1 /*
   2  * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_RUNTIME_SYNCHRONIZER_HPP
  26 #define SHARE_VM_RUNTIME_SYNCHRONIZER_HPP
  27 
  28 #include "memory/padded.hpp"
  29 #include "oops/markOop.hpp"
  30 #include "runtime/basicLock.hpp"
  31 #include "runtime/handles.hpp"
  32 #include "runtime/perfData.hpp"
  33 
  34 class ObjectMonitor;
  35 class ThreadsList;
  36 
  37 struct DeflateMonitorCounters {
  38   int nInuse;          // currently associated with objects
  39   int nInCirculation;  // extant
  40   int nScavenged;      // reclaimed
  41 };
  42 
  43 class ObjectSynchronizer : AllStatic {
  44   friend class VMStructs;
  45  public:
  46   typedef enum {
  47     owner_self,
  48     owner_none,
  49     owner_other
  50   } LockOwnership;
  51 
  52   typedef enum {
  53     inflate_cause_vm_internal = 0,
  54     inflate_cause_monitor_enter = 1,
  55     inflate_cause_wait = 2,
  56     inflate_cause_notify = 3,
  57     inflate_cause_hash_code = 4,
  58     inflate_cause_jni_enter = 5,
  59     inflate_cause_jni_exit = 6,
  60     inflate_cause_nof = 7 // Number of causes
  61   } InflateCause;
  62 
  63   // exit must be implemented non-blocking, since the compiler cannot easily handle
  64   // deoptimization at monitor exit. Hence, it does not take a Handle argument.
  65 
  66   // This is full version of monitor enter and exit. I choose not
  67   // to use enter() and exit() in order to make sure user be ware
  68   // of the performance and semantics difference. They are normally
  69   // used by ObjectLocker etc. The interpreter and compiler use
  70   // assembly copies of these routines. Please keep them synchronized.
  71   //
  72   // attempt_rebias flag is used by UseBiasedLocking implementation
  73   static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
  74                          TRAPS);
  75   static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);
  76 
  77   // WARNING: They are ONLY used to handle the slow cases. They should
  78   // only be used when the fast cases failed. Use of these functions
  79   // without previous fast case check may cause fatal error.
  80   static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
  81   static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);
  82 
  83   // Used only to handle jni locks or other unmatched monitor enter/exit
  84   // Internally they will use heavy weight monitor.
  85   static void jni_enter(Handle obj, TRAPS);
  86   static void jni_exit(oop obj, Thread* THREAD);
  87 
  88   // Handle all interpreter, compiler and jni cases
  89   static int  wait(Handle obj, jlong millis, TRAPS);
  90   static void notify(Handle obj, TRAPS);
  91   static void notifyall(Handle obj, TRAPS);
  92 
  93   static bool quick_notify(oopDesc* obj, Thread* Self, bool All);
  94   static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);
  95 
  96   // Special internal-use-only method for use by JVM infrastructure
  97   // that needs to wait() on a java-level object but that can't risk
  98   // throwing unexpected InterruptedExecutionExceptions.
  99   static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);
 100 
 101   // used by classloading to free classloader object lock,
 102   // wait on an internal lock, and reclaim original lock
 103   // with original recursion count
 104   static intptr_t complete_exit(Handle obj, TRAPS);
 105   static void reenter (Handle obj, intptr_t recursion, TRAPS);
 106 
 107   // thread-specific and global objectMonitor free list accessors
 108   static void verifyInUse(Thread * Self);
 109   static ObjectMonitor * omAlloc(Thread * Self);
 110   static void omRelease(Thread * Self, ObjectMonitor * m,
 111                         bool FromPerThreadAlloc);
 112   static void omFlush(Thread * Self);
 113 
 114   // Inflate light weight monitor to heavy weight monitor
 115   static ObjectMonitor* inflate(Thread * Self, oop obj, const InflateCause cause);
 116   // This version is only for internal use
 117   static ObjectMonitor* inflate_helper(oop obj);
 118   static const char* inflate_cause_name(const InflateCause cause);
 119 
 120   // Returns the identity hash value for an oop
 121   // NOTE: It may cause monitor inflation
 122   static intptr_t identity_hash_value_for(Handle obj);
 123   static intptr_t FastHashCode(Thread * Self, oop obj);
 124 
 125   // java.lang.Thread support
 126   static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
 127   static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);
 128 
 129   static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
 130 
 131   // JNI detach support
 132   static void release_monitors_owned_by_thread(TRAPS);
 133   static void monitors_iterate(MonitorClosure* m);
 134 
 135   // GC: we current use aggressive monitor deflation policy
 136   // Basically we deflate all monitors that are not busy.
 137   // An adaptive profile-based deflation policy could be used if needed
 138   static void deflate_idle_monitors(DeflateMonitorCounters* counters);
 139   static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
 140   static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
 141   static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
 142 
 143   // For a given monitor list: global or per-thread, deflate idle monitors
 144   static int deflate_monitor_list(ObjectMonitor** listheadp,
 145                                   ObjectMonitor** freeHeadp,
 146                                   ObjectMonitor** freeTailp);
 147   static bool deflate_monitor(ObjectMonitor* mid, oop obj,
 148                               ObjectMonitor** freeHeadp,
 149                               ObjectMonitor** freeTailp);
 150   static bool is_cleanup_needed();
 151   static void oops_do(OopClosure* f);
 152   // Process oops in thread local used monitors
 153   static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
 154 
 155   // debugging
 156   static void sanity_checks(const bool verbose,
 157                             const unsigned int cache_line_size,
 158                             int *error_cnt_ptr, int *warning_cnt_ptr);
 159   static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
 160 
 161  private:
 162   enum { _BLOCKSIZE = 128 };
 163   // global list of blocks of monitors
 164   static PaddedEnd<ObjectMonitor> * volatile gBlockList;
 165   // global monitor free list
 166   static ObjectMonitor * volatile gFreeList;
 167   // global monitor in-use list, for moribund threads,
 168   // monitors they inflated need to be scanned for deflation
 169   static ObjectMonitor * volatile gOmInUseList;
 170   // count of entries in gOmInUseList
 171   static int gOmInUseCount;
 172 
 173   // Process oops in all monitors
 174   static void global_oops_do(OopClosure* f);
 175   // Process oops in all global used monitors (i.e. moribund thread's monitors)
 176   static void global_used_oops_do(OopClosure* f);
 177   // Process oops in monitors on the given list
 178   static void list_oops_do(ObjectMonitor* list, OopClosure* f);
 179 
 180 };
 181 
 182 // ObjectLocker enforced balanced locking and can never thrown an
 183 // IllegalMonitorStateException. However, a pending exception may
 184 // have to pass through, and we must also be able to deal with
 185 // asynchronous exceptions. The caller is responsible for checking
 186 // the threads pending exception if needed.
 187 // doLock was added to support classloading with UnsyncloadClass which
 188 // requires flag based choice of locking the classloader lock.
 189 class ObjectLocker : public StackObj {
 190  private:
 191   Thread*   _thread;
 192   Handle    _obj;
 193   BasicLock _lock;
 194   bool      _dolock;   // default true
 195  public:
 196   ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
 197   ~ObjectLocker();
 198 
 199   // Monitor behavior
 200   void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
 201   void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
 202   void waitUninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); }
 203   // complete_exit gives up lock completely, returning recursion count
 204   // reenter reclaims lock with original recursion count
 205   intptr_t complete_exit(TRAPS)  { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
 206   void reenter(intptr_t recursion, TRAPS)  { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
 207 };
 208 
 209 #endif // SHARE_VM_RUNTIME_SYNCHRONIZER_HPP