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
 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 ObjectMonitorDeflationSafepointer;
 38 class ThreadsList;
 39 
 40 class MonitorList {
 41   friend class VMStructs;
 42 
 43 private:
 44   ObjectMonitor* volatile _head;
 45   volatile size_t _count;
 46   volatile size_t _max;
 47 
 48 public:
 49   void add(ObjectMonitor* monitor);
 50   size_t unlink_deflated(size_t deflated_count,
 51                          GrowableArray<ObjectMonitor*>* unlinked_list,
 52                          ObjectMonitorDeflationSafepointer* safepointer);
 53   size_t count() const;
 54   size_t max() const;
 55 
 56   class Iterator;
 57   Iterator iterator() const;
 58 };
 59 
 60 class MonitorList::Iterator {
 61   ObjectMonitor* _current;
 62 
 63 public:
 64   Iterator(ObjectMonitor* head) : _current(head) {}
 65   bool has_next() const { return _current != nullptr; }
 66   ObjectMonitor* next();
 67 };
 68 
 69 class ObjectSynchronizer : AllStatic {
 70   friend class VMStructs;
 71   friend class ObjectMonitorDeflationLogging;
 72 
 73  public:
 74   typedef enum {
 75     inflate_cause_vm_internal = 0,
 76     inflate_cause_monitor_enter = 1,
 77     inflate_cause_wait = 2,
 78     inflate_cause_notify = 3,
 79     inflate_cause_hash_code = 4,
 80     inflate_cause_jni_enter = 5,
 81     inflate_cause_jni_exit = 6,
 82     inflate_cause_nof = 7 // Number of causes

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