JDK14/Java14源码在线阅读
/*
* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "code/compiledIC.hpp"
#include "code/compiledMethod.inline.hpp"
#include "code/exceptionHandlerTable.hpp"
#include "code/scopeDesc.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/barrierSetNMethod.hpp"
#include "gc/shared/gcBehaviours.hpp"
#include "interpreter/bytecode.inline.hpp"
#include "logging/log.hpp"
#include "logging/logTag.hpp"
#include "memory/resourceArea.hpp"
#include "oops/methodData.hpp"
#include "oops/method.inline.hpp"
#include "prims/methodHandles.hpp"
#include "runtime/atomic.hpp"
#include "runtime/deoptimization.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/sharedRuntime.hpp"
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)
: CodeBlob(name, type, layout, frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
_mark_for_deoptimization_status(not_marked),
_method(method),
_gc_data(NULL)
{
init_defaults();
}
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)
: CodeBlob(name, type, CodeBlobLayout((address) this, size, header_size, cb), cb,
frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments),
_mark_for_deoptimization_status(not_marked),
_method(method),
_gc_data(NULL)
{
init_defaults();
}
void CompiledMethod::init_defaults() {
_has_unsafe_access = 0;
_has_method_handle_invokes = 0;
_lazy_critical_native = 0;
_has_wide_vectors = 0;
}
bool CompiledMethod::is_method_handle_return(address return_pc) {
if (!has_method_handle_invokes()) return false;
PcDesc* pd = pc_desc_at(return_pc);
if (pd == NULL)
return false;
return pd->is_method_handle_invoke();
}
// Returns a string version of the method state.
const char* CompiledMethod::state() const {
int state = get_state();
switch (state) {
case not_installed:
return "not installed";
case in_use:
return "in use";
case not_used:
return "not_used";
case not_entrant:
return "not_entrant";
case zombie:
return "zombie";
case unloaded:
return "unloaded";
default:
fatal("unexpected method state: %d", state);
return NULL;
}
}
//-----------------------------------------------------------------------------
void CompiledMethod::mark_for_deoptimization(bool inc_recompile_counts) {
MutexLocker ml(CompiledMethod_lock->owned_by_self() ? NULL : CompiledMethod_lock,
Mutex::_no_safepoint_check_flag);
_mark_for_deoptimization_status = (inc_recompile_counts ? deoptimize : deoptimize_noupdate);
}
//-----------------------------------------------------------------------------
ExceptionCache* CompiledMethod::exception_cache_acquire() const {
return Atomic::load_acquire(&_exception_cache);
}
void CompiledMethod::add_exception_cache_entry(ExceptionCache* new_entry) {
assert(ExceptionCache_lock->owned_by_self(),"Must hold the ExceptionCache_lock");
assert(new_entry != NULL,"Must be non null");
assert(new_entry->next() == NULL, "Must be null");
for (;;) {
ExceptionCache *ec = exception_cache();
if (ec != NULL) {
Klass* ex_klass = ec->exception_type();
if (!ex_klass->is_loader_alive()) {
// We must guarantee that entries are not inserted with new next pointer
// edges to ExceptionCache entries with dead klasses, due to bad interactions
// with concurrent ExceptionCache cleanup. Therefore, the inserts roll
// the head pointer forward to the first live ExceptionCache, so that the new
// next pointers always point at live ExceptionCaches, that are not removed due
// to concurrent ExceptionCache cleanup.
ExceptionCache* next = ec->next();
if (Atomic::cmpxchg(&_exception_cache, ec, next) == ec) {
CodeCache::release_exception_cache(ec);
}
continue;
}
ec = exception_cache();
if (ec != NULL) {
new_entry->set_next(ec);
}
}
if (Atomic::cmpxchg(&_exception_cache, ec, new_entry) == ec) {
return;
}
}
}
void CompiledMethod::clean_exception_cache() {
// For each nmethod, only a single thread may call this cleanup function
// at the same time, whether called in STW cleanup or concurrent cleanup.
// Note that if the GC is processing exception cache cleaning in a concurrent phase,
// then a single writer may contend with cleaning up the head pointer to the
// first ExceptionCache node that has a Klass* that is alive. That is fine,
// as long as there is no concurrent cleanup of next pointers from concurrent writers.
// And the concurrent writers do not clean up next pointers, only the head.
