal), name); |
| #else |
| _name = NULL; |
| #endif |
| _magic = JVMTI_RM_MAGIC; |
| } |
| |
| JvmtiRawMonitor::~JvmtiRawMonitor() { |
| #ifdef ASSERT |
| FreeHeap(_name); |
| #endif |
| _magic = 0; |
| } |
| |
| |
| bool |
| JvmtiRawMonitor::is_valid() { |
| int value = 0; |
| |
| // This object might not be a JvmtiRawMonitor so we can't assume |
| // the _magic field is properly aligned. Get the value in a safe |
| // way and then check against JVMTI_RM_MAGIC. |
| |
| switch (sizeof(_magic)) { |
| case 2: |
| value = Bytes::get_native_u2((address)&_magic); |
| break; |
| |
| case 4: |
| value = Bytes::get_native_u4((address)&_magic); |
| break; |
| |
| case 8: |
| value = Bytes::get_native_u8((address)&_magic); |
| break; |
| |
| default: |
| guarantee(false, "_magic field is an unexpected size"); |
| } |
| |
| return value == JVMTI_RM_MAGIC; |
| } |
| |
| // ------------------------------------------------------------------------- |
| // The raw monitor subsystem is entirely distinct from normal |
| // java-synchronization or jni-synchronization. raw monitors are not |
| // associated with objects. They can be implemented in any manner |
| // that makes sense. The original implementors decided to piggy-back |
| // the raw-monitor implementation on the existing Java objectMonitor mechanism. |
| // This flaw needs to fixed. We should reimplement raw monitors as sui-generis. |
| // Specifically, we should not implement raw monitors via java monitors. |
| // Time permitting, we should disentangle and deconvolve the two implementations |
| // and move the resulting raw monitor implementation over to the JVMTI directories. |
| // Ideally, the raw monitor implementation would be built on top of |
| // park-unpark and nothing else. |
| // |
| // raw monitors are used mainly by JVMTI |
| // The raw monitor implementation borrows the ObjectMonitor structure, |
| // but the operators are degenerate and extremely simple. |
| // |
| // Mixed use of a single objectMonitor instance -- as both a raw monitor |
| // and a normal java monitor -- is not permissible. |
| // |
| // Note that we use the single RawMonitor_lock to protect queue operations for |
| // _all_ raw monitors. This is a scalability impediment, but since raw monitor usage |
| // is deprecated and rare, this is not of concern. The RawMonitor_lock can not |
| // be held indefinitely. The critical sections must be short and bounded. |
| // |
| // ------------------------------------------------------------------------- |
| |
| int JvmtiRawMonitor::SimpleEnter (Thread * Self) { |
| for (;;) { |
| if (Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) { |
| return OS_OK ; |
| } |
| |
| ObjectWaiter Node (Self) ; |
| Self->_ParkEvent->reset() ; // strictly optional |
| Node.TState = ObjectWaiter::TS_ENTER ; |
| |
| RawMonitor_lock->lock_without_safepoint_check() ; |
| Node._next = _EntryList ; |
| _EntryList = &Node ; |
| OrderAccess::fence() ; |
| if (_owner == NULL && Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) { |
| _EntryList = Node._next ; |
| RawMonitor_lock->unlock() ; |
| return OS_OK ; |
| } |
| RawMonitor_lock->unlock() ; |
| while (Node.TState == ObjectWaiter::TS_ENTER) { |
| Self->_ParkEvent->park() ; |
| } |
| } |
| } |
| |
| int JvmtiRawMonitor::SimpleExit (Thread * Self) { |
| guarantee (_owner == Self, "invariant") ; |
| OrderAccess::release_store_ptr (&_owner, NULL) ; |
| OrderAccess::fence() ; |
| if (_EntryList == NULL) return OS_OK ; |
| ObjectWaiter * w ; |
| |
| RawMonitor_lock->lock_without_safepoint_check() ; |
| w = _EntryList ; |
| if (w != NULL) { |
| _EntryList = w->_next ; |
| } |
| RawMonitor_lock->unlock() ; |
| if (w != NULL) { |
| guarantee (w ->TState == ObjectWaiter::TS_ENTER, "invariant") ; |
| ParkEvent * ev = w->_event ; |
| w->TState = ObjectWaiter::TS_RUN ; |
| OrderAccess::fence() ; |
| ev->unpark() ; |
| } |
| return OS_OK ; |
| } |
| |
| int JvmtiRawMonitor::SimpleWait (Thread * Self, jlong millis) { |
| guarantee (_owner == Self , "invariant") ; |
| guarantee (_recursions == 0, "invariant") ; |
| |
| ObjectWaiter Node (Self) ; |
| Node._notified = 0 ; |
| Node.TState = ObjectWaiter::TS_WAIT ; |
| |
| RawMonitor_lock->lock_without_safepoint_check() ; |
| Node._next = _WaitSet ; |
| _WaitSet = &Node ; |
| RawMonitor_lock->unlock() ; |
| |
| SimpleExit (Self) ; |
| guarantee (_owner != Self, "invariant") ; |
| |
| int ret = OS_OK ; |
| if (millis <= 0) { |
| Self->_ParkEvent->park(); |
| } else { |
| ret = Self->_ParkEvent->park(millis); |
| } |
| |
| // If thread still resides on the waitset then unlink it. |
| // Double-checked locking -- the usage is safe in this context |
| // as we TState is volatile and the lock-unlock operators are |
| // serializing (barrier-equivalent). |
| |
| if (Node.TState == ObjectWaiter::TS_WAIT) { |
| RawMonitor_lock->lock_without_safepoint_check() ; |
| if (Node.TState == ObjectWaiter::TS_WAIT) { |
| // Simple O(n) unlink, but performance isn't critical here. |
| ObjectWaiter * p ; |
| ObjectWaiter * q = NULL ; |
| for (p = _WaitSet ; p != &Node; p = p->_next) { |
| q = p ; |
| } |
| guarantee (p == &Node, "invariant") ; |
| if (q == NULL) { |
| guarantee (p == _WaitSet, "invariant") ; |
| _WaitSet = p->_next ; |
| } else { |
| guarantee (p == q->_next, "invariant") ; |
| q->_next = p->_next ; |
| } |
| Node.TState = ObjectWaiter::TS_RUN ; |
| } |
| RawMonitor_lock->unlock() ; |
| } |
| |
| guarantee (Node.TState == ObjectWaiter::TS_RUN, "invariant") ; |
| SimpleEnter (Self) ; |
| |
| guarantee (_owner == Self, "invariant") ; |
| guarantee (_recursions == 0, "invariant") ; |
| return ret ; |
| } |
| |
| int JvmtiRawMonitor::SimpleNotify (Thread * Self, bool All) { |
| guarantee (_owner == Self, "invariant") ; |
| if (_WaitSet == NULL) return OS_OK ; |
| |
| // We have two options: |
| // A. Transfer the threads from the WaitSet to the EntryList |
| // B. Remove the thread from the WaitSet and unpark() it. |
| // |
| // We use (B), which is crude and results in lots of futile |
| // context switching. In particular (B) induces lots of contention. |
| |
| ParkEvent * ev = NULL ; // consider using a small auto array ... |
| RawMonitor_lock->lock_without_safepoint_check() ; |
| for (;;) { |
| ObjectWaiter * w = _WaitSet ; |
| if (w == NULL) break ; |
| _WaitSet = w->_next ; |
| if (ev != NULL) { ev->unpark(); ev = NULL; } |
| ev = w->_event ; |
| OrderAccess::loadstore() ; |
| w->TState = ObjectWaiter::TS_RUN ; |
| OrderAccess::storeload(); |
| if (!All) break ; |
| } |
| RawMonitor_lock->unlock() ; |
| if (ev != NULL) ev->unpark(); |
| return OS_OK ; |
| } |
| |
| // Any JavaThread will enter here with state _thread_blocked |
| int JvmtiRawMonitor::raw_enter(TRAPS) { |
| TEVENT (raw_enter) ; |
| void * Contended ; |
| |
| // don't enter raw monitor if thread is being externally suspended, it will |
| // surprise the suspender if a "suspended" thread can still enter monitor |
| JavaThread * jt = (JavaThread *)THREAD; |
| if (THREAD->is_Java_thread()) { |
| jt->SR_lock()->lock_without_safepoint_check(); |
| while (jt->is_external_suspend()) { |
| jt->SR_lock()->unlock(); |
| jt->java_suspend_self(); |
| jt->SR_lock()->lock_without_safepoint_check(); |
| } |
| // guarded by SR_lock to avoid racing with new external suspend requests. |
| Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ; |
| jt->SR_lock()->unlock(); |
| } else { |
| Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ; |
| } |
| |
| if (Contended == THREAD) { |
| _recursions ++ ; |
| return OM_OK ; |
| } |
| |
| if (Contended == NULL) { |
| guarantee (_owner == THREAD, "invariant") ; |
| guarantee (_recursions == 0, "invariant") ; |
| return OM_OK ; |
| } |
| |
| THREAD->set_current_pending_monitor(this); |
| |
| if (!THREAD->is_Java_thread()) { |
| // No other non-Java threads besides VM thread would acquire |
| // a raw monitor. |
| assert(THREAD->is_VM_thread(), "must be VM thread"); |
| SimpleEnter (THREAD) ; |
| } else { |
| guarantee (jt->thread_state() == _thread_blocked, "invariant") ; |
| for (;;) { |
| jt->set_suspend_equivalent(); |
| // cleared by handle_special_suspend_equivalent_condition() or |
| // java_suspend_self() |
| SimpleEnter (THREAD) ; |
| |
| // were we externally suspended while we were waiting? |
| if (!jt->handle_special_suspend_equivalent_condition()) break ; |
| |
| // This thread was externally suspended |
| // |
| // This logic isn't needed for JVMTI raw monitors, |
| // but doesn't hurt just in case the suspend rules change. This |
| // logic is needed for the JvmtiRawMonitor.wait() reentry phase. |
| // We have reentered the contended monitor, but while we were |
| // waiting another thread suspended us. We don't want to reenter |
| // the monitor while suspended because that would surprise the |
| // thread that suspended us. |
| // |
| // Drop the lock - |
| SimpleExit (THREAD) ; |
| |
| jt->java_suspend_self(); |
| } |
| |
| assert(_owner == THREAD, "Fatal error with monitor owner!"); |
| assert(_recursions == 0, "Fatal error with monitor recursions!"); |
| } |
| |
| THREAD->set_current_pending_monitor(NULL); |
| guarantee (_recursions == 0, "invariant") ; |
| return OM_OK; |
| } |
| |
| // Used mainly for JVMTI raw monitor implementation |
| // Also used for JvmtiRawMonitor::wait(). |
| int JvmtiRawMonitor::raw_exit(TRAPS) { |
| TEVENT (raw_exit) ; |
| if (THREAD != _owner) { |
| return OM_ILLEGAL_MONITOR_STATE; |
| } |
| if (_recursions > 0) { |
| --_recursions ; |
| return OM_OK ; |
| } |
| |
| void * List = _EntryList ; |
| SimpleExit (THREAD) ; |
| |
| return OM_OK; |
| } |
| |
| // Used for JVMTI raw monitor implementation. |
| // All JavaThreads will enter here with state _thread_blocked |
| |
| int JvmtiRawMonitor::raw_wait(jlong millis, bool interruptible, TRAPS) { |
| TEVENT (raw_wait) ; |
| if (THREAD != _owner) { |
| return OM_ILLEGAL_MONITOR_STATE; |
| } |
| |
| // To avoid spurious wakeups we reset the parkevent -- This is strictly optional. |
| // The caller must be able to tolerate spurious returns from raw_wait(). |
| THREAD->_ParkEvent->reset() ; |
| OrderAccess::fence() ; |
| |
| // check interrupt event |
| if (interruptible && Thread::is_interrupted(THREAD, true)) { |
| return OM_INTERRUPTED; |
| } |
| |
| intptr_t save = _recursions ; |
| _recursions = 0 ; |
| _waiters ++ ; |
| if (THREAD->is_Java_thread()) { |
| guarantee (((JavaThread *) THREAD)->thread_state() == _thread_blocked, "invariant") ; |
| ((JavaThread *)THREAD)->set_suspend_equivalent(); |
| } |
| int rv = SimpleWait (THREAD, millis) ; |
| _recursions = save ; |
| _waiters -- ; |
| |
| guarantee (THREAD == _owner, "invariant") ; |
| if (THREAD->is_Java_thread()) { |
| JavaThread * jSelf = (JavaThread *) THREAD ; |
| for (;;) { |
| if (!jSelf->handle_special_suspend_equivalent_condition()) break ; |
| SimpleExit (THREAD) ; |
| jSelf->java_suspend_self(); |
| SimpleEnter (THREAD) ; |
| jSelf->set_suspend_equivalent() ; |
| } |
| } |
| guarantee (THREAD == _owner, "invariant") ; |
| |
| if (interruptible && Thread::is_interrupted(THREAD, true)) { |
| return OM_INTERRUPTED; |
| } |
| return OM_OK ; |
| } |
| |
| int JvmtiRawMonitor::raw_notify(TRAPS) { |
| TEVENT (raw_notify) ; |
| if (THREAD != _owner) { |
| return OM_ILLEGAL_MONITOR_STATE; |
| } |
| SimpleNotify (THREAD, false) ; |
| return OM_OK; |
| } |
| |
| int JvmtiRawMonitor::raw_notifyAll(TRAPS) { |
| TEVENT (raw_notifyAll) ; |
| if (THREAD != _owner) { |
| return OM_ILLEGAL_MONITOR_STATE; |
| } |
| SimpleNotify (THREAD, true) ; |
| return OM_OK; |
| } |
| |