1 /*
2 * Copyright (c) 2015, 2018, 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 "code/compiledIC.hpp"
27 #include "code/compiledMethod.inline.hpp"
28 #include "code/scopeDesc.hpp"
29 #include "code/codeCache.hpp"
30 #include "interpreter/bytecode.inline.hpp"
31 #include "logging/log.hpp"
32 #include "logging/logTag.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "oops/methodData.hpp"
35 #include "oops/method.inline.hpp"
36 #include "prims/methodHandles.hpp"
37 #include "runtime/handles.inline.hpp"
38 #include "runtime/mutexLocker.hpp"
39
40 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, const CodeBlobLayout& layout, int frame_complete_offset, int frame_size, ImmutableOopMapSet* oop_maps, bool caller_must_gc_arguments)
41 : CodeBlob(name, type, layout, frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
42 _mark_for_deoptimization_status(not_marked), _method(method) {
43 init_defaults();
44 }
45
46 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, int size, int header_size, CodeBuffer* cb, int frame_complete_offset, int frame_size, OopMapSet* oop_maps, bool caller_must_gc_arguments)
47 : CodeBlob(name, type, CodeBlobLayout((address) this, size, header_size, cb), cb, frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
48 _mark_for_deoptimization_status(not_marked), _method(method) {
49 init_defaults();
50 }
51
52 void CompiledMethod::init_defaults() {
53 _has_unsafe_access = 0;
54 _has_method_handle_invokes = 0;
55 _lazy_critical_native = 0;
56 _has_wide_vectors = 0;
57 _unloading_clock = 0;
58 }
59
60 bool CompiledMethod::is_method_handle_return(address return_pc) {
61 if (!has_method_handle_invokes()) return false;
62 PcDesc* pd = pc_desc_at(return_pc);
63 if (pd == NULL)
64 return false;
65 return pd->is_method_handle_invoke();
66 }
67
68 // Returns a string version of the method state.
69 const char* CompiledMethod::state() const {
70 int state = get_state();
71 switch (state) {
72 case not_installed:
73 return "not installed";
74 case in_use:
75 return "in use";
76 case not_used:
77 return "not_used";
78 case not_entrant:
79 return "not_entrant";
80 case zombie:
81 return "zombie";
82 case unloaded:
83 return "unloaded";
84 default:
85 fatal("unexpected method state: %d", state);
86 return NULL;
87 }
88 }
89
90 //-----------------------------------------------------------------------------
91
92 ExceptionCache* CompiledMethod::exception_cache_acquire() const {
93 return OrderAccess::load_acquire(&_exception_cache);
94 }
95
96 void CompiledMethod::add_exception_cache_entry(ExceptionCache* new_entry) {
97 assert(ExceptionCache_lock->owned_by_self(),"Must hold the ExceptionCache_lock");
98 assert(new_entry != NULL,"Must be non null");
99 assert(new_entry->next() == NULL, "Must be null");
100
101 for (;;) {
102 ExceptionCache *ec = exception_cache();
103 if (ec != NULL) {
104 Klass* ex_klass = ec->exception_type();
105 if (!ex_klass->is_loader_alive()) {
106 // We must guarantee that entries are not inserted with new next pointer
107 // edges to ExceptionCache entries with dead klasses, due to bad interactions
108 // with concurrent ExceptionCache cleanup. Therefore, the inserts roll
109 // the head pointer forward to the first live ExceptionCache, so that the new
110 // next pointers always point at live ExceptionCaches, that are not removed due
111 // to concurrent ExceptionCache cleanup.
112 ExceptionCache* next = ec->next();
113 if (Atomic::cmpxchg(next, &_exception_cache, ec) == ec) {
114 CodeCache::release_exception_cache(ec);
115 }
116 continue;
117 }
118 ec = exception_cache();
119 if (ec != NULL) {
120 new_entry->set_next(ec);
121 }
122 }
123 if (Atomic::cmpxchg(new_entry, &_exception_cache, ec) == ec) {
124 return;
125 }
126 }
127 }
128
129 void CompiledMethod::clean_exception_cache() {
130 // For each nmethod, only a single thread may call this cleanup function
131 // at the same time, whether called in STW cleanup or concurrent cleanup.
132 // Note that if the GC is processing exception cache cleaning in a concurrent phase,
133 // then a single writer may contend with cleaning up the head pointer to the
134 // first ExceptionCache node that has a Klass* that is alive. That is fine,
135 // as long as there is no concurrent cleanup of next pointers from concurrent writers.
136 // And the concurrent writers do not clean up next pointers, only the head.
137 // Also note that concurent readers will walk through Klass* pointers that are not
138 // alive. That does not cause ABA problems, because Klass* is deleted after
139 // a handshake with all threads, after all stale ExceptionCaches have been
140 // unlinked. That is also when the CodeCache::exception_cache_purge_list()
141 // is deleted, with all ExceptionCache entries that were cleaned concurrently.
142 // That similarly implies that CAS operations on ExceptionCache entries do not
143 // suffer from ABA problems as unlinking and deletion is separated by a global
144 // handshake operation.
145 ExceptionCache* prev = NULL;
146 ExceptionCache* curr = exception_cache_acquire();
147
148 while (curr != NULL) {
149 ExceptionCache* next = curr->next();
150
151 if (!curr->exception_type()->is_loader_alive()) {
152 if (prev == NULL) {
153 // Try to clean head; this is contended by concurrent inserts, that
154 // both lazily clean the head, and insert entries at the head. If
155 // the CAS fails, the operation is restarted.
156 if (Atomic::cmpxchg(next, &_exception_cache, curr) != curr) {
157 prev = NULL;
158 curr = exception_cache_acquire();
159 continue;
160 }
161 } else {
162 // It is impossible to during cleanup connect the next pointer to
163 // an ExceptionCache that has not been published before a safepoint
164 // prior to the cleanup. Therefore, release is not required.
165 prev->set_next(next);
166 }
167 // prev stays the same.
168
169 CodeCache::release_exception_cache(curr);
170 } else {
171 prev = curr;
172 }
173
174 curr = next;
175 }
176 }
177
178 // public method for accessing the exception cache
179 // These are the public access methods.
180 address CompiledMethod::handler_for_exception_and_pc(Handle exception, address pc) {
181 // We never grab a lock to read the exception cache, so we may
182 // have false negatives. This is okay, as it can only happen during
183 // the first few exception lookups for a given nmethod.
184 ExceptionCache* ec = exception_cache_acquire();
185 while (ec != NULL) {
186 address ret_val;
187 if ((ret_val = ec->match(exception,pc)) != NULL) {
188 return ret_val;
189 }
190 ec = ec->next();
191 }
192 return NULL;
193 }
194
195 void CompiledMethod::add_handler_for_exception_and_pc(Handle exception, address pc, address handler) {
196 // There are potential race conditions during exception cache updates, so we
197 // must own the ExceptionCache_lock before doing ANY modifications. Because
198 // we don't lock during reads, it is possible to have several threads attempt
199 // to update the cache with the same data. We need to check for already inserted
200 // copies of the current data before adding it.
201
202 MutexLocker ml(ExceptionCache_lock);
203 ExceptionCache* target_entry = exception_cache_entry_for_exception(exception);
204
205 if (target_entry == NULL || !target_entry->add_address_and_handler(pc,handler)) {
206 target_entry = new ExceptionCache(exception,pc,handler);
207 add_exception_cache_entry(target_entry);
208 }
209 }
210
211 // private method for handling exception cache
212 // These methods are private, and used to manipulate the exception cache
213 // directly.
214 ExceptionCache* CompiledMethod::exception_cache_entry_for_exception(Handle exception) {
215 ExceptionCache* ec = exception_cache_acquire();
216 while (ec != NULL) {
217 if (ec->match_exception_with_space(exception)) {
218 return ec;
219 }
220 ec = ec->next();
221 }
222 return NULL;
223 }
224
225 //-------------end of code for ExceptionCache--------------
226
227 bool CompiledMethod::is_at_poll_return(address pc) {
228 RelocIterator iter(this, pc, pc+1);
229 while (iter.next()) {
230 if (iter.type() == relocInfo::poll_return_type)
231 return true;
232 }
233 return false;
234 }
235
236
237 bool CompiledMethod::is_at_poll_or_poll_return(address pc) {
238 RelocIterator iter(this, pc, pc+1);
239 while (iter.next()) {
240 relocInfo::relocType t = iter.type();
241 if (t == relocInfo::poll_return_type || t == relocInfo::poll_type)
242 return true;
243 }
244 return false;
245 }
246
247 void CompiledMethod::verify_oop_relocations() {
248 // Ensure sure that the code matches the current oop values
249 RelocIterator iter(this, NULL, NULL);
250 while (iter.next()) {
251 if (iter.type() == relocInfo::oop_type) {
252 oop_Relocation* reloc = iter.oop_reloc();
253 if (!reloc->oop_is_immediate()) {
254 reloc->verify_oop_relocation();
255 }
256 }
257 }
258 }
259
260
261 ScopeDesc* CompiledMethod::scope_desc_at(address pc) {
262 PcDesc* pd = pc_desc_at(pc);
263 guarantee(pd != NULL, "scope must be present");
264 return new ScopeDesc(this, pd->scope_decode_offset(),
265 pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
266 pd->return_oop());
267 }
268
269 ScopeDesc* CompiledMethod::scope_desc_near(address pc) {
270 PcDesc* pd = pc_desc_near(pc);
271 guarantee(pd != NULL, "scope must be present");
272 return new ScopeDesc(this, pd->scope_decode_offset(),
273 pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
274 pd->return_oop());
275 }
276
277 address CompiledMethod::oops_reloc_begin() const {
278 // If the method is not entrant or zombie then a JMP is plastered over the
279 // first few bytes. If an oop in the old code was there, that oop
280 // should not get GC'd. Skip the first few bytes of oops on
281 // not-entrant methods.
282 address low_boundary = verified_entry_point();
283 if (!is_in_use() && is_nmethod()) {
284 low_boundary += NativeJump::instruction_size;
285 // %%% Note: On SPARC we patch only a 4-byte trap, not a full NativeJump.
286 // This means that the low_boundary is going to be a little too high.
287 // This shouldn't matter, since oops of non-entrant methods are never used.
288 // In fact, why are we bothering to look at oops in a non-entrant method??
289 }
290 return low_boundary;
291 }
292
293 int CompiledMethod::verify_icholder_relocations() {
294 ResourceMark rm;
295 int count = 0;
296
297 RelocIterator iter(this);
298 while(iter.next()) {
299 if (iter.type() == relocInfo::virtual_call_type) {
300 if (CompiledIC::is_icholder_call_site(iter.virtual_call_reloc(), this)) {
301 CompiledIC *ic = CompiledIC_at(&iter);
302 if (TraceCompiledIC) {
303 tty->print("noticed icholder " INTPTR_FORMAT " ", p2i(ic->cached_icholder()));
304 ic->print();
305 }
306 assert(ic->cached_icholder() != NULL, "must be non-NULL");
307 count++;
308 }
309 }
310 }
311
312 return count;
313 }
314
315 // Method that knows how to preserve outgoing arguments at call. This method must be
316 // called with a frame corresponding to a Java invoke
317 void CompiledMethod::preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) {
318 if (method() != NULL && !method()->is_native()) {
319 address pc = fr.pc();
320 SimpleScopeDesc ssd(this, pc);
321 Bytecode_invoke call(ssd.method(), ssd.bci());
322 bool has_receiver = call.has_receiver();
323 bool has_appendix = call.has_appendix();
324 Symbol* signature = call.signature();
325
326 // The method attached by JIT-compilers should be used, if present.
327 // Bytecode can be inaccurate in such case.
328 Method* callee = attached_method_before_pc(pc);
329 if (callee != NULL) {
330 has_receiver = !(callee->access_flags().is_static());
331 has_appendix = false;
332 signature = callee->signature();
333 }
334
335 fr.oops_compiled_arguments_do(signature, has_receiver, has_appendix, reg_map, f);
336 }
337 }
338
339 Method* CompiledMethod::attached_method(address call_instr) {
340 assert(code_contains(call_instr), "not part of the nmethod");
341 RelocIterator iter(this, call_instr, call_instr + 1);
342 while (iter.next()) {
343 if (iter.addr() == call_instr) {
344 switch(iter.type()) {
345 case relocInfo::static_call_type: return iter.static_call_reloc()->method_value();
346 case relocInfo::opt_virtual_call_type: return iter.opt_virtual_call_reloc()->method_value();
347 case relocInfo::virtual_call_type: return iter.virtual_call_reloc()->method_value();
348 default: break;
349 }
350 }
351 }
352 return NULL; // not found
353 }
354
355 Method* CompiledMethod::attached_method_before_pc(address pc) {
356 if (NativeCall::is_call_before(pc)) {
357 NativeCall* ncall = nativeCall_before(pc);
358 return attached_method(ncall->instruction_address());
359 }
360 return NULL; // not a call
361 }
362
363 void CompiledMethod::clear_inline_caches() {
364 assert(SafepointSynchronize::is_at_safepoint(), "cleaning of IC's only allowed at safepoint");
365 if (is_zombie()) {
366 return;
367 }
368
369 RelocIterator iter(this);
370 while (iter.next()) {
371 iter.reloc()->clear_inline_cache();
372 }
373 }
374
375 // Clear ICStubs of all compiled ICs
376 void CompiledMethod::clear_ic_stubs() {
377 assert_locked_or_safepoint(CompiledIC_lock);
378 ResourceMark rm;
379 RelocIterator iter(this);
380 while(iter.next()) {
381 if (iter.type() == relocInfo::virtual_call_type) {
382 CompiledIC* ic = CompiledIC_at(&iter);
383 ic->clear_ic_stub();
384 }
385 }
386 }
387
388 #ifdef ASSERT
389 // Check class_loader is alive for this bit of metadata.
390 static void check_class(Metadata* md) {
391 Klass* klass = NULL;
392 if (md->is_klass()) {
393 klass = ((Klass*)md);
394 } else if (md->is_method()) {
395 klass = ((Method*)md)->method_holder();
396 } else if (md->is_methodData()) {
397 klass = ((MethodData*)md)->method()->method_holder();
398 } else {
399 md->print();
400 ShouldNotReachHere();
401 }
402 assert(klass->is_loader_alive(), "must be alive");
403 }
404 #endif // ASSERT
405
406
407 void CompiledMethod::clean_ic_if_metadata_is_dead(CompiledIC *ic) {
408 if (ic->is_icholder_call()) {
409 // The only exception is compiledICHolder metdata which may
410 // yet be marked below. (We check this further below).
411 CompiledICHolder* cichk_metdata = ic->cached_icholder();
412
413 if (cichk_metdata->is_loader_alive()) {
414 return;
415 }
416 } else {
417 Metadata* ic_metdata = ic->cached_metadata();
418 if (ic_metdata != NULL) {
419 if (ic_metdata->is_klass()) {
420 if (((Klass*)ic_metdata)->is_loader_alive()) {
421 return;
422 }
423 } else if (ic_metdata->is_method()) {
424 Method* method = (Method*)ic_metdata;
425 assert(!method->is_old(), "old method should have been cleaned");
426 if (method->method_holder()->is_loader_alive()) {
427 return;
428 }
429 } else {
430 ShouldNotReachHere();
431 }
432 }
433 }
434
435 ic->set_to_clean();
436 }
437
438 unsigned char CompiledMethod::_global_unloading_clock = 0;
439
440 void CompiledMethod::increase_unloading_clock() {
441 _global_unloading_clock++;
442 if (_global_unloading_clock == 0) {
443 // _nmethods are allocated with _unloading_clock == 0,
444 // so 0 is never used as a clock value.
445 _global_unloading_clock = 1;
446 }
447 }
448
449 void CompiledMethod::set_unloading_clock(unsigned char unloading_clock) {
450 OrderAccess::release_store(&_unloading_clock, unloading_clock);
451 }
452
453 unsigned char CompiledMethod::unloading_clock() {
454 return OrderAccess::load_acquire(&_unloading_clock);
455 }
456
457
458 // static_stub_Relocations may have dangling references to
459 // nmethods so trim them out here. Otherwise it looks like
460 // compiled code is maintaining a link to dead metadata.
