1 /*
2 * Copyright (c) 1997, 2014, 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.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/altHashing.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc_interface/collectedHeap.inline.hpp"
31 #include "memory/allocation.inline.hpp"
32 #include "memory/filemap.hpp"
33 #include "memory/gcLocker.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "oops/oop.inline2.hpp"
36 #include "runtime/mutexLocker.hpp"
37 #include "utilities/hashtable.inline.hpp"
38 #if INCLUDE_ALL_GCS
39 #include "gc_implementation/g1/g1StringDedup.hpp"
40 #endif
41
42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
43
44 // the number of buckets a thread claims
45 const int ClaimChunkSize = 32;
46
47 #ifdef ASSERT
48 class StableMemoryChecker : public StackObj {
49 enum { _bufsize = wordSize*4 };
50
51 address _region;
52 jint _size;
53 u1 _save_buf[_bufsize];
54
55 int sample(u1* save_buf) {
56 if (_size <= _bufsize) {
57 memcpy(save_buf, _region, _size);
58 return _size;
59 } else {
60 // copy head and tail
61 memcpy(&save_buf[0], _region, _bufsize/2);
62 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
63 return (_bufsize/2)*2;
64 }
65 }
66
67 public:
68 StableMemoryChecker(const void* region, jint size) {
69 _region = (address) region;
70 _size = size;
71 sample(_save_buf);
72 }
73
74 bool verify() {
75 u1 check_buf[sizeof(_save_buf)];
76 int check_size = sample(check_buf);
77 return (0 == memcmp(_save_buf, check_buf, check_size));
78 }
79
80 void set_region(const void* region) { _region = (address) region; }
81 };
82 #endif
83
84
85 // --------------------------------------------------------------------------
86 StringTable* StringTable::_the_table = NULL;
87
88 bool StringTable::_needs_rehashing = false;
89
90 volatile int StringTable::_parallel_claimed_idx = 0;
91
92 // Pick hashing algorithm
93 unsigned int StringTable::hash_string(const jchar* s, int len) {
94 return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
95 java_lang_String::hash_code(s, len);
96 }
97
98 oop StringTable::lookup(int index, jchar* name,
99 int len, unsigned int hash) {
100 int count = 0;
101 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
102 count++;
103 if (l->hash() == hash) {
104 if (java_lang_String::equals(l->literal(), name, len)) {
105 return l->literal();
106 }
107 }
108 }
109 // If the bucket size is too deep check if this hash code is insufficient.
110 if (count >= BasicHashtable<mtSymbol>::rehash_count && !needs_rehashing()) {
111 _needs_rehashing = check_rehash_table(count);
112 }
113 return NULL;
114 }
115
116
117 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
118 int len, unsigned int hashValue_arg, TRAPS) {
119
120 assert(java_lang_String::equals(string(), name, len),
121 "string must be properly initialized");
122 // Cannot hit a safepoint in this function because the "this" pointer can move.
123 No_Safepoint_Verifier nsv;
124
125 // Check if the symbol table has been rehashed, if so, need to recalculate
126 // the hash value and index before second lookup.
127 unsigned int hashValue;
128 int index;
129 if (use_alternate_hashcode()) {
130 hashValue = hash_string(name, len);
131 index = hash_to_index(hashValue);
132 } else {
133 hashValue = hashValue_arg;
134 index = index_arg;
135 }
136
137 // Since look-up was done lock-free, we need to check if another
138 // thread beat us in the race to insert the symbol.
139
140 oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
141 if (test != NULL) {
142 // Entry already added
143 return test;
144 }
145
146 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
147 add_entry(index, entry);
148 return string();
149 }
150
151
152 oop StringTable::lookup(Symbol* symbol) {
153 ResourceMark rm;
154 int length;
155 jchar* chars = symbol->as_unicode(length);
156 return lookup(chars, length);
157 }
158
159
160 oop StringTable::lookup(jchar* name, int len) {
161 unsigned int hash = hash_string(name, len);
162 int index = the_table()->hash_to_index(hash);
163 return the_table()->lookup(index, name, len, hash);
164 }
165
166
167 oop StringTable::intern(Handle string_or_null, jchar* name,
168 int len, TRAPS) {
169 unsigned int hashValue = hash_string(name, len);
170 int index = the_table()->hash_to_index(hashValue);
171 oop found_string = the_table()->lookup(index, name, len, hashValue);
172
173 // Found
174 if (found_string != NULL) return found_string;
175
176 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
177 assert(!Universe::heap()->is_in_reserved(name),
178 "proposed name of symbol must be stable");
179
180 Handle string;
181 // try to reuse the string if possible
182 if (!string_or_null.is_null()) {
183 string = string_or_null;
184 } else {
185 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
186 }
187
188 #if INCLUDE_ALL_GCS
189 if (G1StringDedup::is_enabled()) {
190 // Deduplicate the string before it is interned. Note that we should never
191 // deduplicate a string after it has been interned. Doing so will counteract
192 // compiler optimizations done on e.g. interned string literals.
193 G1StringDedup::deduplicate(string());
194 }
195 #endif
196
197 // Grab the StringTable_lock before getting the_table() because it could
198 // change at safepoint.
199 MutexLocker ml(StringTable_lock, THREAD);
200
201 // Otherwise, add to symbol to table
202 return the_table()->basic_add(index, string, name, len,
203 hashValue, CHECK_NULL);
204 }
205
206 oop StringTable::intern(Symbol* symbol, TRAPS) {
207 if (symbol == NULL) return NULL;
208 ResourceMark rm(THREAD);
209 int length;
210 jchar* chars = symbol->as_unicode(length);
211 Handle string;
212 oop result = intern(string, chars, length, CHECK_NULL);
213 return result;
214 }
215
216
217 oop StringTable::intern(oop string, TRAPS)
218 {
219 if (string == NULL) return NULL;
220 ResourceMark rm(THREAD);
221 int length;
222 Handle h_string (THREAD, string);
223 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
224 oop result = intern(h_string, chars, length, CHECK_NULL);
225 return result;
226 }
227
228
229 oop StringTable::intern(const char* utf8_string, TRAPS) {
230 if (utf8_string == NULL) return NULL;
231 ResourceMark rm(THREAD);
232 int length = UTF8::unicode_length(utf8_string);
233 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
234 UTF8::convert_to_unicode(utf8_string, chars, length);
235 Handle string;
236 oop result = intern(string, chars, length, CHECK_NULL);
237 return result;
238 }
239
240 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
241 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);
242 }
243
244 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
245 // Readers of the table are unlocked, so we should only be removing
246 // entries at a safepoint.
247 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
248 const int limit = the_table()->table_size();
249
250 for (;;) {
251 // Grab next set of buckets to scan
252 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
253 if (start_idx >= limit) {
254 // End of table
255 break;
256 }
257
258 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
259 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);
260 }
261 }
262
263 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
264 const int limit = the_table()->table_size();
265
266 assert(0 <= start_idx && start_idx <= limit,
267 err_msg("start_idx (%d) is out of bounds", start_idx));
268 assert(0 <= end_idx && end_idx <= limit,
269 err_msg("end_idx (%d) is out of bounds", end_idx));
270 assert(start_idx <= end_idx,
271 err_msg("Index ordering: start_idx=%d, end_idx=%d",
272 start_idx, end_idx));
273
274 for (int i = start_idx; i < end_idx; i += 1) {
275 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
276 while (entry != NULL) {
277 assert(!entry->is_shared(), "CDS not used for the StringTable");
278
279 f->do_oop((oop*)entry->literal_addr());
280
281 entry = entry->next();
282 }
283 }
284 }
285
286 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {
287 const int limit = the_table()->table_size();
288
289 assert(0 <= start_idx && start_idx <= limit,
290 err_msg("start_idx (%d) is out of bounds", start_idx));
291 assert(0 <= end_idx && end_idx <= limit,
292 err_msg("end_idx (%d) is out of bounds", end_idx));
293 assert(start_idx <= end_idx,
294 err_msg("Index ordering: start_idx=%d, end_idx=%d",
295 start_idx, end_idx));
296
297 for (int i = start_idx; i < end_idx; ++i) {
298 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
299 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
300 while (entry != NULL) {
301 assert(!entry->is_shared(), "CDS not used for the StringTable");
302
303 if (is_alive->do_object_b(entry->literal())) {
304 if (f != NULL) {
305 f->do_oop((oop*)entry->literal_addr());
306 }
307 p = entry->next_addr();
308 } else {
309 *p = entry->next();
310 the_table()->free_entry(entry);
311 (*removed)++;
312 }
313 (*processed)++;
314 entry = *p;
315 }
316 }
317 }
318
319 void StringTable::oops_do(OopClosure* f) {
320 buckets_oops_do(f, 0, the_table()->table_size());
321 }
322
323 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
324 const int limit = the_table()->table_size();
325
326 for (;;) {
327 // Grab next set of buckets to scan
328 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
329 if (start_idx >= limit) {
330 // End of table
331 break;
332 }
333
334 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
335 buckets_oops_do(f, start_idx, end_idx);
336 }
337 }
338
339 // This verification is part of Universe::verify() and needs to be quick.
340 // See StringTable::verify_and_compare() below for exhaustive verification.
341 void StringTable::verify() {
342 for (int i = 0; i < the_table()->table_size(); ++i) {
343 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
344 for ( ; p != NULL; p = p->next()) {
345 oop s = p->literal();
346 guarantee(s != NULL, "interned string is NULL");
347 unsigned int h = java_lang_String::hash_string(s);
348 guarantee(p->hash() == h, "broken hash in string table entry");
349 guarantee(the_table()->hash_to_index(h) == i,
350 "wrong index in string table");
351 }
352 }
353 }
354
355 void StringTable::dump(outputStream* st) {
356 the_table()->dump_table(st, "StringTable");
357 }
358
359 StringTable::VerifyRetTypes StringTable::compare_entries(
360 int bkt1, int e_cnt1,
361 HashtableEntry<oop, mtSymbol>* e_ptr1,
362 int bkt2, int e_cnt2,
363 HashtableEntry<oop, mtSymbol>* e_ptr2) {
364 // These entries are sanity checked by verify_and_compare_entries()
365 // before this function is called.
366 oop str1 = e_ptr1->literal();
367 oop str2 = e_ptr2->literal();
368
369 if (str1 == str2) {
370 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
371 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
372 (void *)str1, bkt1, e_cnt1, bkt2, e_cnt2);
373 return _verify_fail_continue;
374 }
375
376 if (java_lang_String::equals(str1, str2)) {
377 tty->print_cr("ERROR: identical String values in entry @ "
378 "bucket[%d][%d] and entry @ bucket[%d][%d]",
379 bkt1, e_cnt1, bkt2, e_cnt2);
380 return _verify_fail_continue;
381 }
382
383 return _verify_pass;
384 }
385
386 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
387 HashtableEntry<oop, mtSymbol>* e_ptr,
388 StringTable::VerifyMesgModes mesg_mode) {
389
390 VerifyRetTypes ret = _verify_pass; // be optimistic
391
392 oop str = e_ptr->literal();
393 if (str == NULL) {
394 if (mesg_mode == _verify_with_mesgs) {
395 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
396 e_cnt);
397 }
398 // NULL oop means no more verifications are possible
399 return _verify_fail_done;
400 }
401
402 if (str->klass() != SystemDictionary::String_klass()) {
403 if (mesg_mode == _verify_with_mesgs) {
404 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
405 bkt, e_cnt);
406 }
407 // not a String means no more verifications are possible
408 return _verify_fail_done;
409 }
410
411 unsigned int h = java_lang_String::hash_string(str);
412 if (e_ptr->hash() != h) {
413 if (mesg_mode == _verify_with_mesgs) {
414 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
415 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
416 }
417 ret = _verify_fail_continue;
418 }
419
420 if (the_table()->hash_to_index(h) != bkt) {
421 if (mesg_mode == _verify_with_mesgs) {
422 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
423 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
424 the_table()->hash_to_index(h));
425 }
426 ret = _verify_fail_continue;
427 }
428
429 return ret;
430 }
431
432 // See StringTable::verify() above for the quick verification that is
433 // part of Universe::verify(). This verification is exhaustive and
434 // reports on every issue that is found. StringTable::verify() only
435 // reports on the first issue that is found.
436 //
437 // StringTable::verify_entry() checks:
438 // - oop value != NULL (same as verify())
439 // - oop value is a String
440 // - hash(String) == hash in entry (same as verify())
441 // - index for hash == index of entry (same as verify())
442 //
443 // StringTable::compare_entries() checks:
444 // - oops are unique across all entries
445 // - String values are unique across all entries
446 //
447 int StringTable::verify_and_compare_entries() {
448 assert(StringTable_lock->is_locked(), "sanity check");
449
450 int fail_cnt = 0;
451
452 // first, verify all the entries individually:
453 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
454 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
455 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
456 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
457 if (ret != _verify_pass) {
458 fail_cnt++;
459 }
460 }
461 }
462
463 // Optimization: if the above check did not find any failures, then
464 // the comparison loop below does not need to call verify_entry()
465 // before calling compare_entries(). If there were failures, then we
466 // have to call verify_entry() to see if the entry can be passed to
467 // compare_entries() safely. When we call verify_entry() in the loop
468 // below, we do so quietly to void duplicate messages and we don't
469 // increment fail_cnt because the failures have already been counted.
470 bool need_entry_verify = (fail_cnt != 0);
471
472 // second, verify all entries relative to each other:
473 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
474 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
475 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
476 if (need_entry_verify) {
477 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
478 _verify_quietly);
479 if (ret == _verify_fail_done) {
480 // cannot use the current entry to compare against other entries
481 continue;
482 }
483 }
484
485 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
486 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
487 int e_cnt2;
488 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
489 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
490 // skip the entries up to and including the one that
491 // we're comparing against
492 continue;
493 }
494
495 if (need_entry_verify) {
496 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
497 _verify_quietly);
498 if (ret == _verify_fail_done) {
499 // cannot compare against this entry
500 continue;
501 }
502 }
503
504 // compare two entries, report and count any failures:
505 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
506 != _verify_pass) {
507 fail_cnt++;
508 }
509 }
510 }
511 }
512 }
513 return fail_cnt;
514 }
515
516 // Create a new table and using alternate hash code, populate the new table
517 // with the existing strings. Set flag to use the alternate hash code afterwards.
518 void StringTable::rehash_table() {
519 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
520 // This should never happen with -Xshare:dump but it might in testing mode.
521 if (DumpSharedSpaces) return;
522 StringTable* new_table = new StringTable();
523
524 // Rehash the table
525 the_table()->move_to(new_table);
526
527 // Delete the table and buckets (entries are reused in new table).
528 delete _the_table;
529 // Don't check if we need rehashing until the table gets unbalanced again.
530 // Then rehash with a new global seed.
531 _needs_rehashing = false;
532 _the_table = new_table;
533 }