1 /*
   2  * Copyright (c) 1998, 2019, 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_RUNTIME_SYNCHRONIZER_HPP
  26 #define SHARE_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 (global and per-thread)
  41   int perThreadScavenged;  // per-thread scavenge total
  42   double perThreadTimes;   // per-thread scavenge times
  43 };
  44 
  45 class ObjectSynchronizer : AllStatic {
  46   friend class VMStructs;
  47  public:
  48   typedef enum {
  49     owner_self,
  50     owner_none,
  51     owner_other
  52   } LockOwnership;
  53 
  54   typedef enum {
  55     inflate_cause_vm_internal = 0,
  56     inflate_cause_monitor_enter = 1,
  57     inflate_cause_wait = 2,
  58     inflate_cause_notify = 3,
  59     inflate_cause_hash_code = 4,
  60     inflate_cause_jni_enter = 5,
  61     inflate_cause_jni_exit = 6,
  62     inflate_cause_nof = 7 // Number of causes
  63   } InflateCause;
  64 
  65   // exit must be implemented non-blocking, since the compiler cannot easily handle
  66   // deoptimization at monitor exit. Hence, it does not take a Handle argument.
  67 
  68   // This is full version of monitor enter and exit. I choose not
  69   // to use enter() and exit() in order to make sure user be ware
  70   // of the performance and semantics difference. They are normally
  71   // used by ObjectLocker etc. The interpreter and compiler use
  72   // assembly copies of these routines. Please keep them synchronized.
  73   //
  74   // attempt_rebias flag is used by UseBiasedLocking implementation
  75   static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
  76                          TRAPS);
  77   static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);
  78 
  79   // WARNING: They are ONLY used to handle the slow cases. They should
  80   // only be used when the fast cases failed. Use of these functions
  81   // without previous fast case check may cause fatal error.
  82   static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
  83   static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);
  84 
  85   // Used only to handle jni locks or other unmatched monitor enter/exit
  86   // Internally they will use heavy weight monitor.
  87   static void jni_enter(Handle obj, TRAPS);
  88   static void jni_exit(oop obj, Thread* THREAD);
  89 
  90   // Handle all interpreter, compiler and jni cases
  91   static int  wait(Handle obj, jlong millis, TRAPS);
  92   static void notify(Handle obj, TRAPS);
  93   static void notifyall(Handle obj, TRAPS);
  94 
  95   static bool quick_notify(oopDesc* obj, Thread* Self, bool All);
  96   static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);
  97 
  98   // Special internal-use-only method for use by JVM infrastructure
  99   // that needs to wait() on a java-level object but that can't risk
 100   // throwing unexpected InterruptedExecutionExceptions.
 101   static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);
 102 
 103   // used by classloading to free classloader object lock,
 104   // wait on an internal lock, and reclaim original lock
 105   // with original recursion count
 106   static intptr_t complete_exit(Handle obj, TRAPS);
 107   static void reenter (Handle obj, intptr_t recursion, TRAPS);
 108 
 109   // thread-specific and global objectMonitor free list accessors
 110   static ObjectMonitor * omAlloc(Thread * Self);
 111   static void omRelease(Thread * Self, ObjectMonitor * m,
 112                         bool FromPerThreadAlloc);
 113   static void omFlush(Thread * Self);
 114 
 115   // Inflate light weight monitor to heavy weight monitor
 116   static ObjectMonitor* inflate(Thread * Self, oop obj, const InflateCause cause);
 117   // This version is only for internal use
 118   static void inflate_helper(oop obj);
 119   static const char* inflate_cause_name(const InflateCause cause);
 120 
 121   // Returns the identity hash value for an oop
 122   // NOTE: It may cause monitor inflation
 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 audit_and_print_stats(bool on_exit);
 157   static void chk_free_entry(JavaThread * jt, ObjectMonitor * n,
 158                              outputStream * out, int *error_cnt_p);
 159   static void chk_global_free_list_and_count(outputStream * out,
 160                                              int *error_cnt_p);
 161   static void chk_global_in_use_list_and_count(outputStream * out,
 162                                                int *error_cnt_p);
 163   static void chk_in_use_entry(JavaThread * jt, ObjectMonitor * n,
 164                                outputStream * out, int *error_cnt_p);
 165   static void chk_per_thread_in_use_list_and_count(JavaThread *jt,
 166                                                    outputStream * out,
 167                                                    int *error_cnt_p);
 168   static void chk_per_thread_free_list_and_count(JavaThread *jt,
 169                                                  outputStream * out,
 170                                                  int *error_cnt_p);
 171   static void log_in_use_monitor_details(outputStream * out, bool on_exit);
 172   static int  log_monitor_list_counts(outputStream * out);
 173   static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
 174 
 175  private:
 176   friend class SynchronizerTest;
 177 
 178   enum { _BLOCKSIZE = 128 };
 179   // global list of blocks of monitors
 180   static PaddedEnd<ObjectMonitor> * volatile gBlockList;
 181   // global monitor free list
 182   static ObjectMonitor * volatile gFreeList;
 183   // global monitor in-use list, for moribund threads,
 184   // monitors they inflated need to be scanned for deflation
 185   static ObjectMonitor * volatile gOmInUseList;
 186   // count of entries in gOmInUseList
 187   static int gOmInUseCount;
 188 
 189   // Process oops in all global used monitors (i.e. moribund thread's monitors)
 190   static void global_used_oops_do(OopClosure* f);
 191   // Process oops in monitors on the given list
 192   static void list_oops_do(ObjectMonitor* list, OopClosure* f);
 193 
 194   // Support for SynchronizerTest access to GVars fields:
 195   static u_char* get_gvars_addr();
 196   static u_char* get_gvars_hcSequence_addr();
 197   static size_t get_gvars_size();
 198   static u_char* get_gvars_stwRandom_addr();
 199 };
 200 
 201 // ObjectLocker enforces balanced locking and can never throw an
 202 // IllegalMonitorStateException. However, a pending exception may
 203 // have to pass through, and we must also be able to deal with
 204 // asynchronous exceptions. The caller is responsible for checking
 205 // the thread's pending exception if needed.
 206 class ObjectLocker : public StackObj {
 207  private:
 208   Thread*   _thread;
 209   Handle    _obj;
 210   BasicLock _lock;
 211   bool      _dolock;   // default true
 212  public:
 213   ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
 214   ~ObjectLocker();
 215 
 216   // Monitor behavior
 217   void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
 218   void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
 219   void waitUninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); }
 220   // complete_exit gives up lock completely, returning recursion count
 221   // reenter reclaims lock with original recursion count
 222   intptr_t complete_exit(TRAPS)  { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
 223   void reenter(intptr_t recursion, TRAPS)  { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
 224 };
 225 
 226 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP