1 /*
2 * Copyright (c) 1998, 2019, 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.
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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 "runtime/perfData.hpp"
33
34 class ObjectMonitor;
35 class ObjectMonitorHandle;
36 class ThreadsList;
37
38 #ifndef OM_CACHE_LINE_SIZE
39 // Use DEFAULT_CACHE_LINE_SIZE if not already specified for
40 // the current build platform.
41 #define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
42 #endif
43
44 typedef PaddedEnd<ObjectMonitor, OM_CACHE_LINE_SIZE> PaddedObjectMonitor;
45
46 struct DeflateMonitorCounters {
47 volatile int n_in_use; // currently associated with objects
48 volatile int n_in_circulation; // extant
49 volatile int n_scavenged; // reclaimed (global and per-thread)
50 volatile int per_thread_scavenged; // per-thread scavenge total
51 double per_thread_times; // per-thread scavenge times
52 };
53
54 class ObjectSynchronizer : AllStatic {
55 friend class VMStructs;
56 public:
57 typedef enum {
58 owner_self,
59 owner_none,
60 owner_other
61 } LockOwnership;
62
63 typedef enum {
64 inflate_cause_vm_internal = 0,
65 inflate_cause_monitor_enter = 1,
66 inflate_cause_wait = 2,
67 inflate_cause_notify = 3,
68 inflate_cause_hash_code = 4,
69 inflate_cause_jni_enter = 5,
70 inflate_cause_jni_exit = 6,
71 inflate_cause_nof = 7 // Number of causes
72 } InflateCause;
73
74 // exit must be implemented non-blocking, since the compiler cannot easily handle
75 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
76
77 // This is full version of monitor enter and exit. I choose not
78 // to use enter() and exit() in order to make sure user be ware
79 // of the performance and semantics difference. They are normally
80 // used by ObjectLocker etc. The interpreter and compiler use
81 // assembly copies of these routines. Please keep them synchronized.
82 //
83 // attempt_rebias flag is used by UseBiasedLocking implementation
84 static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
85 TRAPS);
86 static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);
87
88 // WARNING: They are ONLY used to handle the slow cases. They should
89 // only be used when the fast cases failed. Use of these functions
90 // without previous fast case check may cause fatal error.
91 static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
92 static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);
93
94 // Used only to handle jni locks or other unmatched monitor enter/exit
95 // Internally they will use heavy weight monitor.
96 static void jni_enter(Handle obj, TRAPS);
97 static void jni_exit(oop obj, Thread* THREAD);
98
99 // Handle all interpreter, compiler and jni cases
100 static int wait(Handle obj, jlong millis, TRAPS);
101 static void notify(Handle obj, TRAPS);
102 static void notifyall(Handle obj, TRAPS);
103
104 static bool quick_notify(oopDesc* obj, Thread* self, bool All);
105 static bool quick_enter(oop obj, Thread* self, BasicLock* Lock);
106
107 // Special internal-use-only method for use by JVM infrastructure
108 // that needs to wait() on a java-level object but that can't risk
109 // throwing unexpected InterruptedExecutionExceptions.
110 static void wait_uninterruptibly(Handle obj, jlong Millis, Thread* THREAD);
111
112 // used by classloading to free classloader object lock,
113 // wait on an internal lock, and reclaim original lock
114 // with original recursion count
115 static intptr_t complete_exit(Handle obj, TRAPS);
116 static void reenter (Handle obj, intptr_t recursion, TRAPS);
117
118 // thread-specific and global ObjectMonitor free list accessors
119 static ObjectMonitor* om_alloc(Thread* self, const InflateCause cause);
120 static void om_release(Thread* self, ObjectMonitor* m,
121 bool FromPerThreadAlloc);
122 static void om_flush(Thread* self);
123
124 // Inflate light weight monitor to heavy weight monitor
125 static void inflate(ObjectMonitorHandle* omh_p, Thread* self, oop obj,
126 const InflateCause cause);
127 // This version is only for internal use
128 static void inflate_helper(ObjectMonitorHandle* omh_p, oop obj);
129 static const char* inflate_cause_name(const InflateCause cause);
130
131 // Returns the identity hash value for an oop
132 // NOTE: It may cause monitor inflation
133 static intptr_t identity_hash_value_for(Handle obj);
134 static intptr_t FastHashCode(Thread* self, oop obj);
135
136 // java.lang.Thread support
137 static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
138 static LockOwnership query_lock_ownership(JavaThread* self, Handle h_obj);
139
140 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
141
142 // JNI detach support
143 static void release_monitors_owned_by_thread(TRAPS);
144 static void monitors_iterate(MonitorClosure* m);
145
146 // GC: we current use aggressive monitor deflation policy
147 // Basically we deflate all monitors that are not busy.
148 // An adaptive profile-based deflation policy could be used if needed
149 static void deflate_idle_monitors(DeflateMonitorCounters* counters);
150 static void deflate_global_idle_monitors_using_JT();
151 static void deflate_per_thread_idle_monitors_using_JT(JavaThread* target);
152 static void deflate_common_idle_monitors_using_JT(bool is_global, JavaThread* target);
153 static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
154 static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
155 static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
156
157 // For a given monitor list: global or per-thread, deflate idle monitors
158 static int deflate_monitor_list(ObjectMonitor* volatile * list_p,
159 int volatile * count_p,
160 ObjectMonitor** free_head_p,
161 ObjectMonitor** free_tail_p);
162 // For a given in-use monitor list: global or per-thread, deflate idle
163 // monitors using a JavaThread.
164 static int deflate_monitor_list_using_JT(ObjectMonitor* volatile * list_p,
165 int volatile * count_p,
166 ObjectMonitor** free_head_p,
167 ObjectMonitor** free_tail_p,
168 ObjectMonitor** saved_mid_in_use_p);
169 static bool deflate_monitor(ObjectMonitor* mid, oop obj,
170 ObjectMonitor** free_head_p,
171 ObjectMonitor** free_tail_p);
172 static bool deflate_monitor_using_JT(ObjectMonitor* mid,
173 ObjectMonitor** free_head_p,
174 ObjectMonitor** free_tail_p);
175 static bool is_async_deflation_needed();
176 static bool is_safepoint_deflation_needed();
177 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
178 static bool is_special_deflation_requested() { return _is_special_deflation_requested; }
179 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
180 static void set_is_special_deflation_requested(bool new_value) { _is_special_deflation_requested = new_value; }
181 static jlong time_since_last_async_deflation_ms();
182 static void oops_do(OopClosure* f);
183 // Process oops in thread local used monitors
184 static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
185
186 // debugging
187 static void audit_and_print_stats(bool on_exit);
188 static void chk_free_entry(JavaThread* jt, ObjectMonitor* n,
189 outputStream * out, int *error_cnt_p);
190 static void chk_global_free_list_and_count(outputStream * out,
191 int *error_cnt_p);
192 static void chk_global_in_use_list_and_count(outputStream * out,
193 int *error_cnt_p);
194 static void chk_in_use_entry(JavaThread* jt, ObjectMonitor* n,
195 outputStream * out, int *error_cnt_p);
196 static void chk_per_thread_in_use_list_and_count(JavaThread *jt,
197 outputStream * out,
198 int *error_cnt_p);
199 static void chk_per_thread_free_list_and_count(JavaThread *jt,
200 outputStream * out,
201 int *error_cnt_p);
202 static void log_in_use_monitor_details(outputStream * out);
203 static int log_monitor_list_counts(outputStream * out);
204 static int verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
205
206 static void do_safepoint_work(DeflateMonitorCounters* counters);
207
208 private:
209 friend class SynchronizerTest;
210
211 enum { _BLOCKSIZE = 128 };
212 // global list of blocks of monitors
213 static PaddedObjectMonitor* volatile g_block_list;
214 static volatile bool _is_async_deflation_requested;
215 static volatile bool _is_special_deflation_requested;
216 static jlong _last_async_deflation_time_ns;
217
218 // Function to prepend new blocks to the appropriate lists:
219 static void prepend_block_to_lists(PaddedObjectMonitor* new_blk);
220
221 // Process oops in all global used monitors (i.e. moribund thread's monitors)
222 static void global_used_oops_do(OopClosure* f);
223 // Process oops in monitors on the given list
224 static void list_oops_do(ObjectMonitor* list, int count, OopClosure* f);
225
226 // Support for SynchronizerTest access to GVars fields:
227 static u_char* get_gvars_addr();
228 static u_char* get_gvars_hc_sequence_addr();
229 static size_t get_gvars_size();
230 static u_char* get_gvars_stw_random_addr();
231 };
232
233 // ObjectLocker enforces balanced locking and can never throw an
234 // IllegalMonitorStateException. However, a pending exception may
235 // have to pass through, and we must also be able to deal with
236 // asynchronous exceptions. The caller is responsible for checking
237 // the thread's pending exception if needed.
238 class ObjectLocker : public StackObj {
239 private:
240 Thread* _thread;
241 Handle _obj;
242 BasicLock _lock;
243 bool _dolock; // default true
244 public:
245 ObjectLocker(Handle obj, Thread* thread, bool do_lock = true);
246 ~ObjectLocker();
247
248 // Monitor behavior
249 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
250 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
251 void wait_uninterruptibly(TRAPS) { ObjectSynchronizer::wait_uninterruptibly(_obj, 0, CHECK); }
252 // complete_exit gives up lock completely, returning recursion count
253 // reenter reclaims lock with original recursion count
254 intptr_t complete_exit(TRAPS) { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
255 void reenter(intptr_t recursion, TRAPS) { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
256 };
257
258 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP