Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp @ 6615:09aad8452938
7190310: Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops
Summary: In C2 add software membar after load from Reference.referent field to prevent commoning of loads across safepoint since GC can change its value. In C1 always generate Reference.get() intrinsic.
Reviewed-by: roland, twisti, dholmes, johnc
author | kvn |
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date | Mon, 20 Aug 2012 09:58:58 -0700 |
parents | f08d439fab8c |
children | f34d701e952e |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP |
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP | |
27 | |
28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp" | |
29 #include "gc_implementation/shared/concurrentGCThread.hpp" | |
30 #ifdef TARGET_OS_FAMILY_linux | |
31 # include "thread_linux.inline.hpp" | |
32 #endif | |
33 #ifdef TARGET_OS_FAMILY_solaris | |
34 # include "thread_solaris.inline.hpp" | |
35 #endif | |
36 #ifdef TARGET_OS_FAMILY_windows | |
37 # include "thread_windows.inline.hpp" | |
38 #endif | |
3960 | 39 #ifdef TARGET_OS_FAMILY_bsd |
40 # include "thread_bsd.inline.hpp" | |
41 #endif | |
1972 | 42 |
0 | 43 class ConcurrentMarkSweepGeneration; |
44 class CMSCollector; | |
45 | |
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46 // The Concurrent Mark Sweep GC Thread |
0 | 47 class ConcurrentMarkSweepThread: public ConcurrentGCThread { |
48 friend class VMStructs; | |
49 friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship | |
50 friend class CMSCollector; | |
51 public: | |
52 virtual void run(); | |
53 | |
54 private: | |
55 static ConcurrentMarkSweepThread* _cmst; | |
56 static CMSCollector* _collector; | |
57 static SurrogateLockerThread* _slt; | |
58 static SurrogateLockerThread::SLT_msg_type _sltBuffer; | |
59 static Monitor* _sltMonitor; | |
60 | |
61 static bool _should_terminate; | |
62 | |
63 enum CMS_flag_type { | |
64 CMS_nil = NoBits, | |
65 CMS_cms_wants_token = nth_bit(0), | |
66 CMS_cms_has_token = nth_bit(1), | |
67 CMS_vm_wants_token = nth_bit(2), | |
68 CMS_vm_has_token = nth_bit(3) | |
69 }; | |
70 | |
71 static int _CMS_flag; | |
72 | |
73 static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; } | |
74 static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; } | |
75 static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; } | |
76 void sleepBeforeNextCycle(); | |
77 | |
78 // CMS thread should yield for a young gen collection, direct allocation, | |
79 // and iCMS activity. | |
80 static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing | |
81 static volatile jint _pending_yields; | |
82 static volatile jint _pending_decrements; // decrements to _pending_yields | |
83 static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing | |
84 | |
85 // Tracing messages, enabled by CMSTraceThreadState. | |
86 static inline void trace_state(const char* desc); | |
87 | |
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88 static volatile int _icms_disabled; // a counter to track #iCMS disable & enable |
0 | 89 static volatile bool _should_run; // iCMS may run |
90 static volatile bool _should_stop; // iCMS should stop | |
91 | |
92 // debugging | |
93 void verify_ok_to_terminate() const PRODUCT_RETURN; | |
94 | |
95 public: | |
96 // Constructor | |
97 ConcurrentMarkSweepThread(CMSCollector* collector); | |
98 | |
99 static void makeSurrogateLockerThread(TRAPS); | |
100 static SurrogateLockerThread* slt() { return _slt; } | |
101 | |
102 // Tester | |
103 bool is_ConcurrentGC_thread() const { return true; } | |
104 | |
105 static void threads_do(ThreadClosure* tc); | |
106 | |
107 // Printing | |
108 void print_on(outputStream* st) const; | |
109 void print() const { print_on(tty); } | |
110 static void print_all_on(outputStream* st); | |
111 static void print_all() { print_all_on(tty); } | |
112 | |
113 // Returns the CMS Thread | |
114 static ConcurrentMarkSweepThread* cmst() { return _cmst; } | |
115 static CMSCollector* collector() { return _collector; } | |
116 | |
117 // Create and start the CMS Thread, or stop it on shutdown | |
118 static ConcurrentMarkSweepThread* start(CMSCollector* collector); | |
119 static void stop(); | |
120 static bool should_terminate() { return _should_terminate; } | |
121 | |
122 // Synchronization using CMS token | |
123 static void synchronize(bool is_cms_thread); | |
124 static void desynchronize(bool is_cms_thread); | |
125 static bool vm_thread_has_cms_token() { | |
126 return CMS_flag_is_set(CMS_vm_has_token); | |
127 } | |
128 static bool cms_thread_has_cms_token() { | |
129 return CMS_flag_is_set(CMS_cms_has_token); | |
130 } | |
131 static bool vm_thread_wants_cms_token() { | |
132 return CMS_flag_is_set(CMS_vm_wants_token); | |
133 } | |
134 static bool cms_thread_wants_cms_token() { | |
135 return CMS_flag_is_set(CMS_cms_wants_token); | |
136 } | |
137 | |
138 // Wait on CMS lock until the next synchronous GC | |
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139 // or given timeout, whichever is earlier. A timeout value |
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140 // of 0 indicates that there is no upper bound on the wait time. |
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141 // A concurrent full gc request terminates the wait. |
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142 void wait_on_cms_lock(long t_millis); |
0 | 143 |
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144 // The CMS thread will yield during the work portion of its cycle |
0 | 145 // only when requested to. Both synchronous and asychronous requests |
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146 // are provided: |
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147 // (1) A synchronous request is used for young gen collections and |
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148 // for direct allocations. The requesting thread increments |
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149 // _pending_yields at the beginning of an operation, and decrements |
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150 // _pending_yields when that operation is completed. |
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151 // In turn, the CMS thread yields when _pending_yields is positive, |
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152 // and continues to yield until the value reverts to 0. |
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153 // (2) An asynchronous request, on the other hand, is used by iCMS |
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154 // for the stop_icms() operation. A single yield satisfies all of |
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155 // the outstanding asynch yield requests, of which there may |
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156 // occasionally be several in close succession. To accomplish |
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157 // this, an asynch-requesting thread atomically increments both |
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158 // _pending_yields and _pending_decrements. An asynchr requesting |
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159 // thread does not wait and "acknowledge" completion of an operation |
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160 // and deregister the request, like the synchronous version described |
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161 // above does. In turn, after yielding, the CMS thread decrements both |
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162 // _pending_yields and _pending_decrements by the value seen in |
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163 // _pending_decrements before the decrement. |
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164 // NOTE: The above scheme is isomorphic to having two request counters, |
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165 // one for async requests and one for sync requests, and for the CMS thread |
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166 // to check the sum of the two counters to decide whether it should yield |
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167 // and to clear only the async counter when it yields. However, it turns out |
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168 // to be more efficient for CMS code to just check a single counter |
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169 // _pending_yields that holds the sum (of both sync and async requests), and |
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170 // a second counter _pending_decrements that only holds the async requests, |
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171 // for greater efficiency, since in a typical CMS run, there are many more |
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172 // pontential (i.e. static) yield points than there are actual |
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173 // (i.e. dynamic) yields because of requests, which are few and far between. |
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174 // |
0 | 175 // Note that, while "_pending_yields >= _pending_decrements" is an invariant, |
176 // we cannot easily test that invariant, since the counters are manipulated via | |
177 // atomic instructions without explicit locking and we cannot read | |
178 // the two counters atomically together: one suggestion is to | |
179 // use (for example) 16-bit counters so as to be able to read the | |
180 // two counters atomically even on 32-bit platforms. Notice that | |
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181 // the second assert in acknowledge_yield_request() below does indeed |
0 | 182 // check a form of the above invariant, albeit indirectly. |
183 | |
184 static void increment_pending_yields() { | |
