1 /*
  2  * Copyright (c) 1998, 2023, 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.
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 23  */
 24 
 25 #ifndef SHARE_RUNTIME_SYNCHRONIZER_HPP
 26 #define SHARE_RUNTIME_SYNCHRONIZER_HPP
 27 
 28 #include "memory/padded.hpp"
 29 #include "oops/markWord.hpp"
 30 #include "runtime/basicLock.hpp"
 31 #include "runtime/handles.hpp"
 32 #include "utilities/resourceHash.hpp"
 33 
 34 template <typename T> class GrowableArray;
 35 class LogStream;
 36 class ObjectMonitor;
 37 class ThreadsList;
 38 
 39 class MonitorList {
 40   friend class VMStructs;
 41 
 42 private:
 43   ObjectMonitor* volatile _head;
 44   volatile size_t _count;
 45   volatile size_t _max;
 46 
 47 public:
 48   void add(ObjectMonitor* monitor);
 49   size_t unlink_deflated(Thread* current, LogStream* ls, elapsedTimer* timer_p,
 50                          size_t deflated_count,
 51                          GrowableArray<ObjectMonitor*>* unlinked_list);
 52   size_t count() const;
 53   size_t max() const;
 54 
 55   class Iterator;
 56   Iterator iterator() const;
 57 };
 58 
 59 class MonitorList::Iterator {
 60   ObjectMonitor* _current;
 61 
 62 public:
 63   Iterator(ObjectMonitor* head) : _current(head) {}
 64   bool has_next() const { return _current != nullptr; }
 65   ObjectMonitor* next();
 66 };
 67 
 68 class ObjectSynchronizer : AllStatic {
 69   friend class VMStructs;
 70 
 71  public:
 72   typedef enum {
 73     inflate_cause_vm_internal = 0,
 74     inflate_cause_monitor_enter = 1,
 75     inflate_cause_wait = 2,
 76     inflate_cause_notify = 3,
 77     inflate_cause_hash_code = 4,
 78     inflate_cause_jni_enter = 5,
 79     inflate_cause_jni_exit = 6,
 80     inflate_cause_nof = 7 // Number of causes
 81   } InflateCause;
 82 
 83   typedef enum {
 84     NOT_ENABLED    = 0,
 85     FATAL_EXIT     = 1,
 86     LOG_WARNING    = 2
 87   } SyncDiagnosticOption;
 88 
 89   // exit must be implemented non-blocking, since the compiler cannot easily handle
 90   // deoptimization at monitor exit. Hence, it does not take a Handle argument.
 91 
 92   // This is the "slow path" version of monitor enter and exit.
 93   static void enter(Handle obj, BasicLock* lock, JavaThread* current);
 94   static void exit(oop obj, BasicLock* lock, JavaThread* current);
 95 
 96   // Used only to handle jni locks or other unmatched monitor enter/exit
 97   // Internally they will use heavy weight monitor.
 98   static void jni_enter(Handle obj, JavaThread* current);
 99   static void jni_exit(oop obj, TRAPS);
100 
101   // Handle all interpreter, compiler and jni cases
102   static int  wait(Handle obj, jlong millis, TRAPS);
103   static void notify(Handle obj, TRAPS);
104   static void notifyall(Handle obj, TRAPS);
105 
106   static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
107   static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
108 
109   // Inflate light weight monitor to heavy weight monitor
110   static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
111   // This version is only for internal use
112   static void inflate_helper(oop obj);
113   static const char* inflate_cause_name(const InflateCause cause);
114 
115   // Returns the identity hash value for an oop
116   // NOTE: It may cause monitor inflation
117   static intptr_t FastHashCode(Thread* current, oop obj);
118 
119   // java.lang.Thread support
120   static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
121 
122   static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
123 
124   // JNI detach support
125   static void release_monitors_owned_by_thread(JavaThread* current);
126 
127   // Iterate over all ObjectMonitors.
128   template <typename Function>
129   static void monitors_iterate(Function function);
130 
131   // Iterate ObjectMonitors owned by any thread and where the owner `filter`
132   // returns true.
133   template <typename OwnerFilter>
134   static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
135 
136   // Iterate ObjectMonitors where the owner == thread; this does NOT include
137   // ObjectMonitors where owner is set to a stack lock address in thread.
138   static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
139 
140   // Iterate ObjectMonitors owned by any thread.
141   static void owned_monitors_iterate(MonitorClosure* closure);
142 
143   // Initialize the gInflationLocks
144   static void initialize();
145 
146   // We currently use aggressive monitor deflation policy;
147   // basically we try to deflate all monitors that are not busy.
148   static size_t deflate_idle_monitors();
149 
150   // Deflate idle monitors:
151   static void chk_for_block_req(JavaThread* current, const char* op_name,
152                                 const char* cnt_name, size_t cnt, LogStream* ls,
153                                 elapsedTimer* timer_p);
154   static size_t deflate_monitor_list(Thread* current, LogStream* ls, elapsedTimer* timer_p);
155   static size_t in_use_list_ceiling();
156   static void dec_in_use_list_ceiling();
157   static void inc_in_use_list_ceiling();
158   static void set_in_use_list_ceiling(size_t new_value);
159   static bool is_async_deflation_needed();
160   static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
161   static bool is_final_audit() { return _is_final_audit; }
162   static void set_is_final_audit() { _is_final_audit = true; }
163   static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
164   static void request_deflate_idle_monitors();
165   static bool request_deflate_idle_monitors_from_wb();  // for whitebox test support
166   static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
167   static jlong time_since_last_async_deflation_ms();
168 
169   // debugging
170   static void audit_and_print_stats(bool on_exit);
171   static void chk_in_use_list(outputStream* out, int* error_cnt_p);
172   static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
173                                int* error_cnt_p);
174   static void do_final_audit_and_print_stats();
175   static void log_in_use_monitor_details(outputStream* out, bool log_all);
176 
177  private:
178   friend class SynchronizerTest;
179 
180   static MonitorList _in_use_list;
181   static volatile bool _is_async_deflation_requested;
182   static volatile bool _is_final_audit;
183   static jlong         _last_async_deflation_time_ns;
184 
185   // Support for SynchronizerTest access to GVars fields:
186   static u_char* get_gvars_addr();
187   static u_char* get_gvars_hc_sequence_addr();
188   static size_t get_gvars_size();
189   static u_char* get_gvars_stw_random_addr();
190 
191   static void handle_sync_on_value_based_class(Handle obj, JavaThread* current);
192 };
193 
194 // ObjectLocker enforces balanced locking and can never throw an
195 // IllegalMonitorStateException. However, a pending exception may
196 // have to pass through, and we must also be able to deal with
197 // asynchronous exceptions. The caller is responsible for checking
198 // the thread's pending exception if needed.
199 class ObjectLocker : public StackObj {
200  private:
201   JavaThread* _thread;
202   Handle      _obj;
203   BasicLock   _lock;
204  public:
205   ObjectLocker(Handle obj, JavaThread* current);
206   ~ObjectLocker();
207 
208   // Monitor behavior
209   void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
210   void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
211 };
212 
213 // Interface to visit monitors
214 class ObjectMonitorsView {
215 public:
216   // Visit monitors that belong to the given thread
217   virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
218 };
219 
220 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP