1/* 2 * Copyright (c) 1997, 2016, 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#ifndef SHARE_VM_CODE_NMETHOD_HPP 26#define SHARE_VM_CODE_NMETHOD_HPP 27 28#include "code/compiledMethod.hpp" 29 30class DepChange; 31class DirectiveSet; 32 33// nmethods (native methods) are the compiled code versions of Java methods. 34// 35// An nmethod contains: 36// - header (the nmethod structure) 37// [Relocation] 38// - relocation information 39// - constant part (doubles, longs and floats used in nmethod) 40// - oop table 41// [Code] 42// - code body 43// - exception handler 44// - stub code 45// [Debugging information] 46// - oop array 47// - data array 48// - pcs 49// [Exception handler table] 50// - handler entry point array 51// [Implicit Null Pointer exception table] 52// - implicit null table array 53 54class nmethod : public CompiledMethod { 55 friend class VMStructs; 56 friend class JVMCIVMStructs; 57 friend class NMethodSweeper; 58 friend class CodeCache; // scavengable oops 59 private: 60 61 // Shared fields for all nmethod's 62 int _entry_bci; // != InvocationEntryBci if this nmethod is an on-stack replacement method 63 jmethodID _jmethod_id; // Cache of method()->jmethod_id() 64 65#if INCLUDE_JVMCI 66 // Needed to keep nmethods alive that are not the default nmethod for the associated Method. 67 oop _jvmci_installed_code; 68 oop _speculation_log; 69#endif 70 71 // To support simple linked-list chaining of nmethods: 72 nmethod* _osr_link; // from InstanceKlass::osr_nmethods_head 73 74 static nmethod* volatile _oops_do_mark_nmethods; 75 nmethod* volatile _oops_do_mark_link; 76 77 // offsets for entry points 78 address _entry_point; // entry point with class check 79 address _verified_entry_point; // entry point without class check 80 address _osr_entry_point; // entry point for on stack replacement 81 82 // Offsets for different nmethod parts 83 int _exception_offset; 84 // Offset of the unwind handler if it exists 85 int _unwind_handler_offset; 86 87 int _consts_offset; 88 int _stub_offset; 89 int _oops_offset; // offset to where embedded oop table begins (inside data) 90 int _metadata_offset; // embedded meta data table 91 int _scopes_data_offset; 92 int _scopes_pcs_offset; 93 int _dependencies_offset; 94 int _handler_table_offset; 95 int _nul_chk_table_offset; 96 int _nmethod_end_offset; 97 98 int code_offset() const { return (address) code_begin() - header_begin(); } 99 100 // location in frame (offset for sp) that deopt can store the original 101 // pc during a deopt. 102 int _orig_pc_offset; 103 104 int _compile_id; // which compilation made this nmethod 105 int _comp_level; // compilation level 106 107 // protected by CodeCache_lock 108 bool _has_flushed_dependencies; // Used for maintenance of dependencies (CodeCache_lock) 109 110 // used by jvmti to track if an unload event has been posted for this nmethod. 111 bool _unload_reported; 112 113 // Protected by Patching_lock 114 volatile unsigned char _state; // {in_use, not_entrant, zombie, unloaded} 115 116#ifdef ASSERT 117 bool _oops_are_stale; // indicates that it's no longer safe to access oops section 118#endif 119 120 jbyte _scavenge_root_state; 121 122#if INCLUDE_RTM_OPT 123 // RTM state at compile time. Used during deoptimization to decide 124 // whether to restart collecting RTM locking abort statistic again. 125 RTMState _rtm_state; 126#endif 127 128 // Nmethod Flushing lock. If non-zero, then the nmethod is not removed 129 // and is not made into a zombie. However, once the nmethod is made into 130 // a zombie, it will be locked one final time if CompiledMethodUnload 131 // event processing needs to be done. 132 volatile jint _lock_count; 133 134 // not_entrant method removal. Each mark_sweep pass will update 135 // this mark to current sweep invocation count if it is seen on the 136 // stack. An not_entrant method can be removed when there are no 137 // more activations, i.e., when the _stack_traversal_mark is less than 138 // current sweep traversal index. 139 long _stack_traversal_mark; 140 141 // The _hotness_counter indicates the hotness of a method. The higher 142 // the value the hotter the method. The hotness counter of a nmethod is 143 // set to [(ReservedCodeCacheSize / (1024 * 1024)) * 2] each time the method 144 // is active while stack scanning (mark_active_nmethods()). The hotness 145 // counter is decreased (by 1) while sweeping. 146 int _hotness_counter; 147 148 // These are used for compiled synchronized native methods to 149 // locate the owner and stack slot for the BasicLock so that we can 150 // properly revoke the bias of the owner if necessary. They are 151 // needed because there is no debug information for compiled native 152 // wrappers and the oop maps are insufficient to allow 153 // frame::retrieve_receiver() to work. Currently they are expected 154 // to be byte offsets from the Java stack pointer for maximum code 155 // sharing between platforms. Note that currently biased locking 156 // will never cause Class instances to be biased but this code 157 // handles the static synchronized case as well. 158 // JVMTI's GetLocalInstance() also uses these offsets to find the receiver 159 // for non-static native wrapper frames. 160 ByteSize _native_receiver_sp_offset; 161 ByteSize _native_basic_lock_sp_offset; 162 163 friend class nmethodLocker; 164 165 // For native wrappers 166 nmethod(Method* method, 167 CompilerType type, 168 int nmethod_size, 169 int compile_id, 170 CodeOffsets* offsets, 171 CodeBuffer *code_buffer, 172 int frame_size, 173 ByteSize basic_lock_owner_sp_offset, /* synchronized natives only */ 174 ByteSize basic_lock_sp_offset, /* synchronized natives only */ 175 OopMapSet* oop_maps); 176 177 // Creation support 178 nmethod(Method* method, 179 CompilerType type, 180 int nmethod_size, 181 int compile_id, 182 int entry_bci, 183 CodeOffsets* offsets, 184 int orig_pc_offset, 185 DebugInformationRecorder *recorder, 186 Dependencies* dependencies, 187 CodeBuffer *code_buffer, 188 int frame_size, 189 OopMapSet* oop_maps, 190 ExceptionHandlerTable* handler_table, 191 ImplicitExceptionTable* nul_chk_table, 192 AbstractCompiler* compiler, 193 int comp_level 194#if INCLUDE_JVMCI 195 , Handle installed_code, 196 Handle speculation_log 197#endif 198 ); 199 200 // helper methods 201 void* operator new(size_t size, int nmethod_size, int comp_level) throw(); 202 203 const char* reloc_string_for(u_char* begin, u_char* end); 204 // Returns true if this thread changed the state of the nmethod or 205 // false if another thread performed the transition. 206 bool make_not_entrant_or_zombie(unsigned int state); 207 bool make_entrant() { Unimplemented(); return false; } 208 void inc_decompile_count(); 209 210 // Inform external interfaces that a compiled method has been unloaded 211 void post_compiled_method_unload(); 212 213 // Initailize fields to their default values 214 void init_defaults(); 215 216 // Offsets 217 int content_offset() const { return content_begin() - header_begin(); } 218 int data_offset() const { return _data_offset; } 219 220 address header_end() const { return (address) header_begin() + header_size(); } 221 222 public: 223 // create nmethod with entry_bci 224 static nmethod* new_nmethod(const methodHandle& method, 225 int compile_id, 226 int entry_bci, 227 CodeOffsets* offsets, 228 int orig_pc_offset, 229 DebugInformationRecorder* recorder, 230 Dependencies* dependencies, 231 CodeBuffer *code_buffer, 232 int frame_size, 233 OopMapSet* oop_maps, 234 ExceptionHandlerTable* handler_table, 235 ImplicitExceptionTable* nul_chk_table, 236 AbstractCompiler* compiler, 237 int comp_level 238#if INCLUDE_JVMCI 239 , Handle installed_code = Handle(), 240 Handle speculation_log = Handle() 241#endif 242 ); 243 244 static nmethod* new_native_nmethod(const methodHandle& method, 245 int compile_id, 246 CodeBuffer *code_buffer, 247 int vep_offset, 248 int frame_complete, 249 int frame_size, 250 ByteSize receiver_sp_offset, 251 ByteSize basic_lock_sp_offset, 252 OopMapSet* oop_maps); 253 254 // type info 255 bool is_nmethod() const { return true; } 256 bool is_osr_method() const { return _entry_bci != InvocationEntryBci; } 257 258 // boundaries for different parts 259 address consts_begin () const { return header_begin() + _consts_offset ; } 260 address consts_end () const { return code_begin() ; } 261 address stub_begin () const { return header_begin() + _stub_offset ; } 262 address stub_end () const { return header_begin() + _oops_offset ; } 263 address exception_begin () const { return header_begin() + _exception_offset ; } 264 address unwind_handler_begin () const { return _unwind_handler_offset != -1 ? (header_begin() + _unwind_handler_offset) : NULL; } 265 oop* oops_begin () const { return (oop*) (header_begin() + _oops_offset) ; } 266 oop* oops_end () const { return (oop*) (header_begin() + _metadata_offset) ; } 267 268 Metadata** metadata_begin () const { return (Metadata**) (header_begin() + _metadata_offset) ; } 269 Metadata** metadata_end () const { return (Metadata**) _scopes_data_begin; } 270 271 address scopes_data_end () const { return header_begin() + _scopes_pcs_offset ; } 272 PcDesc* scopes_pcs_begin () const { return (PcDesc*)(header_begin() + _scopes_pcs_offset ); } 273 PcDesc* scopes_pcs_end () const { return (PcDesc*)(header_begin() + _dependencies_offset) ; } 274 address dependencies_begin () const { return header_begin() + _dependencies_offset ; } 275 address dependencies_end () const { return header_begin() + _handler_table_offset ; } 276 address handler_table_begin () const { return header_begin() + _handler_table_offset ; } 277 address handler_table_end () const { return header_begin() + _nul_chk_table_offset ; } 278 address nul_chk_table_begin () const { return header_begin() + _nul_chk_table_offset ; } 279 address nul_chk_table_end () const { return header_begin() + _nmethod_end_offset ; } 280 281 // Sizes 282 int oops_size () const { return (address) oops_end () - (address) oops_begin (); } 283 int metadata_size () const { return (address) metadata_end () - (address) metadata_begin (); } 284 int dependencies_size () const { return dependencies_end () - dependencies_begin (); } 285 286 int oops_count() const { assert(oops_size() % oopSize == 0, ""); return (oops_size() / oopSize) + 1; } 287 int metadata_count() const { assert(metadata_size() % wordSize == 0, ""); return (metadata_size() / wordSize) + 1; } 288 289 int total_size () const; 290 291 void dec_hotness_counter() { _hotness_counter--; } 292 void set_hotness_counter(int val) { _hotness_counter = val; } 293 int hotness_counter() const { return _hotness_counter; } 294 295 // Containment 296 bool oops_contains (oop* addr) const { return oops_begin () <= addr && addr < oops_end (); } 297 bool metadata_contains (Metadata** addr) const { return metadata_begin () <= addr && addr < metadata_end (); } 298 bool scopes_data_contains (address addr) const { return scopes_data_begin () <= addr && addr < scopes_data_end (); } 299 bool scopes_pcs_contains (PcDesc* addr) const { return scopes_pcs_begin () <= addr && addr < scopes_pcs_end (); } 300 301 // entry points 302 address entry_point() const { return _entry_point; } // normal entry point 303 address verified_entry_point() const { return _verified_entry_point; } // if klass is correct 304 305 // flag accessing and manipulation 306 bool is_in_use() const { return _state == in_use; } 307 bool is_alive() const { unsigned char s = _state; return s < zombie; } 308 bool is_not_entrant() const { return _state == not_entrant; } 309 bool is_zombie() const { return _state == zombie; } 310 bool is_unloaded() const { return _state == unloaded; } 311 312#if INCLUDE_RTM_OPT 313 // rtm state accessing and manipulating 314 RTMState rtm_state() const { return _rtm_state; } 315 void set_rtm_state(RTMState state) { _rtm_state = state; } 316#endif 317 318 // Make the nmethod non entrant. The nmethod will continue to be 319 // alive. It is used when an uncommon trap happens. Returns true 320 // if this thread changed the state of the nmethod or false if 321 // another thread performed the transition. 