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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    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

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_RUNTIME_SYNCHRONIZER_HPP

    26 #define SHARE_VM_RUNTIME_SYNCHRONIZER_HPP

    27 

    28 #include "oops/markOop.hpp"

    29 #include "runtime/basicLock.hpp"

    30 #include "runtime/handles.hpp"

    31 #include "runtime/perfData.hpp"

    32 

    33 class ObjectMonitor;

    34 

    35 struct DeflateMonitorCounters {

    36   int nInuse;          // currently associated with objects

    37   int nInCirculation;  // extant

    38   int nScavenged;      // reclaimed

    39 };

    40 

    41 class ObjectSynchronizer : AllStatic {

    42   friend class VMStructs;

    43  public:

    44   typedef enum {

    45     owner_self,

    46     owner_none,

    47     owner_other

    48   } LockOwnership;

    49 

    50   typedef enum {

    51     inflate_cause_vm_internal = 0,

    52     inflate_cause_monitor_enter = 1,

    53     inflate_cause_wait = 2,

    54     inflate_cause_notify = 3,

    55     inflate_cause_hash_code = 4,

    56     inflate_cause_jni_enter = 5,

    57     inflate_cause_jni_exit = 6,

    58     inflate_cause_nof = 7 // Number of causes

    59   } InflateCause;

    60 

    61   // exit must be implemented non-blocking, since the compiler cannot easily handle

    62   // deoptimization at monitor exit. Hence, it does not take a Handle argument.

    63 

    64   // This is full version of monitor enter and exit. I choose not

    65   // to use enter() and exit() in order to make sure user be ware

    66   // of the performance and semantics difference. They are normally

    67   // used by ObjectLocker etc. The interpreter and compiler use

    68   // assembly copies of these routines. Please keep them synchronized.

    69   //

    70   // attempt_rebias flag is used by UseBiasedLocking implementation

    71   static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,

    72                          TRAPS);

    73   static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);

    74 

    75   // WARNING: They are ONLY used to handle the slow cases. They should

    76   // only be used when the fast cases failed. Use of these functions

    77   // without previous fast case check may cause fatal error.

    78   static void slow_enter(Handle obj, BasicLock* lock, TRAPS);

    79   static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);

    80 

    81   // Used only to handle jni locks or other unmatched monitor enter/exit

    82   // Internally they will use heavy weight monitor.

    83   static void jni_enter(Handle obj, TRAPS);

    84   static void jni_exit(oop obj, Thread* THREAD);

    85 

    86   // Handle all interpreter, compiler and jni cases

    87   static int  wait(Handle obj, jlong millis, TRAPS);

    88   static void notify(Handle obj, TRAPS);

    89   static void notifyall(Handle obj, TRAPS);

    90 

    91   static bool quick_notify(oopDesc* obj, Thread* Self, bool All);

    92   static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);

    93 

    94   // Special internal-use-only method for use by JVM infrastructure

    95   // that needs to wait() on a java-level object but that can't risk

    96   // throwing unexpected InterruptedExecutionExceptions.

    97   static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);

    98 

    99   // used by classloading to free classloader object lock,

   100   // wait on an internal lock, and reclaim original lock

   101   // with original recursion count

   102   static intptr_t complete_exit(Handle obj, TRAPS);

   103   static void reenter (Handle obj, intptr_t recursion, TRAPS);

   104 

   105   // thread-specific and global objectMonitor free list accessors

   106   static void verifyInUse(Thread * Self);

   107   static ObjectMonitor * omAlloc(Thread * Self);

   108   static void omRelease(Thread * Self, ObjectMonitor * m,

   109                         bool FromPerThreadAlloc);

   110   static void omFlush(Thread * Self);

   111 

   112   // Inflate light weight monitor to heavy weight monitor

   113   static ObjectMonitor* inflate(Thread * Self, oop obj, const InflateCause cause);

   114   // This version is only for internal use

   115   static ObjectMonitor* inflate_helper(oop obj);

   116   static const char* inflate_cause_name(const InflateCause cause);

   117 

   118   // Returns the identity hash value for an oop

   119   // NOTE: It may cause monitor inflation

   120   static intptr_t identity_hash_value_for(Handle obj);

   121   static intptr_t FastHashCode(Thread * Self, oop obj);

   122 

   123   // java.lang.Thread support

   124   static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);

   125   static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);

   126 

   127   static JavaThread* get_lock_owner(Handle h_obj, bool doLock);

   128 

   129   // JNI detach support

   130   static void release_monitors_owned_by_thread(TRAPS);

   131   static void monitors_iterate(MonitorClosure* m);

   132 

   133   // GC: we current use aggressive monitor deflation policy

   134   // Basically we deflate all monitors that are not busy.

   135   // An adaptive profile-based deflation policy could be used if needed

   136   static void deflate_idle_monitors(DeflateMonitorCounters* counters);

   137   static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);

   138   static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);

   139   static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);

   140 

   141   // For a given monitor list: global or per-thread, deflate idle monitors

   142   static int deflate_monitor_list(ObjectMonitor** listheadp,

   143                                   ObjectMonitor** freeHeadp,

   144                                   ObjectMonitor** freeTailp);

   145   static bool deflate_monitor(ObjectMonitor* mid, oop obj,

   146                               ObjectMonitor** freeHeadp,

   147                               ObjectMonitor** freeTailp);

   148   static bool is_cleanup_needed();

   149   static void oops_do(OopClosure* f);

   150   // Process oops in thread local used monitors

   151   static void thread_local_used_oops_do(Thread* thread, OopClosure* f);

   152 

   153   // debugging

   154   static void sanity_checks(const bool verbose,

   155                             const unsigned int cache_line_size,

   156                             int *error_cnt_ptr, int *warning_cnt_ptr);

   157   static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;

   158 

   159  private:

   160   enum { _BLOCKSIZE = 128 };

   161   // global list of blocks of monitors

   162   // gBlockList is really PaddedEnd<ObjectMonitor> *, but we don't

   163   // want to expose the PaddedEnd template more than necessary.

   164   static 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