461 void CompiledMethod::clean_ic_stubs() {
462 #ifdef ASSERT
463 address low_boundary = oops_reloc_begin();
464 RelocIterator iter(this, low_boundary);
465 while (iter.next()) {
466 address static_call_addr = NULL;
467 if (iter.type() == relocInfo::opt_virtual_call_type) {
468 CompiledIC* cic = CompiledIC_at(&iter);
469 if (!cic->is_call_to_interpreted()) {
470 static_call_addr = iter.addr();
471 }
472 } else if (iter.type() == relocInfo::static_call_type) {
473 CompiledStaticCall* csc = compiledStaticCall_at(iter.reloc());
474 if (!csc->is_call_to_interpreted()) {
475 static_call_addr = iter.addr();
476 }
477 }
478 if (static_call_addr != NULL) {
479 RelocIterator sciter(this, low_boundary);
480 while (sciter.next()) {
481 if (sciter.type() == relocInfo::static_stub_type &&
482 sciter.static_stub_reloc()->static_call() == static_call_addr) {
483 sciter.static_stub_reloc()->clear_inline_cache();
484 }
485 }
486 }
487 }
488 #endif
489 }
490
491 // This is called at the end of the strong tracing/marking phase of a
492 // GC to unload an nmethod if it contains otherwise unreachable
493 // oops.
494
495 void CompiledMethod::do_unloading(BoolObjectClosure* is_alive) {
496 // Make sure the oop's ready to receive visitors
497 assert(!is_zombie() && !is_unloaded(),
498 "should not call follow on zombie or unloaded nmethod");
499
500 address low_boundary = oops_reloc_begin();
501
502 if (do_unloading_oops(low_boundary, is_alive)) {
503 return;
504 }
505
506 #if INCLUDE_JVMCI
507 if (do_unloading_jvmci()) {
508 return;
509 }
510 #endif
511
512 // Cleanup exception cache and inline caches happens
513 // after all the unloaded methods are found.
514 }
515
516 // Clean references to unloaded nmethods at addr from this one, which is not unloaded.
517 template <class CompiledICorStaticCall>
518 static bool clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from,
519 bool parallel, bool clean_all) {
520 // Ok, to lookup references to zombies here
521 CodeBlob *cb = CodeCache::find_blob_unsafe(addr);
522 CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
523 if (nm != NULL) {
524 if (parallel && nm->unloading_clock() != CompiledMethod::global_unloading_clock()) {
525 // The nmethod has not been processed yet.
526 return true;
527 }
528
529 // Clean inline caches pointing to both zombie and not_entrant methods
530 if (clean_all || !nm->is_in_use() || (nm->method()->code() != nm)) {
531 ic->set_to_clean(from->is_alive());
532 assert(ic->is_clean(), "nmethod " PTR_FORMAT "not clean %s", p2i(from), from->method()->name_and_sig_as_C_string());
533 }
534 }
535
536 return false;
537 }
538
539 static bool clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from,
540 bool parallel, bool clean_all = false) {
541 return clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from, parallel, clean_all);
542 }
543
544 static bool clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from,
545 bool parallel, bool clean_all = false) {
546 return clean_if_nmethod_is_unloaded(csc, csc->destination(), from, parallel, clean_all);
547 }
548
549 bool CompiledMethod::do_unloading_parallel(BoolObjectClosure* is_alive, bool unloading_occurred) {
550 ResourceMark rm;
551
552 // Make sure the oop's ready to receive visitors
553 assert(!is_zombie() && !is_unloaded(),
554 "should not call follow on zombie or unloaded nmethod");
555
556 address low_boundary = oops_reloc_begin();
557
558 if (do_unloading_oops(low_boundary, is_alive)) {
559 return false;
560 }
561
562 #if INCLUDE_JVMCI
563 if (do_unloading_jvmci()) {
564 return false;
565 }
566 #endif
567
568 return unload_nmethod_caches(/*parallel*/true, unloading_occurred);
569 }
570
571 // Cleans caches in nmethods that point to either classes that are unloaded
572 // or nmethods that are unloaded.
573 //
574 // Can be called either in parallel by G1 currently or after all
575 // nmethods are unloaded. Return postponed=true in the parallel case for
576 // inline caches found that point to nmethods that are not yet visited during
577 // the do_unloading walk.
578 bool CompiledMethod::unload_nmethod_caches(bool parallel, bool unloading_occurred) {
579
580 // Exception cache only needs to be called if unloading occurred
581 if (unloading_occurred) {
582 clean_exception_cache();
583 }
584
585 bool postponed = cleanup_inline_caches_impl(parallel, unloading_occurred, /*clean_all*/false);
586
587 // All static stubs need to be cleaned.
588 clean_ic_stubs();
589
590 // Check that the metadata embedded in the nmethod is alive
591 DEBUG_ONLY(metadata_do(check_class));
592
593 return postponed;
594 }
595
596 // Called to clean up after class unloading for live nmethods and from the sweeper
597 // for all methods.
598 bool CompiledMethod::cleanup_inline_caches_impl(bool parallel, bool unloading_occurred, bool clean_all) {
599 assert_locked_or_safepoint(CompiledIC_lock);
600 bool postponed = false;
601 ResourceMark rm;
602
603 // Find all calls in an nmethod and clear the ones that point to non-entrant,
604 // zombie and unloaded nmethods.
605 RelocIterator iter(this, oops_reloc_begin());
606 while(iter.next()) {
607
608 switch (iter.type()) {
609
610 case relocInfo::virtual_call_type:
611 if (unloading_occurred) {
612 // If class unloading occurred we first clear ICs where the cached metadata
613 // is referring to an unloaded klass or method.
614 clean_ic_if_metadata_is_dead(CompiledIC_at(&iter));
615 }
616
617 postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, parallel, clean_all);
618 break;
619
620 case relocInfo::opt_virtual_call_type:
621 postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, parallel, clean_all);
622 break;
623
624 case relocInfo::static_call_type:
625 postponed |= clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, parallel, clean_all);
626 break;
627
628 case relocInfo::oop_type:
629 // handled by do_unloading_oops already
630 break;
631
632 case relocInfo::metadata_type:
633 break; // nothing to do.
634
635 default:
636 break;
637 }
638 }
639
640 return postponed;
641 }
642
643 void CompiledMethod::do_unloading_parallel_postponed() {
644 ResourceMark rm;
645
646 // Make sure the oop's ready to receive visitors
647 assert(!is_zombie(),
648 "should not call follow on zombie nmethod");
649
650 RelocIterator iter(this, oops_reloc_begin());
651 while(iter.next()) {
652
653 switch (iter.type()) {
654
655 case relocInfo::virtual_call_type:
656 clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, true);
657 break;
658
659 case relocInfo::opt_virtual_call_type:
660 clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, true);
661 break;
662
663 case relocInfo::static_call_type:
664 clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, true);
665 break;
666
667 default:
668 break;
669 }
670 }
671 }
672
673 // Iterating over all nmethods, e.g. with the help of CodeCache::nmethods_do(fun) was found
674 // to not be inherently safe. There is a chance that fields are seen which are not properly
675 // initialized. This happens despite the fact that nmethods_do() asserts the CodeCache_lock
676 // to be held.
677 // To bundle knowledge about necessary checks in one place, this function was introduced.
678 // It is not claimed that these checks are sufficient, but they were found to be necessary.
679 bool CompiledMethod::nmethod_access_is_safe(nmethod* nm) {
680 Method* method = (nm == NULL) ? NULL : nm->method(); // nm->method() may be uninitialized, i.e. != NULL, but invalid
681 return (nm != NULL) && (method != NULL) && (method->signature() != NULL) &&
682 !nm->is_zombie() && !nm->is_not_installed() &&
683 os::is_readable_pointer(method) &&
684 os::is_readable_pointer(method->constants()) &&
685 os::is_readable_pointer(method->signature());
686 }