322 bool make_not_entrant() { 323 assert(!method()->is_method_handle_intrinsic(), "Cannot make MH intrinsic not entrant"); 324 return make_not_entrant_or_zombie(not_entrant); 325 } 326 bool make_not_used() { return make_not_entrant(); } 327 bool make_zombie() { return make_not_entrant_or_zombie(zombie); } 328 329 // used by jvmti to track if the unload event has been reported 330 bool unload_reported() { return _unload_reported; } 331 void set_unload_reported() { _unload_reported = true; } 332 333 int get_state() const { 334 return _state; 335 } 336 337 void make_unloaded(BoolObjectClosure* is_alive, oop cause); 338 339 bool has_dependencies() { return dependencies_size() != 0; } 340 void flush_dependencies(BoolObjectClosure* is_alive); 341 bool has_flushed_dependencies() { return _has_flushed_dependencies; } 342 void set_has_flushed_dependencies() { 343 assert(!has_flushed_dependencies(), "should only happen once"); 344 _has_flushed_dependencies = 1; 345 } 346 347 int comp_level() const { return _comp_level; } 348 349 // Support for oops in scopes and relocs: 350 // Note: index 0 is reserved for null. 351 oop oop_at(int index) const { return index == 0 ? (oop) NULL: *oop_addr_at(index); } 352 oop* oop_addr_at(int index) const { // for GC 353 // relocation indexes are biased by 1 (because 0 is reserved) 354 assert(index > 0 && index <= oops_count(), "must be a valid non-zero index"); 355 assert(!_oops_are_stale, "oops are stale"); 356 return &oops_begin()[index - 1]; 357 } 358 359 // Support for meta data in scopes and relocs: 360 // Note: index 0 is reserved for null. 361 Metadata* metadata_at(int index) const { return index == 0 ? NULL: *metadata_addr_at(index); } 362 Metadata** metadata_addr_at(int index) const { // for GC 363 // relocation indexes are biased by 1 (because 0 is reserved) 364 assert(index > 0 && index <= metadata_count(), "must be a valid non-zero index"); 365 return &metadata_begin()[index - 1]; 366 } 367 368 void copy_values(GrowableArray<jobject>* oops); 369 void copy_values(GrowableArray<Metadata*>* metadata); 370 371 // Relocation support 372private: 373 void fix_oop_relocations(address begin, address end, bool initialize_immediates); 374 inline void initialize_immediate_oop(oop* dest, jobject handle); 375 376public: 377 void fix_oop_relocations(address begin, address end) { fix_oop_relocations(begin, end, false); } 378 void fix_oop_relocations() { fix_oop_relocations(NULL, NULL, false); } 379 380 // Scavengable oop support 381 bool on_scavenge_root_list() const { return (_scavenge_root_state & 1) != 0; } 382 protected: 383 enum { sl_on_list = 0x01, sl_marked = 0x10 }; 384 void set_on_scavenge_root_list() { _scavenge_root_state = sl_on_list; } 385 void clear_on_scavenge_root_list() { _scavenge_root_state = 0; } 386 // assertion-checking and pruning logic uses the bits of _scavenge_root_state 387#ifndef PRODUCT 388 void set_scavenge_root_marked() { _scavenge_root_state |= sl_marked; } 389 void clear_scavenge_root_marked() { _scavenge_root_state &= ~sl_marked; } 390 bool scavenge_root_not_marked() { return (_scavenge_root_state &~ sl_on_list) == 0; } 391 // N.B. there is no positive marked query, and we only use the not_marked query for asserts. 392#endif //PRODUCT 393 nmethod* scavenge_root_link() const { return _scavenge_root_link; } 394 void set_scavenge_root_link(nmethod *n) { _scavenge_root_link = n; } 395 396 public: 397 398 // Sweeper support 399 long stack_traversal_mark() { return _stack_traversal_mark; } 400 void set_stack_traversal_mark(long l) { _stack_traversal_mark = l; } 401 402 // implicit exceptions support 403 address continuation_for_implicit_exception(address pc); 404 405 // On-stack replacement support 406 int osr_entry_bci() const { assert(is_osr_method(), "wrong kind of nmethod"); return _entry_bci; } 407 address osr_entry() const { assert(is_osr_method(), "wrong kind of nmethod"); return _osr_entry_point; } 408 void invalidate_osr_method(); 409 nmethod* osr_link() const { return _osr_link; } 410 void set_osr_link(nmethod *n) { _osr_link = n; } 411 412 // Verify calls to dead methods have been cleaned. 413 void verify_clean_inline_caches(); 414 415 // unlink and deallocate this nmethod 416 // Only NMethodSweeper class is expected to use this. NMethodSweeper is not 417 // expected to use any other private methods/data in this class. 418 419 protected: 420 void flush(); 421 422 public: 423 // When true is returned, it is unsafe to remove this nmethod even if 424 // it is a zombie, since the VM or the ServiceThread might still be 425 // using it. 426 bool is_locked_by_vm() const { return _lock_count >0; } 427 428 // See comment at definition of _last_seen_on_stack 429 void mark_as_seen_on_stack(); 430 bool can_convert_to_zombie(); 431 432 // Evolution support. We make old (discarded) compiled methods point to new Method*s. 433 void set_method(Method* method) { _method = method; } 434 435#if INCLUDE_JVMCI 436 oop jvmci_installed_code() { return _jvmci_installed_code ; } 437 char* jvmci_installed_code_name(char* buf, size_t buflen); 438 439 // Update the state of any InstalledCode instance associated with 440 // this nmethod based on the current value of _state. 441 void maybe_invalidate_installed_code(); 442 443 // Helper function to invalidate InstalledCode instances 444 static void invalidate_installed_code(Handle installed_code, TRAPS); 445 446 oop speculation_log() { return _speculation_log ; } 447 448 private: 449 void clear_jvmci_installed_code(); 450 451 public: 452#endif 453 454 protected: 455 virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred); 456#if INCLUDE_JVMCI 457 virtual bool do_unloading_jvmci(BoolObjectClosure* is_alive, bool unloading_occurred); 458#endif 459 460 private: 461 bool do_unloading_scopes(BoolObjectClosure* is_alive, bool unloading_occurred); 462 // Unload a nmethod if the *root object is dead. 463 bool can_unload(BoolObjectClosure* is_alive, oop* root, bool unloading_occurred); 464 bool unload_if_dead_at(RelocIterator *iter_at_oop, BoolObjectClosure* is_alive, bool unloading_occurred); 465 466 public: 467 void oops_do(OopClosure* f) { oops_do(f, false); } 468 void oops_do(OopClosure* f, bool allow_zombie); 469 bool detect_scavenge_root_oops(); 470 void verify_scavenge_root_oops() PRODUCT_RETURN; 471 472 bool test_set_oops_do_mark(); 473 static void oops_do_marking_prologue(); 474 static void oops_do_marking_epilogue(); 475 static bool oops_do_marking_is_active() { return _oops_do_mark_nmethods != NULL; } 476 bool test_oops_do_mark() { return _oops_do_mark_link != NULL; } 477 478 private: 479 ScopeDesc* scope_desc_in(address begin, address end); 480 481 address* orig_pc_addr(const frame* fr) { return (address*) ((address)fr->unextended_sp() + _orig_pc_offset); } 482 483 public: 484 // copying of debugging information 485 void copy_scopes_pcs(PcDesc* pcs, int count); 486 void copy_scopes_data(address buffer, int size); 487 488 // Accessor/mutator for the original pc of a frame before a frame was deopted. 489 address get_original_pc(const frame* fr) { return *orig_pc_addr(fr); } 490 void set_original_pc(const frame* fr, address pc) { *orig_pc_addr(fr) = pc; } 491 492 // jvmti support: 493 void post_compiled_method_load_event(); 494 jmethodID get_and_cache_jmethod_id(); 495 496 // verify operations 497 void verify(); 498 void verify_scopes(); 499 void verify_interrupt_point(address interrupt_point); 500 501 // printing support 502 void print() const; 503 void print_relocations() PRODUCT_RETURN; 504 void print_pcs() PRODUCT_RETURN; 505 void print_scopes() PRODUCT_RETURN; 506 void print_dependencies() PRODUCT_RETURN; 507 void print_value_on(outputStream* st) const PRODUCT_RETURN; 508 void print_calls(outputStream* st) PRODUCT_RETURN; 509 void print_handler_table() PRODUCT_RETURN; 510 void print_nul_chk_table() PRODUCT_RETURN; 511 void print_recorded_oops() PRODUCT_RETURN; 512 void print_recorded_metadata() PRODUCT_RETURN; 513 514 void maybe_print_nmethod(DirectiveSet* directive); 515 void print_nmethod(bool print_code); 516 517 // need to re-define this from CodeBlob else the overload hides it 518 virtual void print_on(outputStream* st) const { CodeBlob::print_on(st); } 519 void print_on(outputStream* st, const char* msg) const; 520 521 // Logging 522 void log_identity(xmlStream* log) const; 523 void log_new_nmethod() const; 524 void log_state_change() const; 525 526 // Prints block-level comments, including nmethod specific block labels: 527 virtual void print_block_comment(outputStream* stream, address block_begin) const { 528 print_nmethod_labels(stream, block_begin); 529 CodeBlob::print_block_comment(stream, block_begin); 530 } 531 void print_nmethod_labels(outputStream* stream, address block_begin) const; 532 533 // Prints a comment for one native instruction (reloc info, pc desc) 534 void print_code_comment_on(outputStream* st, int column, address begin, address end); 535 static void print_statistics() PRODUCT_RETURN; 536 537 // Compiler task identification. Note that all OSR methods 538 // are numbered in an independent sequence if CICountOSR is true, 539 // and native method wrappers are also numbered independently if 540 // CICountNative is true. 541 virtual int compile_id() const { return _compile_id; } 542 const char* compile_kind() const; 543 544 // tells if any of this method's dependencies have been invalidated 545 // (this is expensive!) 546 static void check_all_dependencies(DepChange& changes); 547 548 // tells if this compiled method is dependent on the given changes, 549 // and the changes have invalidated it 550 bool check_dependency_on(DepChange& changes); 551 552 // Evolution support. Tells if this compiled method is dependent on any of 553 // methods m() of class dependee, such that if m() in dependee is replaced, 554 // this compiled method will have to be deoptimized. 555 bool is_evol_dependent_on(Klass* dependee); 556 557 // Fast breakpoint support. Tells if this compiled method is 558 // dependent on the given method. Returns true if this nmethod 559 // corresponds to the given method as well. 560 virtual bool is_dependent_on_method(Method* dependee); 561 562 // is it ok to patch at address? 563 bool is_patchable_at(address instr_address); 564 565 // UseBiasedLocking support 566 ByteSize native_receiver_sp_offset() { 567 return _native_receiver_sp_offset; 568 } 569 ByteSize native_basic_lock_sp_offset() { 570 return _native_basic_lock_sp_offset; 571 } 572 573 // support for code generation 574 static int verified_entry_point_offset() { return offset_of(nmethod, _verified_entry_point); } 575 static int osr_entry_point_offset() { return offset_of(nmethod, _osr_entry_point); } 576 static int state_offset() { return offset_of(nmethod, _state); } 577 578 virtual void metadata_do(void f(Metadata*)); 579 580 NativeCallWrapper* call_wrapper_at(address call) const; 581 NativeCallWrapper* call_wrapper_before(address return_pc) const; 582 address call_instruction_address(address pc) const; 583 584 virtual CompiledStaticCall* compiledStaticCall_at(Relocation* call_site) const; 585 virtual CompiledStaticCall* compiledStaticCall_at(address addr) const; 586 virtual CompiledStaticCall* compiledStaticCall_before(address addr) const; 587}; 588 589// Locks an nmethod so its code will not get removed and it will not 590// be made into a zombie, even if it is a not_entrant method. After the 591// nmethod becomes a zombie, if CompiledMethodUnload event processing 592// needs to be done, then lock_nmethod() is used directly to keep the 593// generated code from being reused too early. 594class nmethodLocker : public StackObj { 595 CompiledMethod* _nm; 596 597 public: 598 599 // note: nm can be NULL 600 // Only JvmtiDeferredEvent::compiled_method_unload_event() 601 // should pass zombie_ok == true. 602 static void lock_nmethod(CompiledMethod* nm, bool zombie_ok = false); 603 static void unlock_nmethod(CompiledMethod* nm); // (ditto) 604 605 nmethodLocker(address pc); // derive nm from pc 606 nmethodLocker(nmethod *nm) { _nm = nm; lock_nmethod(_nm); } 607 nmethodLocker(CompiledMethod *nm) { 608 _nm = nm; 609 lock(_nm); 610 } 611 612 static void lock(CompiledMethod* method) { 613 if (method == NULL) return; 614 lock_nmethod(method); 615 } 616 617 static void unlock(CompiledMethod* method) { 618 if (method == NULL) return; 619 unlock_nmethod(method); 620 } 621 622 nmethodLocker() { _nm = NULL; } 623 ~nmethodLocker() { 624 unlock(_nm); 625 } 626 627 CompiledMethod* code() { return _nm; } 628 void set_code(CompiledMethod* new_nm) { 629 unlock(_nm); // note: This works even if _nm==new_nm. 630 _nm = new_nm; 631 lock(_nm); 632 } 633}; 634 635#endif // SHARE_VM_CODE_NMETHOD_HPP 636