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