jdk8-mips64-public/hotspot: src/share/vm/prims/jvmtiRawMonitor.cpp@fa83ab460c54 (annotated)

src/share/vm/prims/jvmtiRawMonitor.cpp@fa83ab460c54 (annotated)

src/share/vm/prims/jvmtiRawMonitor.cpp

Fri, 22 Oct 2010 15:59:34 -0400

author: acorn
date: Fri, 22 Oct 2010 15:59:34 -0400
changeset 2233: fa83ab460c54
child 2314: f95d63e2154a
permissions: -rw-r--r--

6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp

 /*
  * Copyright (c) 2003, 2007, 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 "incls/_precompiled.incl"
 # include "incls/_jvmtiRawMonitor.cpp.incl"
 GrowableArray<JvmtiRawMonitor*> *JvmtiPendingMonitors::_monitors = new (ResourceObj::C_HEAP) 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), 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;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/prims/jvmtiRawMonitor.cpp@fa83ab460c54 (annotated)

src/share/vm/prims/jvmtiRawMonitor.cpp