// Also note that concurent readers will walk through Klass* pointers that are not
// alive. That does not cause ABA problems, because Klass* is deleted after
// a handshake with all threads, after all stale ExceptionCaches have been
// unlinked. That is also when the CodeCache::exception_cache_purge_list()
// is deleted, with all ExceptionCache entries that were cleaned concurrently.
// That similarly implies that CAS operations on ExceptionCache entries do not
// suffer from ABA problems as unlinking and deletion is separated by a global
// handshake operation.
ExceptionCache* prev = NULL;
ExceptionCache* curr = exception_cache_acquire();
while (curr != NULL) {
ExceptionCache* next = curr->next();
if (!curr->exception_type()->is_loader_alive()) {
if (prev == NULL) {
// Try to clean head; this is contended by concurrent inserts, that
// both lazily clean the head, and insert entries at the head. If
// the CAS fails, the operation is restarted.
if (Atomic::cmpxchg(&_exception_cache, curr, next) != curr) {
prev = NULL;
curr = exception_cache_acquire();
continue;
}
} else {
// It is impossible to during cleanup connect the next pointer to
// an ExceptionCache that has not been published before a safepoint
// prior to the cleanup. Therefore, release is not required.
prev->set_next(next);
}
// prev stays the same.
CodeCache::release_exception_cache(curr);
} else {
prev = curr;
}
curr = next;
}
}
// public method for accessing the exception cache
// These are the public access methods.
address CompiledMethod::handler_for_exception_and_pc(Handle exception, address pc) {
// We never grab a lock to read the exception cache, so we may
// have false negatives. This is okay, as it can only happen during
// the first few exception lookups for a given nmethod.
ExceptionCache* ec = exception_cache_acquire();
while (ec != NULL) {
address ret_val;
if ((ret_val = ec->match(exception,pc)) != NULL) {
return ret_val;
}
ec = ec->next();
}
return NULL;
}
void CompiledMethod::add_handler_for_exception_and_pc(Handle exception, address pc, address handler) {
// There are potential race conditions during exception cache updates, so we
// must own the ExceptionCache_lock before doing ANY modifications. Because
// we don't lock during reads, it is possible to have several threads attempt
// to update the cache with the same data. We need to check for already inserted
// copies of the current data before adding it.
MutexLocker ml(ExceptionCache_lock);
ExceptionCache* target_entry = exception_cache_entry_for_exception(exception);
if (target_entry == NULL || !target_entry->add_address_and_handler(pc,handler)) {
target_entry = new ExceptionCache(exception,pc,handler);
add_exception_cache_entry(target_entry);
}
}
// private method for handling exception cache
// These methods are private, and used to manipulate the exception cache
// directly.
ExceptionCache* CompiledMethod::exception_cache_entry_for_exception(Handle exception) {
ExceptionCache* ec = exception_cache_acquire();
while (ec != NULL) {
if (ec->match_exception_with_space(exception)) {
return ec;
}
ec = ec->next();
}
return NULL;
}
//-------------end of code for ExceptionCache--------------
bool CompiledMethod::is_at_poll_return(address pc) {
RelocIterator iter(this, pc, pc+1);
while (iter.next()) {
if (iter.type() == relocInfo::poll_return_type)
return true;
}
return false;
}
bool CompiledMethod::is_at_poll_or_poll_return(address pc) {
RelocIterator iter(this, pc, pc+1);
while (iter.next()) {
relocInfo::relocType t = iter.type();
if (t == relocInfo::poll_return_type || t == relocInfo::poll_type)
return true;
}
return false;
}
void CompiledMethod::verify_oop_relocations() {
// Ensure sure that the code matches the current oop values
RelocIterator iter(this, NULL, NULL);
while (iter.next()) {
if (iter.type() == relocInfo::oop_type) {
oop_Relocation* reloc = iter.oop_reloc();
if (!reloc->oop_is_immediate()) {
reloc->verify_oop_relocation();
}
}
}
}
ScopeDesc* CompiledMethod::scope_desc_at(address pc) {
PcDesc* pd = pc_desc_at(pc);
guarantee(pd != NULL, "scope must be present");
return new ScopeDesc(this, pd->scope_decode_offset(),
pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
pd->return_oop());
}
ScopeDesc* CompiledMethod::scope_desc_near(address pc) {
PcDesc* pd = pc_desc_near(pc);
guarantee(pd != NULL, "scope must be present");
return new ScopeDesc(this, pd->scope_decode_offset(),
pd->obj_decode_offset(), pd->should_reexecute(), pd->rethrow_exception(),
pd->return_oop());
}
address CompiledMethod::oops_reloc_begin() const {
// If the method is not entrant or zombie then a JMP is plastered over the
// first few bytes. If an oop in the old code was there, that oop
// should not get GC'd. Skip the first few bytes of oops on
// not-entrant methods.
if (frame_complete_offset() != CodeOffsets::frame_never_safe &&
code_begin() + frame_complete_offset() >
verified_entry_point() + NativeJump::instruction_size)
{
// If we have a frame_complete_offset after the native jump, then there
// is no point trying to look for oops before that. This is a requirement
// for being allowed to scan oops concurrently.
return code_begin() + frame_complete_offset();
}
// It is not safe to read oops concurrently using entry barriers, if their
// location depend on whether the nmethod is entrant or not.
assert(BarrierSet::barrier_set()->barrier_set_nmethod() == NULL, "Not safe oop scan");
address low_boundary = verified_entry_point();
if (!is_in_use() && is_nmethod()) {
low_boundary += NativeJump::instruction_size;
// %%% Note: On SPARC we patch only a 4-byte trap, not a full NativeJump.
// This means that the low_boundary is going to be a little too high.
// This shouldn't matter, since oops of non-entrant methods are never used.
// In fact, why are we bothering to look at oops in a non-entrant method??
}
return low_boundary;
}
int CompiledMethod::verify_icholder_relocations() {
ResourceMark rm;
int count = 0;
RelocIterator iter(this);
while(iter.next()) {
if (iter.type() == relocInfo::virtual_call_type) {
if (CompiledIC::is_icholder_call_site(iter.virtual_call_reloc(), this)) {
CompiledIC *ic = CompiledIC_at(&iter);
if (TraceCompiledIC) {
tty->print("noticed icholder " INTPTR_FORMAT " ", p2i(ic->cached_icholder()));
ic->print();
}
assert(ic->cached_icholder() != NULL, "must be non-NULL");
count++;
}
}
}
return count;
}
// Method that knows how to preserve outgoing arguments at call. This method must be
// called with a frame corresponding to a Java invoke
void CompiledMethod::preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) {
if (method() != NULL && !method()->is_native()) {
address pc = fr.pc();
SimpleScopeDesc ssd(this, pc);
Bytecode_invoke call(methodHandle(Thread::current(), ssd.method()), ssd.bci());
bool has_receiver = call.has_receiver();
bool has_appendix = call.has_appendix();
Symbol* signature = call.signature();
// The method attached by JIT-compilers should be used, if present.
// Bytecode can be inaccurate in such case.
Method* callee = attached_method_before_pc(pc);
if (callee != NULL) {
has_receiver = !(callee->access_flags().is_static());
has_appendix = false;
signature = callee->signature();
}
fr.oops_compiled_arguments_do(signature, has_receiver, has_appendix, reg_map, f);
}
}
Method* CompiledMethod::attached_method(address call_instr) {
assert(code_contains(call_instr), "not part of the nmethod");
RelocIterator iter(this, call_instr, call_instr + 1);
while (iter.next()) {
if (iter.addr() == call_instr) {
switch(iter.type()) {
case relocInfo::static_call_type: return iter.static_call_reloc()->method_value();
case relocInfo::opt_virtual_call_type: return iter.opt_virtual_call_reloc()->method_value();
case relocInfo::virtual_call_type: return iter.virtual_call_reloc()->method_value();
default: break;
}
}
}
return NULL; // not found
}
Method* CompiledMethod::attached_method_before_pc(address pc) {
if (NativeCall::is_call_before(pc)) {
NativeCall* ncall = nativeCall_before(pc);
return attached_method(ncall->instruction_address());
}
return NULL; // not a call
}
void CompiledMethod::clear_inline_caches() {
assert(SafepointSynchronize::is_at_safepoint(), "cleaning of IC's only allowed at safepoint");
if (is_zombie()) {
return;
}
RelocIterator iter(this);
while (iter.next()) {
iter.reloc()->clear_inline_cache();
}
}
// Clear IC callsites, releasing ICStubs of all compiled ICs
// as well as any associated CompiledICHolders.
void CompiledMethod::clear_ic_callsites() {
assert(CompiledICLocker::is_safe(this), "mt unsafe call");
ResourceMark rm;
RelocIterator iter(this);
while(iter.next()) {
if (iter.type() == relocInfo::virtual_call_type) {
CompiledIC* ic = CompiledIC_at(&iter);
ic->set_to_clean(false);
}
}
}
#ifdef ASSERT
// Check class_loader is alive for this bit of metadata.
class CheckClass : public MetadataClosure {
void do_metadata(Metadata* md) {
Klass* klass = NULL;
if (md->is_klass()) {
klass = ((Klass*)md);
} else if (md->is_method()) {
klass = ((Method*)md)->method_holder();
} else if (md->is_methodData()) {
klass = ((MethodData*)md)->method()->method_holder();
} else {
md->print();
ShouldNotReachHere();
}
assert(klass->is_loader_alive(), "must be alive");
}
};
#endif // ASSERT
bool CompiledMethod::clean_ic_if_metadata_is_dead(CompiledIC *ic) {
if (ic->is_clean()) {
return true;
}
if (ic->is_icholder_call()) {
// The only exception is compiledICHolder metdata which may
// yet be marked below. (We check this further below).
CompiledICHolder* cichk_metdata = ic->cached_icholder();
if (cichk_metdata->is_loader_alive()) {
return true;
}
} else {
Metadata* ic_metdata = ic->cached_metadata();
if (ic_metdata != NULL) {
if (ic_metdata->is_klass()) {
if (((Klass*)ic_metdata)->is_loader_alive()) {
return true;
}
} else if (ic_metdata->is_method()) {
Method* method = (Method*)ic_metdata;
assert(!method->is_old(), "old method should have been cleaned");
if (method->method_holder()->is_loader_alive()) {
return true;
}
} else {
ShouldNotReachHere();
}
}
}
return ic->set_to_clean();
}
// Clean references to unloaded nmethods at addr from this one, which is not unloaded.
template <class CompiledICorStaticCall>
static bool clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from,
bool clean_all) {
// Ok, to lookup references to zombies here
CodeBlob *cb = CodeCache::find_blob_unsafe(addr);
CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
if (nm != NULL) {
// Clean inline caches pointing to both zombie and not_entrant methods
if (clean_all || !nm->is_in_use() || nm->is_unloading() || (nm->method()->code() != nm)) {
// Inline cache cleaning should only be initiated on CompiledMethods that have been
// observed to be is_alive(). However, with concurrent code cache unloading, it is
// possible that by now, the state has been racingly flipped to unloaded if the nmethod
// being cleaned is_unloading(). This is fine, because if that happens, then the inline
// caches have already been cleaned under the same CompiledICLocker that we now hold during
// inline cache cleaning, and we will simply walk the inline caches again, and likely not
// find much of interest to clean. However, this race prevents us from asserting that the
// nmethod is_alive(). The is_unloading() function is completely monotonic; once set due
// to an oop dying, it remains set forever until freed. Because of that, all unloaded
// nmethods are is_unloading(), but notably, an unloaded nmethod may also subsequently
// become zombie (when the sweeper converts it to zombie). Therefore, the most precise
// sanity check we can check for in this context is to not allow zombies.
assert(!from->is_zombie(), "should not clean inline caches on zombies");
if (!ic->set_to_clean(!from->is_unloading())) {
return false;
}
assert(ic->is_clean(), "nmethod " PTR_FORMAT "not clean %s", p2i(from), from->method()->name_and_sig_as_C_string());
}
}
return true;
}
static bool clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from,
bool clean_all) {
return clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from, clean_all);
}
static bool clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from,
bool clean_all) {
return clean_if_nmethod_is_unloaded(csc, csc->destination(), from, clean_all);
}
// Cleans caches in nmethods that point to either classes that are unloaded
// or nmethods that are unloaded.
//
// Can be called either in parallel by G1 currently or after all
// nmethods are unloaded. Return postponed=true in the parallel case for
// inline caches found that point to nmethods that are not yet visited during
// the do_unloading walk.
bool CompiledMethod::unload_nmethod_caches(bool unloading_occurred) {
ResourceMark rm;
// Exception cache only needs to be called if unloading occurred
if (unloading_occurred) {
clean_exception_cache();
}
if (!cleanup_inline_caches_impl(unloading_occurred, false)) {
return false;
}
#ifdef ASSERT
// Check that the metadata embedded in the nmethod is alive
CheckClass check_class;
metadata_do(&check_class);
#endif
return true;
}
void CompiledMethod::run_nmethod_entry_barrier() {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != NULL) {
// We want to keep an invariant that nmethods found through iterations of a Thread's
// nmethods found in safepoints have gone through an entry barrier and are not armed.
// By calling this nmethod entry barrier, it plays along and acts
// like any other nmethod found on the stack of a thread (fewer surprises).
nmethod* nm = as_nmethod_or_null();
if (nm != NULL) {
bool alive = bs_nm->nmethod_entry_barrier(nm);
assert(alive, "should be alive");
}
}
}
void CompiledMethod::cleanup_inline_caches(bool clean_all) {
for (;;) {
ICRefillVerifier ic_refill_verifier;
{ CompiledICLocker ic_locker(this);
if (cleanup_inline_caches_impl(false, clean_all)) {
return;
}
}
// Call this nmethod entry barrier from the sweeper.
run_nmethod_entry_barrier();
InlineCacheBuffer::refill_ic_stubs();
}
}
// Called to clean up after class unloading for live nmethods and from the sweeper
// for all methods.
bool CompiledMethod::cleanup_inline_caches_impl(bool unloading_occurred, bool clean_all) {
assert(CompiledICLocker::is_safe(this), "mt unsafe call");
ResourceMark rm;
// Find all calls in an nmethod and clear the ones that point to non-entrant,
// zombie and unloaded nmethods.
RelocIterator iter(this, oops_reloc_begin());
bool is_in_static_stub = false;
while(iter.next()) {
switch (iter.type()) {
case relocInfo::virtual_call_type:
if (unloading_occurred) {
// If class unloading occurred we first clear ICs where the cached metadata
// is referring to an unloaded klass or method.
if (!clean_ic_if_metadata_is_dead(CompiledIC_at(&iter))) {
return false;
}
}
if (!clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all)) {
return false;
}
break;
case relocInfo::opt_virtual_call_type:
if (!clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all)) {
return false;
}
break;
case relocInfo::static_call_type:
if (!clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, clean_all)) {
return false;
}
break;
case relocInfo::static_stub_type: {
is_in_static_stub = true;
break;
}
case relocInfo::metadata_type: {
// Only the metadata relocations contained in static/opt virtual call stubs
// contains the Method* passed to c2i adapters. It is the only metadata
// relocation that needs to be walked, as it is the one metadata relocation
// that violates the invariant that all metadata relocations have an oop
// in the compiled method (due to deferred resolution and code patching).
// This causes dead metadata to remain in compiled methods that are not
// unloading. Unless these slippery metadata relocations of the static
// stubs are at least cleared, subsequent class redefinition operations
// will access potentially free memory, and JavaThread execution
// concurrent to class unloading may call c2i adapters with dead methods.
if (!is_in_static_stub) {
// The first metadata relocation after a static stub relocation is the
// metadata relocation of the static stub used to pass the Method* to
// c2i adapters.
continue;
}
is_in_static_stub = false;
metadata_Relocation* r = iter.metadata_reloc();
Metadata* md = r->metadata_value();
if (md != NULL && md->is_method()) {
Method* method = static_cast<Method*>(md);
if (!method->method_holder()->is_loader_alive()) {
Atomic::store(r->metadata_addr(), (Method*)NULL);
if (!r->metadata_is_immediate()) {
r->fix_metadata_relocation();
}
}
}
break;
}
default:
break;
}
}
return true;
}
// Iterating over all nmethods, e.g. with the help of CodeCache::nmethods_do(fun) was found
// to not be inherently safe. There is a chance that fields are seen which are not properly
// initialized. This happens despite the fact that nmethods_do() asserts the CodeCache_lock
// to be held.
// To bundle knowledge about necessary checks in one place, this function was introduced.
// It is not claimed that these checks are sufficient, but they were found to be necessary.
bool CompiledMethod::nmethod_access_is_safe(nmethod* nm) {
Method* method = (nm == NULL) ? NULL : nm->method(); // nm->method() may be uninitialized, i.e. != NULL, but invalid
return (nm != NULL) && (method != NULL) && (method->signature() != NULL) &&
!nm->is_zombie() && !nm->is_not_installed() &&
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