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   friend class WhiteBox;
 74 
 75  public:
 76   typedef enum {
 77     inflate_cause_vm_internal = 0,
 78     inflate_cause_monitor_enter = 1,
 79     inflate_cause_wait = 2,
 80     inflate_cause_notify = 3,
 81     inflate_cause_hash_code = 4,
 82     inflate_cause_jni_enter = 5,
 83     inflate_cause_jni_exit = 6,
 84     inflate_cause_nof = 7 // Number of causes
 85   } InflateCause;
 86 
 87   typedef enum {
 88     NOT_ENABLED    = 0,
 89     FATAL_EXIT     = 1,
 90     LOG_WARNING    = 2
 91   } SyncDiagnosticOption;
 92 
 93   // exit must be implemented non-blocking, since the compiler cannot easily handle
 94   // deoptimization at monitor exit. Hence, it does not take a Handle argument.
 95 
 96   // This is the "slow path" version of monitor enter and exit.
 97   static inline void enter(Handle obj, BasicLock* lock, JavaThread* current);
 98   static inline void exit(oop obj, BasicLock* lock, JavaThread* current);
 99 
100   // Used to enter a monitor for another thread. This requires that the
101   // locking_thread is suspended, and that entering on a potential
102   // inflated monitor may only contend with deflation. That is the obj being
103   // locked on is either already locked by the locking_thread or cannot
104   // escape the locking_thread.
105   static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
106 private:
107   // Shared implementation for enter and enter_for. Performs all but
108   // inflated monitor enter.
109   static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
110 
111   static bool quick_enter_legacy(oop obj, BasicLock* Lock, JavaThread* current);
112   static void enter_legacy(Handle obj, BasicLock* Lock, JavaThread* current);
113   static void exit_legacy(oop obj, BasicLock* lock, JavaThread* current);
114 public:
115   // Used only to handle jni locks or other unmatched monitor enter/exit
116   // Internally they will use heavy weight monitor.
117   static void jni_enter(Handle obj, JavaThread* current);
118   static void jni_exit(oop obj, TRAPS);
119 
120   // Handle all interpreter, compiler and jni cases
121   static int  wait(Handle obj, jlong millis, TRAPS);
122   static void notify(Handle obj, TRAPS);
123   static void notifyall(Handle obj, TRAPS);
124 
125   static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
126   static inline bool quick_enter(oop obj, BasicLock* Lock, JavaThread* current);
127 
128   // Special internal-use-only method for use by JVM infrastructure
129   // that needs to wait() on a java-level object but that can't risk
130   // throwing unexpected InterruptedExecutionExceptions.
131   static void waitUninterruptibly(Handle obj, jlong Millis, TRAPS);
132 
133   // Inflate light weight monitor to heavy weight monitor
134   static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
135   // Used to inflate a monitor as if it was done from the thread JavaThread.
136   static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
137 
138 private:
139   // Shared implementation between the different LockingMode.
140   static ObjectMonitor* inflate_impl(JavaThread* locking_thread, oop obj, const InflateCause cause);
141 
142 public:
143   // This version is only for internal use
144   static void inflate_helper(oop obj);
145   static const char* inflate_cause_name(const InflateCause cause);
146 
147   inline static ObjectMonitor* read_monitor(markWord mark);
148   inline static ObjectMonitor* read_monitor(Thread* current, oop obj, markWord mark);
149 
150   // Returns the identity hash value for an oop
151   // NOTE: It may cause monitor inflation
152   static intptr_t FastHashCode(Thread* current, oop obj);
153 
154   // java.lang.Thread support
155   static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
156 
157   static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
158 
159   // JNI detach support
160   static void release_monitors_owned_by_thread(JavaThread* current);
161 
162   // Iterate over all ObjectMonitors.
163   template <typename Function>
164   static void monitors_iterate(Function function);
165 
166   // Iterate ObjectMonitors owned by any thread and where the owner `filter`
167   // returns true.
168   template <typename OwnerFilter>
169   static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
170 
171   // Iterate ObjectMonitors where the owner is thread; this does NOT include
172   // ObjectMonitors where the owner is anonymous.
173   static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
174 
175   // Iterate ObjectMonitors where the owner is vthread.
176   static void owned_monitors_iterate(MonitorClosure* m, oop vthread);
177 
178   // Iterate ObjectMonitors owned by any thread.
179   static void owned_monitors_iterate(MonitorClosure* closure);
180 
181   // Initialize the gInflationLocks
182   static void initialize();
183 
184   // We currently use aggressive monitor deflation policy;
185   // basically we try to deflate all monitors that are not busy.
186   static size_t deflate_idle_monitors();
187 
188   // Deflate idle monitors:
189   static size_t deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer);
190   static size_t in_use_list_ceiling();
191   static void dec_in_use_list_ceiling();
192   static void inc_in_use_list_ceiling();
193   static void set_in_use_list_ceiling(size_t new_value);
194   static bool is_async_deflation_needed();
195   static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
196   static bool is_final_audit() { return _is_final_audit; }
197   static void set_is_final_audit() { _is_final_audit = true; }
198   static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
199   static void request_deflate_idle_monitors();
200   static bool request_deflate_idle_monitors_from_wb();  // for whitebox test support
201   static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
202   static jlong time_since_last_async_deflation_ms();
203 
204   // debugging
205   static void audit_and_print_stats(outputStream* out, bool on_exit);
206   static void chk_in_use_list(outputStream* out, int* error_cnt_p);
207   static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
208                                int* error_cnt_p);
209   static void do_final_audit_and_print_stats();
210   static void log_in_use_monitor_details(outputStream* out, bool log_all);
211 
212  private:
213   friend class SynchronizerTest;
214   friend class LightweightSynchronizer;
215 
216   static MonitorList _in_use_list;
217   static volatile bool _is_async_deflation_requested;
218   static volatile bool _is_final_audit;
219   static jlong         _last_async_deflation_time_ns;
220 
221   // Support for SynchronizerTest access to GVars fields:
222   static u_char* get_gvars_addr();
223   static u_char* get_gvars_hc_sequence_addr();
224   static size_t get_gvars_size();
225   static u_char* get_gvars_stw_random_addr();
226 
227   static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
228 };
229 
230 // ObjectLocker enforces balanced locking and can never throw an
231 // IllegalMonitorStateException. However, a pending exception may
232 // have to pass through, and we must also be able to deal with
233 // asynchronous exceptions. The caller is responsible for checking
234 // the thread's pending exception if needed.
235 // When using ObjectLocker the top native frames in the stack will
236 // not be seen in case we attempt preemption, since we start walking
237 // from the last Java anchor, so we disable it with NoPreemptMark.
238 class ObjectLocker : public StackObj {
239  private:
240   JavaThread* _thread;
241   Handle      _obj;
242   BasicLock   _lock;
243   NoPreemptMark _npm;
244  public:
245   ObjectLocker(Handle obj, JavaThread* current);
246   ~ObjectLocker();
247 
248   // Monitor behavior
249   void wait(TRAPS)  { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
250   void wait_uninterruptibly(TRAPS)  { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); } // wait forever
251   void notify_all(TRAPS)  { ObjectSynchronizer::notifyall(_obj, CHECK); }
252 };
253 
254 // Interface to visit monitors
255 class ObjectMonitorsView {
256 public:
257   // Visit monitors that belong to the given thread
258   virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
259 };
260 
261 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP
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