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 "gc/shared/barrierSet.hpp"
31 #include "gc/shared/gcBehaviours.hpp"
32 #include "interpreter/bytecode.inline.hpp"
33 #include "logging/log.hpp"
34 #include "logging/logTag.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "oops/methodData.hpp"
37 #include "oops/method.inline.hpp"
38 #include "prims/methodHandles.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/mutexLocker.hpp"
41
42 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, const CodeBlobLayout& layout,
43 int frame_complete_offset, int frame_size, ImmutableOopMapSet* oop_maps,
44 bool caller_must_gc_arguments)
45 : CodeBlob(name, type, layout, frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
46 _mark_for_deoptimization_status(not_marked),
47 _is_unloading_state(0),
48 _method(method)
49 {
50 init_defaults();
51 clear_unloading_state();
52 }
53
54 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, int size,
55 int header_size, CodeBuffer* cb, int frame_complete_offset, int frame_size,
56 OopMapSet* oop_maps, bool caller_must_gc_arguments)
57 : CodeBlob(name, type, CodeBlobLayout((address) this, size, header_size, cb), cb,
58 frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
59 _mark_for_deoptimization_status(not_marked),
60 _is_unloading_state(0),
61 _method(method)
62 {
63 init_defaults();
64 clear_unloading_state();
65 }
66
67 void CompiledMethod::init_defaults() {
68 _has_unsafe_access = 0;
69 _has_method_handle_invokes = 0;
70 _lazy_critical_native = 0;
71 _has_wide_vectors = 0;
72 }
73
74 bool CompiledMethod::is_method_handle_return(address return_pc) {
75 if (!has_method_handle_invokes()) return false;
76 PcDesc* pd = pc_desc_at(return_pc);
77 if (pd == NULL)
78 return false;
79 return pd->is_method_handle_invoke();
80 }
81
82 // Returns a string version of the method state.
83 const char* CompiledMethod::state() const {
84 int state = get_state();
85 switch (state) {
86 case not_installed:
87 return "not installed";
88 case in_use:
89 return "in use";
90 case not_used:
91 return "not_used";
92 case not_entrant:
93 return "not_entrant";
94 case zombie:
95 return "zombie";
96 case unloaded:
97 return "unloaded";
98 default:
99 fatal("unexpected method state: %d", state);
100 return NULL;
101 }
102 }
103
104 //-----------------------------------------------------------------------------
105
106 ExceptionCache* CompiledMethod::exception_cache_acquire() const {
107 return OrderAccess::load_acquire(&_exception_cache);
108 }
109
110 void CompiledMethod::add_exception_cache_entry(ExceptionCache* new_entry) {
111 assert(ExceptionCache_lock->owned_by_self(),"Must hold the ExceptionCache_lock");
112 assert(new_entry != NULL,"Must be non null");
113 assert(new_entry->next() == NULL, "Must be null");
114
115 for (;;) {
116 ExceptionCache *ec = exception_cache();
117 if (ec != NULL) {
118 Klass* ex_klass = ec->exception_type();
119 if (!ex_klass->is_loader_alive()) {
120 // We must guarantee that entries are not inserted with new next pointer
121 // edges to ExceptionCache entries with dead klasses, due to bad interactions
122 // with concurrent ExceptionCache cleanup. Therefore, the inserts roll
123 // the head pointer forward to the first live ExceptionCache, so that the new
124 // next pointers always point at live ExceptionCaches, that are not removed due
125 // to concurrent ExceptionCache cleanup.
126 ExceptionCache* next = ec->next();
127 if (Atomic::cmpxchg(next, &_exception_cache, ec) == ec) {
128 CodeCache::release_exception_cache(ec);
129 }
130 continue;
131 }
132 ec = exception_cache();
133 if (ec != NULL) {
134 new_entry->set_next(ec);
135 }
136 }
137 if (Atomic::cmpxchg(new_entry, &_exception_cache, ec) == ec) {
138 return;
139 }
140 }
141 }
142
143 void CompiledMethod::clean_exception_cache() {
144 // For each nmethod, only a single thread may call this cleanup function
145 // at the same time, whether called in STW cleanup or concurrent cleanup.
146 // Note that if the GC is processing exception cache cleaning in a concurrent phase,
147 // then a single writer may contend with cleaning up the head pointer to the
148 // first ExceptionCache node that has a Klass* that is alive. That is fine,
149 // as long as there is no concurrent cleanup of next pointers from concurrent writers.
150 // And the concurrent writers do not clean up next pointers, only the head.
151 // Also note that concurent readers will walk through Klass* pointers that are not
152 // alive. That does not cause ABA problems, because Klass* is deleted after
153 // a handshake with all threads, after all stale ExceptionCaches have been
154 // unlinked. That is also when the CodeCache::exception_cache_purge_list()
155 // is deleted, with all ExceptionCache entries that were cleaned concurrently.
156 // That similarly implies that CAS operations on ExceptionCache entries do not
157 // suffer from ABA problems as unlinking and deletion is separated by a global
158 // handshake operation.
159 ExceptionCache* prev = NULL;
160 ExceptionCache* curr = exception_cache_acquire();
161
162 while (curr != NULL) {
163 ExceptionCache* next = curr->next();
164
165 if (!curr->exception_type()->is_loader_alive()) {
166 if (prev == NULL) {
167 // Try to clean head; this is contended by concurrent inserts, that
168 // both lazily clean the head, and insert entries at the head. If
169 // the CAS fails, the operation is restarted.
170 if (Atomic::cmpxchg(next, &_exception_cache, curr) != curr) {
171 prev = NULL;
172 curr = exception_cache_acquire();
173 continue;
174 }
175 } else {
176 // It is impossible to during cleanup connect the next pointer to
177 // an ExceptionCache that has not been published before a safepoint
178 // prior to the cleanup. Therefore, release is not required.
179 prev->set_next(next);
180 }
181 // prev stays the same.
182
183 CodeCache::release_exception_cache(curr);
184 } else {
185 prev = curr;
186 }
187
188 curr = next;
189 }
190 }
191
192 // public method for accessing the exception cache
193 // These are the public access methods.
194 address CompiledMethod::handler_for_exception_and_pc(Handle exception, address pc) {
195 // We never grab a lock to read the exception cache, so we may
196 // have false negatives. This is okay, as it can only happen during
197 // the first few exception lookups for a given nmethod.
198 ExceptionCache* ec = exception_cache_acquire();
199 while (ec != NULL) {
200 address ret_val;
201 if ((ret_val = ec->match(exception,pc)) != NULL) {
202 return ret_val;
203 }
204 ec = ec->next();
205 }
206 return NULL;
207 }
208
209 void CompiledMethod::add_handler_for_exception_and_pc(Handle exception, address pc, address handler) {
210 // There are potential race conditions during exception cache updates, so we
211 // must own the ExceptionCache_lock before doing ANY modifications. Because
212 // we don't lock during reads, it is possible to have several threads attempt
213 // to update the cache with the same data. We need to check for already inserted
214 // copies of the current data before adding it.
215
216 MutexLocker ml(ExceptionCache_lock);
217 ExceptionCache* target_entry = exception_cache_entry_for_exception(exception);
218
219 if (target_entry == NULL || !target_entry->add_address_and_handler(pc,handler)) {
220 target_entry = new ExceptionCache(exception,pc,handler);
221 add_exception_cache_entry(target_entry);
222 }
223 }
224
225 // private method for handling exception cache
226 // These methods are private, and used to manipulate the exception cache
227 // directly.
228 ExceptionCache* CompiledMethod::exception_cache_entry_for_exception(Handle exception) {
229 ExceptionCache* ec = exception_cache_acquire();
230 while (ec != NULL) {
231 if (ec->match_exception_with_space(exception)) {
232 return ec;
233 }
234 ec = ec->next();
235 }
236 return NULL;
237 }
238
239 //-------------end of code for ExceptionCache--------------
240
241 bool CompiledMethod::is_at_poll_return(address pc) {
242 RelocIterator iter(this, pc, pc+1);
243 while (iter.next()) {
244 if (iter.type() == relocInfo::poll_return_type)
245 return true;
246 }
247 return false;
248 }
249
250
251 bool CompiledMethod::is_at_poll_or_poll_return(address pc) {
252 RelocIterator iter(this, pc, pc+1);
253 while (iter.next()) {
254 relocInfo::relocType t = iter.type();
255 if (t == relocInfo::poll_return_type || t == relocInfo::poll_type)
256 return true;
257 }
258 return false;
259 }
260
261 void CompiledMethod::verify_oop_relocations() {
262 // Ensure sure that the code matches the current oop values
263 RelocIterator iter(this, NULL, NULL);
264 while (iter.next()) {
265 if (iter.type() == relocInfo::oop_type) {
266 oop_Relocation* reloc = iter.oop_reloc();
267 if (!reloc->oop_is_immediate()) {
268 reloc->verify_oop_relocation();
269 }
270 }
271 }
272 }
273
274
275 ScopeDesc* CompiledMethod::scope_desc_at(address pc) {
276 PcDesc* pd = pc_desc_at(pc);
277 guarantee(pd != NULL, "scope must be present");
278 return new ScopeDesc(this, pd->scope_decode_offset(),
279 pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
280 pd->return_oop());
281 }
282
283 ScopeDesc* CompiledMethod::scope_desc_near(address pc) {
284 PcDesc* pd = pc_desc_near(pc);
285 guarantee(pd != NULL, "scope must be present");
286 return new ScopeDesc(this, pd->scope_decode_offset(),
287 pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
288 pd->return_oop());
289 }
290
291 address CompiledMethod::oops_reloc_begin() const {
292 // If the method is not entrant or zombie then a JMP is plastered over the
293 // first few bytes. If an oop in the old code was there, that oop
294 // should not get GC'd. Skip the first few bytes of oops on
295 // not-entrant methods.
296 if (frame_complete_offset() != CodeOffsets::frame_never_safe &&
297 code_begin() + frame_complete_offset() >
298 verified_entry_point() + NativeJump::instruction_size)
299 {
300 // If we have a frame_complete_offset after the native jump, then there
301 // is no point trying to look for oops before that. This is a requirement
302 // for being allowed to scan oops concurrently.
303 return code_begin() + frame_complete_offset();
304 }
305
306 // It is not safe to read oops concurrently using entry barriers, if their
307 // location depend on whether the nmethod is entrant or not.
308 assert(BarrierSet::barrier_set()->barrier_set_nmethod() == NULL, "Not safe oop scan");
309
310 address low_boundary = verified_entry_point();
311 if (!is_in_use() && is_nmethod()) {
312 low_boundary += NativeJump::instruction_size;
313 // %%% Note: On SPARC we patch only a 4-byte trap, not a full NativeJump.
314 // This means that the low_boundary is going to be a little too high.
315 // This shouldn't matter, since oops of non-entrant methods are never used.
316 // In fact, why are we bothering to look at oops in a non-entrant method??
317 }
318 return low_boundary;
319 }
320
321 int CompiledMethod::verify_icholder_relocations() {
322 ResourceMark rm;
323 int count = 0;
324
325 RelocIterator iter(this);
326 while(iter.next()) {
327 if (iter.type() == relocInfo::virtual_call_type) {
328 if (CompiledIC::is_icholder_call_site(iter.virtual_call_reloc(), this)) {
329 CompiledIC *ic = CompiledIC_at(&iter);
330 if (TraceCompiledIC) {
331 tty->print("noticed icholder " INTPTR_FORMAT " ", p2i(ic->cached_icholder()));
332 ic->print();
333 }
334 assert(ic->cached_icholder() != NULL, "must be non-NULL");
335 count++;
336 }
337 }
338 }
339
340 return count;
341 }
342
343 // Method that knows how to preserve outgoing arguments at call. This method must be
344 // called with a frame corresponding to a Java invoke
345 void CompiledMethod::preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) {
346 if (method() != NULL && !method()->is_native()) {
347 address pc = fr.pc();
348 SimpleScopeDesc ssd(this, pc);
349 Bytecode_invoke call(ssd.method(), ssd.bci());
350 bool has_receiver = call.has_receiver();
351 bool has_appendix = call.has_appendix();
352 Symbol* signature = call.signature();
353
354 // The method attached by JIT-compilers should be used, if present.
355 // Bytecode can be inaccurate in such case.
356 Method* callee = attached_method_before_pc(pc);
357 if (callee != NULL) {
358 has_receiver = !(callee->access_flags().is_static());
359 has_appendix = false;
360 signature = callee->signature();
361 }
362
363 fr.oops_compiled_arguments_do(signature, has_receiver, has_appendix, reg_map, f);
364 }
365 }
366
367 Method* CompiledMethod::attached_method(address call_instr) {
368 assert(code_contains(call_instr), "not part of the nmethod");
369 RelocIterator iter(this, call_instr, call_instr + 1);
370 while (iter.next()) {
371 if (iter.addr() == call_instr) {
372 switch(iter.type()) {
373 case relocInfo::static_call_type: return iter.static_call_reloc()->method_value();
374 case relocInfo::opt_virtual_call_type: return iter.opt_virtual_call_reloc()->method_value();
375 case relocInfo::virtual_call_type: return iter.virtual_call_reloc()->method_value();
376 default: break;
377 }
378 }
379 }
380 return NULL; // not found
381 }
382
383 Method* CompiledMethod::attached_method_before_pc(address pc) {
384 if (NativeCall::is_call_before(pc)) {
385 NativeCall* ncall = nativeCall_before(pc);
386 return attached_method(ncall->instruction_address());
387 }
388 return NULL; // not a call
389 }
390
391 void CompiledMethod::clear_inline_caches() {
392 assert(SafepointSynchronize::is_at_safepoint(), "cleaning of IC's only allowed at safepoint");
393 if (is_zombie()) {
394 return;
395 }
396
397 RelocIterator iter(this);
398 while (iter.next()) {
399 iter.reloc()->clear_inline_cache();
400 }
401 }
402
403 // Clear ICStubs of all compiled ICs
404 void CompiledMethod::clear_ic_stubs() {
405 assert(CompiledICLocker::is_safe(this), "mt unsafe call");
406 ResourceMark rm;
407 RelocIterator iter(this);
408 while(iter.next()) {
409 if (iter.type() == relocInfo::virtual_call_type) {
410 CompiledIC* ic = CompiledIC_at(&iter);
411 ic->clear_ic_stub();
412 }
413 }
414 }
415
416 #ifdef ASSERT
417 // Check class_loader is alive for this bit of metadata.
418 static void check_class(Metadata* md) {
419 Klass* klass = NULL;
420 if (md->is_klass()) {
421 klass = ((Klass*)md);
422 } else if (md->is_method()) {
423 klass = ((Method*)md)->method_holder();
424 } else if (md->is_methodData()) {
425 klass = ((MethodData*)md)->method()->method_holder();
426 } else {
427 md->print();
428 ShouldNotReachHere();
429 }
430 assert(klass->is_loader_alive(), "must be alive");
431 }
432 #endif // ASSERT
433
434
435 void CompiledMethod::clean_ic_if_metadata_is_dead(CompiledIC *ic) {
436 if (ic->is_icholder_call()) {
437 // The only exception is compiledICHolder metdata which may
438 // yet be marked below. (We check this further below).
439 CompiledICHolder* cichk_metdata = ic->cached_icholder();
440
441 if (cichk_metdata->is_loader_alive()) {
442 return;
443 }
444 } else {
445 Metadata* ic_metdata = ic->cached_metadata();
446 if (ic_metdata != NULL) {
447 if (ic_metdata->is_klass()) {
448 if (((Klass*)ic_metdata)->is_loader_alive()) {
449 return;
450 }
451 } else if (ic_metdata->is_method()) {
452 Method* method = (Method*)ic_metdata;
453 assert(!method->is_old(), "old method should have been cleaned");
454 if (method->method_holder()->is_loader_alive()) {
455 return;
456 }
457 } else {
458 ShouldNotReachHere();
459 }
460 }
461 }
462
463 ic->set_to_clean();
464 }
465
466 // static_stub_Relocations may have dangling references to
467 // nmethods so trim them out here. Otherwise it looks like
468 // compiled code is maintaining a link to dead metadata.