185 Atomic::inc(&_pending_yields); | |
186 assert(_pending_yields >= 0, "can't be negative"); | |
187 } | |
188 static void decrement_pending_yields() { | |
189 Atomic::dec(&_pending_yields); | |
190 assert(_pending_yields >= 0, "can't be negative"); | |
191 } | |
192 static void asynchronous_yield_request() { | |
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193 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
0 | 194 increment_pending_yields(); |
195 Atomic::inc(&_pending_decrements); | |
196 assert(_pending_decrements >= 0, "can't be negative"); | |
197 } | |
198 static void acknowledge_yield_request() { | |
199 jint decrement = _pending_decrements; | |
200 if (decrement > 0) { | |
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201 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
0 | 202 // Order important to preserve: _pending_yields >= _pending_decrements |
203 Atomic::add(-decrement, &_pending_decrements); | |
204 Atomic::add(-decrement, &_pending_yields); | |
205 assert(_pending_decrements >= 0, "can't be negative"); | |
206 assert(_pending_yields >= 0, "can't be negative"); | |
207 } | |
208 } | |
209 static bool should_yield() { return _pending_yields > 0; } | |
210 | |
211 // CMS incremental mode. | |
212 static void start_icms(); // notify thread to start a quantum of work | |
213 static void stop_icms(); // request thread to stop working | |
214 void icms_wait(); // if asked to stop, wait until notified to start | |
215 | |
216 // Incremental mode is enabled globally by the flag CMSIncrementalMode. It | |
217 // must also be enabled/disabled dynamically to allow foreground collections. | |
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218 #define ICMS_ENABLING_ASSERT \ |
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219 assert((CMSIncrementalMode && _icms_disabled >= 0) || \ |
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220 (!CMSIncrementalMode && _icms_disabled <= 0), "Error") |
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221 |
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222 static inline void enable_icms() { |
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223 ICMS_ENABLING_ASSERT; |
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224 Atomic::dec(&_icms_disabled); |
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225 } |
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226 static inline void disable_icms() { |
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227 ICMS_ENABLING_ASSERT; |
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228 Atomic::inc(&_icms_disabled); |
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229 } |
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230 static inline bool icms_is_disabled() { |
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231 ICMS_ENABLING_ASSERT; |
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232 return _icms_disabled > 0; |
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233 } |
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234 static inline bool icms_is_enabled() { |
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235 return !icms_is_disabled(); |
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236 } |
0 | 237 }; |
238 | |
239 inline void ConcurrentMarkSweepThread::trace_state(const char* desc) { | |
240 if (CMSTraceThreadState) { | |
241 char buf[128]; | |
242 TimeStamp& ts = gclog_or_tty->time_stamp(); | |
243 if (!ts.is_updated()) { | |
244 ts.update(); | |
245 } | |
246 jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ", | |
247 ts.seconds(), desc); | |
248 buf[sizeof(buf) - 1] = '\0'; | |
249 gclog_or_tty->print(buf); | |
250 } | |
251 } | |
252 | |
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253 // For scoped increment/decrement of (synchronous) yield requests |
0 | 254 class CMSSynchronousYieldRequest: public StackObj { |
255 public: | |
256 CMSSynchronousYieldRequest() { | |
257 ConcurrentMarkSweepThread::increment_pending_yields(); | |
258 } | |
259 ~CMSSynchronousYieldRequest() { | |
260 ConcurrentMarkSweepThread::decrement_pending_yields(); | |
261 } | |
262 }; | |
263 | |
264 // Used to emit a warning in case of unexpectedly excessive | |
265 // looping (in "apparently endless loops") in CMS code. | |
266 class CMSLoopCountWarn: public StackObj { | |
267 private: | |
268 const char* _src; | |
269 const char* _msg; | |
270 const intx _threshold; | |
271 intx _ticks; | |
272 | |
273 public: | |
274 inline CMSLoopCountWarn(const char* src, const char* msg, | |
275 const intx threshold) : | |
276 _src(src), _msg(msg), _threshold(threshold), _ticks(0) { } | |
277 | |
278 inline void tick() { | |
279 _ticks++; | |
280 if (CMSLoopWarn && _ticks % _threshold == 0) { | |
281 warning("%s has looped %d times %s", _src, _ticks, _msg); | |
282 } | |
283 } | |
284 }; | |
1972 | 285 |
286 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP |