1 /*
  2  * Copyright (c) 1998, 2024, 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
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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/markWord.hpp"
 30 #include "runtime/basicLock.hpp"
 31 #include "runtime/handles.hpp"
 32 #include "runtime/javaThread.hpp"
 33 #include "utilities/resourceHash.hpp"
 34 
 35 template <typename T> class GrowableArray;
 36 class LogStream;
 37 class ObjectMonitor;
 38 class ObjectMonitorDeflationSafepointer;
 39 class ThreadsList;
 40 
 41 class MonitorList {
 42   friend class VMStructs;
 43 
 44 private:
 45   ObjectMonitor* volatile _head;
 46   volatile size_t _count;
 47   volatile size_t _max;
 48 
 49 public:
 50   void add(ObjectMonitor* monitor);
 51   size_t unlink_deflated(size_t deflated_count,
 52                          GrowableArray<ObjectMonitor*>* unlinked_list,
 53                          ObjectMonitorDeflationSafepointer* safepointer);
 54   size_t count() const;
 55   size_t max() const;
 56 
 57   class Iterator;
 58   Iterator iterator() const;
 59 };
 60 
 61 class MonitorList::Iterator {
 62   ObjectMonitor* _current;
 63 
 64 public:
 65   Iterator(ObjectMonitor* head) : _current(head) {}
 66   bool has_next() const { return _current != nullptr; }
 67   ObjectMonitor* next();
 68 };
 69 
 70 class ObjectSynchronizer : AllStatic {
 71   friend class VMStructs;
 72   friend class ObjectMonitorDeflationLogging;
 73 
 74  public:
 75   typedef enum {
 76     inflate_cause_vm_internal = 0,
 77     inflate_cause_monitor_enter = 1,
 78     inflate_cause_wait = 2,
 79     inflate_cause_notify = 3,
 80     inflate_cause_hash_code = 4,
 81     inflate_cause_jni_enter = 5,
 82     inflate_cause_jni_exit = 6,
 83     inflate_cause_nof = 7 // Number of causes
 84   } InflateCause;
 85 
 86   typedef enum {
 87     NOT_ENABLED    = 0,
 88     FATAL_EXIT     = 1,
 89     LOG_WARNING    = 2
 90   } SyncDiagnosticOption;
 91 
 92   // exit must be implemented non-blocking, since the compiler cannot easily handle
 93   // deoptimization at monitor exit. Hence, it does not take a Handle argument.
 94 
 95   // This is the "slow path" version of monitor enter and exit.
 96   static inline void enter(Handle obj, BasicLock* lock, JavaThread* current);
 97   static inline void exit(oop obj, BasicLock* lock, JavaThread* current);
 98 
 99   // Used to enter a monitor for another thread. This requires that the
100   // locking_thread is suspended, and that entering on a potential
101   // inflated monitor may only contend with deflation. That is the obj being
102   // locked on is either already locked by the locking_thread or cannot
103   // escape the locking_thread.
104   static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
105 private:
106   // Shared implementation for enter and enter_for. Performs all but
107   // inflated monitor enter.
108   static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
109 
110   static bool quick_enter_legacy(oop obj, JavaThread* current, BasicLock* Lock);
111   static void enter_legacy(Handle obj, BasicLock* Lock, JavaThread* current);
112   static void exit_legacy(oop obj, BasicLock* lock, JavaThread* current);
113 public:
114   // Used only to handle jni locks or other unmatched monitor enter/exit
115   // Internally they will use heavy weight monitor.
116   static void jni_enter(Handle obj, JavaThread* current);
117   static void jni_exit(oop obj, TRAPS);
118 
119   // Handle all interpreter, compiler and jni cases
120   static int  wait(Handle obj, jlong millis, TRAPS);
121   static void notify(Handle obj, TRAPS);
122   static void notifyall(Handle obj, TRAPS);
123 
124   static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
125   static inline bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
126 
127   // Inflate light weight monitor to heavy weight monitor
128   static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
129   // Used to inflate a monitor as if it was done from the thread JavaThread.
130   static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
131 
132 private:
133   // Shared implementation between the different LockingMode.
134   static ObjectMonitor* inflate_impl(oop obj, const InflateCause cause);
135 
136 public:
137   // This version is only for internal use
138   static void inflate_helper(oop obj);
139   static const char* inflate_cause_name(const InflateCause cause);
140 
141   inline static ObjectMonitor* read_monitor(markWord mark);
142   inline static ObjectMonitor* read_monitor(Thread* current, oop obj, markWord mark);
143 
144   // Returns the identity hash value for an oop
145   // NOTE: It may cause monitor inflation
146   static intptr_t FastHashCode(Thread* current, oop obj);
147 
148   // java.lang.Thread support
149   static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
150 
151   static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
152 
153   // JNI detach support
154   static void release_monitors_owned_by_thread(JavaThread* current);
155 
156   // Iterate over all ObjectMonitors.
157   template <typename Function>
158   static void monitors_iterate(Function function);
159 
160   // Iterate ObjectMonitors owned by any thread and where the owner `filter`
161   // returns true.
162   template <typename OwnerFilter>
163   static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
164 
165   // Iterate ObjectMonitors where the owner == thread; this does NOT include
166   // ObjectMonitors where owner is set to a stack lock address in thread.
167   static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
168 
169   // Iterate ObjectMonitors owned by any thread.
170   static void owned_monitors_iterate(MonitorClosure* closure);
171 
172   // Initialize the gInflationLocks
173   static void initialize();
174 
175   // We currently use aggressive monitor deflation policy;
176   // basically we try to deflate all monitors that are not busy.
177   static size_t deflate_idle_monitors();
178 
179   // Deflate idle monitors:
180   static size_t deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer);
181   static size_t in_use_list_ceiling();
182   static void dec_in_use_list_ceiling();
183   static void inc_in_use_list_ceiling();
184   static void set_in_use_list_ceiling(size_t new_value);
185   static bool is_async_deflation_needed();
186   static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
187   static bool is_final_audit() { return _is_final_audit; }
188   static void set_is_final_audit() { _is_final_audit = true; }
189   static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
190   static void request_deflate_idle_monitors();
191   static bool request_deflate_idle_monitors_from_wb();  // for whitebox test support
192   static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
193   static jlong time_since_last_async_deflation_ms();
194 
195   // debugging
196   static void audit_and_print_stats(outputStream* out, bool on_exit);
197   static void chk_in_use_list(outputStream* out, int* error_cnt_p);
198   static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
199                                int* error_cnt_p);
200   static void do_final_audit_and_print_stats();
201   static void log_in_use_monitor_details(outputStream* out, bool log_all);
202 
203  private:
204   friend class SynchronizerTest;
205   friend class LightweightSynchronizer;
206 
207   static MonitorList _in_use_list;
208   static volatile bool _is_async_deflation_requested;
209   static volatile bool _is_final_audit;
210   static jlong         _last_async_deflation_time_ns;
211 
212   // Support for SynchronizerTest access to GVars fields:
213   static u_char* get_gvars_addr();
214   static u_char* get_gvars_hc_sequence_addr();
215   static size_t get_gvars_size();
216   static u_char* get_gvars_stw_random_addr();
217 
218   static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
219 };
220 
221 // ObjectLocker enforces balanced locking and can never throw an
222 // IllegalMonitorStateException. However, a pending exception may
223 // have to pass through, and we must also be able to deal with
224 // asynchronous exceptions. The caller is responsible for checking
225 // the thread's pending exception if needed.
226 class ObjectLocker : public StackObj {
227  private:
228   JavaThread* _thread;
229   Handle      _obj;
230   BasicLock   _lock;
231  public:
232   ObjectLocker(Handle obj, JavaThread* current);
233   ~ObjectLocker();
234 
235   // Monitor behavior
236   void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
237   void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
238 };
239 
240 // Interface to visit monitors
241 class ObjectMonitorsView {
242 public:
243   // Visit monitors that belong to the given thread
244   virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
245 };
246 
247 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP
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