469 void CompiledMethod::clean_ic_stubs() {
470 #ifdef ASSERT
471 address low_boundary = oops_reloc_begin();
472 RelocIterator iter(this, low_boundary);
473 while (iter.next()) {
474 address static_call_addr = NULL;
475 if (iter.type() == relocInfo::opt_virtual_call_type) {
476 CompiledIC* cic = CompiledIC_at(&iter);
477 if (!cic->is_call_to_interpreted()) {
478 static_call_addr = iter.addr();
479 }
480 } else if (iter.type() == relocInfo::static_call_type) {
481 CompiledStaticCall* csc = compiledStaticCall_at(iter.reloc());
482 if (!csc->is_call_to_interpreted()) {
483 static_call_addr = iter.addr();
484 }
485 }
486 if (static_call_addr != NULL) {
487 RelocIterator sciter(this, low_boundary);
488 while (sciter.next()) {
489 if (sciter.type() == relocInfo::static_stub_type &&
490 sciter.static_stub_reloc()->static_call() == static_call_addr) {
491 sciter.static_stub_reloc()->clear_inline_cache();
492 }
493 }
494 }
495 }
496 #endif
497 }
498
499 // Clean references to unloaded nmethods at addr from this one, which is not unloaded.
500 template <class CompiledICorStaticCall>
501 static void clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from,
502 bool clean_all) {
503 // Ok, to lookup references to zombies here
504 CodeBlob *cb = CodeCache::find_blob_unsafe(addr);
505 CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
506 if (nm != NULL) {
507 // Clean inline caches pointing to both zombie and not_entrant methods
508 if (clean_all || !nm->is_in_use() || nm->is_unloading() || (nm->method()->code() != nm)) {
509 ic->set_to_clean(from->is_alive());
510 assert(ic->is_clean(), "nmethod " PTR_FORMAT "not clean %s", p2i(from), from->method()->name_and_sig_as_C_string());
511 }
512 }
513 }
514
515 static void clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from,
516 bool clean_all) {
517 clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from, clean_all);
518 }
519
520 static void clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from,
521 bool clean_all) {
522 clean_if_nmethod_is_unloaded(csc, csc->destination(), from, clean_all);
523 }
524
525 // Cleans caches in nmethods that point to either classes that are unloaded
526 // or nmethods that are unloaded.
527 //
528 // Can be called either in parallel by G1 currently or after all
529 // nmethods are unloaded. Return postponed=true in the parallel case for
530 // inline caches found that point to nmethods that are not yet visited during
531 // the do_unloading walk.
532 void CompiledMethod::unload_nmethod_caches(bool unloading_occurred) {
533 ResourceMark rm;
534
535 // Exception cache only needs to be called if unloading occurred
536 if (unloading_occurred) {
537 clean_exception_cache();
538 }
539
540 cleanup_inline_caches_impl(unloading_occurred, false);
541
542 // All static stubs need to be cleaned.
543 clean_ic_stubs();
544
545 // Check that the metadata embedded in the nmethod is alive
546 DEBUG_ONLY(metadata_do(check_class));
547 }
548
549 // The _is_unloading_state encodes a tuple comprising the unloading cycle
550 // and the result of IsUnloadingBehaviour::is_unloading() fpr that cycle.
551 // This is the bit layout of the _is_unloading_state byte: 00000CCU
552 // CC refers to the cycle, which has 2 bits, and U refers to the result of
553 // IsUnloadingBehaviour::is_unloading() for that unloading cycle.
554
555 class IsUnloadingState: public AllStatic {
556 static const uint8_t _is_unloading_mask = 1;
557 static const uint8_t _is_unloading_shift = 0;
558 static const uint8_t _unloading_cycle_mask = 6;
559 static const uint8_t _unloading_cycle_shift = 1;
560
561 static uint8_t set_is_unloading(uint8_t state, bool value) {
562 state &= ~_is_unloading_mask;
563 if (value) {
564 state |= 1 << _is_unloading_shift;
565 }
566 assert(is_unloading(state) == value, "unexpected unloading cycle overflow");
567 return state;
568 }
569
570 static uint8_t set_unloading_cycle(uint8_t state, uint8_t value) {
571 state &= ~_unloading_cycle_mask;
572 state |= value << _unloading_cycle_shift;
573 assert(unloading_cycle(state) == value, "unexpected unloading cycle overflow");
574 return state;
575 }
576
577 public:
578 static bool is_unloading(uint8_t state) { return (state & _is_unloading_mask) >> _is_unloading_shift == 1; }
579 static uint8_t unloading_cycle(uint8_t state) { return (state & _unloading_cycle_mask) >> _unloading_cycle_shift; }
580
581 static uint8_t create(bool is_unloading, uint8_t unloading_cycle) {
582 uint8_t state = 0;
583 state = set_is_unloading(state, is_unloading);
584 state = set_unloading_cycle(state, unloading_cycle);
585 return state;
586 }
587 };
588
589 bool CompiledMethod::is_unloading() {
590 uint8_t state = RawAccess<MO_RELAXED>::load(&_is_unloading_state);
591 bool state_is_unloading = IsUnloadingState::is_unloading(state);
592 uint8_t state_unloading_cycle = IsUnloadingState::unloading_cycle(state);
593 if (state_is_unloading) {
594 return true;
595 }
596 if (state_unloading_cycle == CodeCache::unloading_cycle()) {
597 return false;
598 }
599
600 // The IsUnloadingBehaviour is responsible for checking if there are any dead
601 // oops in the CompiledMethod, by calling oops_do on it.
602 state_unloading_cycle = CodeCache::unloading_cycle();
603 state_is_unloading = IsUnloadingBehaviour::current()->is_unloading(this);
604
605 state = IsUnloadingState::create(state_is_unloading, state_unloading_cycle);
606
607 RawAccess<MO_RELAXED>::store(&_is_unloading_state, state);
608
609 return state_is_unloading;
610 }
611
612 void CompiledMethod::clear_unloading_state() {
613 uint8_t state = IsUnloadingState::create(false, CodeCache::unloading_cycle());
614 RawAccess<MO_RELAXED>::store(&_is_unloading_state, state);
615 }
616
617 // Called to clean up after class unloading for live nmethods and from the sweeper
618 // for all methods.
619 void CompiledMethod::cleanup_inline_caches_impl(bool unloading_occurred, bool clean_all) {
620 assert(CompiledICLocker::is_safe(this), "mt unsafe call");
621 ResourceMark rm;
622
623 // Find all calls in an nmethod and clear the ones that point to non-entrant,
624 // zombie and unloaded nmethods.
625 RelocIterator iter(this, oops_reloc_begin());
626 while(iter.next()) {
627
628 switch (iter.type()) {
629
630 case relocInfo::virtual_call_type:
631 if (unloading_occurred) {
632 // If class unloading occurred we first clear ICs where the cached metadata
633 // is referring to an unloaded klass or method.
634 clean_ic_if_metadata_is_dead(CompiledIC_at(&iter));
635 }
636
637 clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all);
638 break;
639
640 case relocInfo::opt_virtual_call_type:
641 clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all);
642 break;
643
644 case relocInfo::static_call_type:
645 clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, clean_all);
646 break;
647
648 case relocInfo::oop_type:
649 break;
650
651 case relocInfo::metadata_type:
652 break; // nothing to do.
653
654 default:
655 break;
656 }
657 }
658 }
659
660 // Iterating over all nmethods, e.g. with the help of CodeCache::nmethods_do(fun) was found
661 // to not be inherently safe. There is a chance that fields are seen which are not properly
662 // initialized. This happens despite the fact that nmethods_do() asserts the CodeCache_lock
663 // to be held.
664 // To bundle knowledge about necessary checks in one place, this function was introduced.
665 // It is not claimed that these checks are sufficient, but they were found to be necessary.
666 bool CompiledMethod::nmethod_access_is_safe(nmethod* nm) {
667 Method* method = (nm == NULL) ? NULL : nm->method(); // nm->method() may be uninitialized, i.e. != NULL, but invalid
668 return (nm != NULL) && (method != NULL) && (method->signature() != NULL) &&
669 !nm->is_zombie() && !nm->is_not_installed() &&
670 os::is_readable_pointer(method) &&
671 os::is_readable_pointer(method->constants()) &&
672 os::is_readable_pointer(method->signature());
673 }