/*
* Copyright (c) 1998, 2022, 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 "gc/shared/collectedHeap.hpp"
#include "gc/shared/oopStorage.inline.hpp"
#include "gc/shared/oopStorageSet.hpp"
#include "logging/log.hpp"
#include "memory/iterator.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/javaThread.inline.hpp"
#include "runtime/jniHandles.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
OopStorage* JNIHandles::global_handles() {
return _global_handles;
}
OopStorage* JNIHandles::weak_global_handles() {
return _weak_global_handles;
}
// Serviceability agent support.
OopStorage* JNIHandles::_global_handles = NULL;
OopStorage* JNIHandles::_weak_global_handles = NULL;
void jni_handles_init() {
JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global", mtInternal);
JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak", mtInternal);
}
jobject JNIHandles::make_local(oop obj) {
return make_local(JavaThread::current(), obj);
}
// Used by NewLocalRef which requires NULL on out-of-memory
jobject JNIHandles::make_local(JavaThread* thread, oop obj, AllocFailType alloc_failmode) {
if (obj == NULL) {
return NULL; // ignore null handles
} else {
assert(oopDesc::is_oop(obj), "not an oop");
assert(!current_thread_in_native(), "must not be in native");
return thread->active_handles()->allocate_handle(thread, obj, alloc_failmode);
}
}
static void report_handle_allocation_failure(AllocFailType alloc_failmode,
const char* handle_kind) {
if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
// Fake size value, since we don't know the min allocation size here.
vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
"Cannot create %s JNI handle", handle_kind);
} else {
assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
}
}
jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
assert(!current_thread_in_native(), "must not be in native");
jobject res = NULL;
if (!obj.is_null()) {
// ignore null handles
assert(oopDesc::is_oop(obj()), "not an oop");
oop* ptr = global_handles()->allocate();
// Return NULL on allocation failure.
if (ptr != NULL) {
assert(*ptr == NULL, "invariant");
NativeAccess<>::oop_store(ptr, obj());
res = reinterpret_cast<jobject>(ptr);
} else {
report_handle_allocation_failure(alloc_failmode, "global");
}
}
return res;
}
jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
assert(!current_thread_in_native(), "must not be in native");
jobject res = NULL;
if (!obj.is_null()) {
// ignore null handles
assert(oopDesc::is_oop(obj()), "not an oop");
oop* ptr = weak_global_handles()->allocate();
// Return NULL on allocation failure.
if (ptr != NULL) {
assert(*ptr == NULL, "invariant");
NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
res = reinterpret_cast<jobject>(tptr);
} else {
report_handle_allocation_failure(alloc_failmode, "weak global");
}
}
return res;
}
// Resolve some erroneous cases to NULL, rather than treating them as
// possibly unchecked errors. In particular, deleted handles are
// treated as NULL (though a deleted and later reallocated handle
// isn't detected).
oop JNIHandles::resolve_external_guard(jobject handle) {
oop result = NULL;
if (handle != NULL) {
result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
}
return result;
}
bool JNIHandles::is_global_weak_cleared(jweak handle) {
assert(handle != NULL, "precondition");
assert(is_jweak(handle), "not a weak handle");
oop* oop_ptr = jweak_ptr(handle);
oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
return value == NULL;
}
void JNIHandles::destroy_global(jobject handle) {
if (handle != NULL) {
assert(!is_jweak(handle), "wrong method for destroying jweak");
oop* oop_ptr = jobject_ptr(handle);
NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
global_handles()->release(oop_ptr);
}
}
void JNIHandles::destroy_weak_global(jobject handle) {
if (handle != NULL) {
assert(is_jweak(handle), "JNI handle not jweak");
oop* oop_ptr = jweak_ptr(handle);
NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
weak_global_handles()->release(oop_ptr);
}
}
void JNIHandles::oops_do(OopClosure* f) {
global_handles()->oops_do(f);
}
void JNIHandles::weak_oops_do(OopClosure* f) {
weak_global_handles()->weak_oops_do(f);
}
bool JNIHandles::is_global_storage(const OopStorage* storage) {
return _global_handles == storage;
}
inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
}
jobjectRefType JNIHandles::handle_type(JavaThread* thread, jobject handle) {
assert(handle != NULL, "precondition");
jobjectRefType result = JNIInvalidRefType;
if (is_jweak(handle)) {
if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
result = JNIWeakGlobalRefType;
}
} else {
switch (global_handles()->allocation_status(jobject_ptr(handle))) {
case OopStorage::ALLOCATED_ENTRY:
result = JNIGlobalRefType;
break;
case OopStorage::UNALLOCATED_ENTRY:
break; // Invalid global handle
case OopStorage::INVALID_ENTRY:
// Not in global storage. Might be a local handle.
if (is_local_handle(thread, handle) || is_frame_handle(thread, handle)) {
result = JNILocalRefType;
}
break;
default:
ShouldNotReachHere();
}
}
return result;
}
bool JNIHandles::is_local_handle(JavaThread* thread, jobject handle) {
assert(handle != NULL, "precondition");
JNIHandleBlock* block = thread->active_handles();
// Look back past possible native calls to jni_PushLocalFrame.
while (block != NULL) {
if (block->chain_contains(handle)) {
return true;
}
block = block->pop_frame_link();
}
return false;
}
// Determine if the handle is somewhere in the current thread's stack.
// We easily can't isolate any particular stack frame the handle might
// come from, so we'll check the whole stack.
bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
assert(handle != NULL, "precondition");
// If there is no java frame, then this must be top level code, such
// as the java command executable, in which case, this type of handle
// is not permitted.
return (thr->has_last_Java_frame() &&
thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
}
bool JNIHandles::is_global_handle(jobject handle) {
assert(handle != NULL, "precondition");
return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
}
bool JNIHandles::is_weak_global_handle(jobject handle) {
assert(handle != NULL, "precondition");
return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
}
// We assume this is called at a safepoint: no lock is needed.
void JNIHandles::print_on(outputStream* st) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
global_handles()->allocation_count(),
weak_global_handles()->allocation_count());
st->cr();
st->flush();
}
void JNIHandles::print() { print_on(tty); }
class VerifyJNIHandles: public OopClosure {
public:
virtual void do_oop(oop* root) {
guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
}
virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
};
void JNIHandles::verify() {
VerifyJNIHandles verify_handle;
oops_do(&verify_handle);
weak_oops_do(&verify_handle);
}
// This method is implemented here to avoid circular includes between
// jniHandles.hpp and thread.hpp.
bool JNIHandles::current_thread_in_native() {
Thread* thread = Thread::current();
return (thread->is_Java_thread() &&
JavaThread::cast(thread)->thread_state() == _thread_in_native);
}
int JNIHandleBlock::_blocks_allocated = 0;
static inline bool is_tagged_free_list(uintptr_t value) {
return (value & 1u) != 0;
}
static inline uintptr_t tag_free_list(uintptr_t value) {
return value | 1u;
}
static inline uintptr_t untag_free_list(uintptr_t value) {
return value & ~(uintptr_t)1u;
}
// There is a freelist of handles running through the JNIHandleBlock
// with a tagged next pointer, distinguishing these next pointers from
// oops. The freelist handling currently relies on the size of oops
// being the same as a native pointer. If this ever changes, then
// this freelist handling must change too.
STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
#ifdef ASSERT
void JNIHandleBlock::zap() {
// Zap block values
_top = 0;
for (int index = 0; index < block_size_in_oops; index++) {
// NOT using Access here; just bare clobbering to NULL, since the
// block no longer contains valid oops.
_handles[index] = 0;
}
}
#endif // ASSERT
JNIHandleBlock* JNIHandleBlock::allocate_block(JavaThread* thread, AllocFailType alloc_failmode) {
// The VM thread can allocate a handle block in behalf of another thread during a safepoint.
assert(thread == NULL || thread == Thread::current() || SafepointSynchronize::is_at_safepoint(),
"sanity check");
JNIHandleBlock* block;
// Check the thread-local free list for a block so we don't
// have to acquire a mutex.
if (thread != NULL && thread->free_handle_block() != NULL) {
block = thread->free_handle_block();
thread->set_free_handle_block(block->_next);
} else {
// Allocate new block
if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
block = new (std::nothrow) JNIHandleBlock();
if (block == NULL) {
return NULL;
}
} else {
block = new JNIHandleBlock();
}
Atomic::inc(&_blocks_allocated);
block->zap();
}
block->_top = 0;
block->_next = NULL;
block->_pop_frame_link = NULL;
// _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
debug_only(block->_last = NULL);
debug_only(block->_free_list = NULL);
debug_only(block->_allocate_before_rebuild = -1);
return block;
}
void JNIHandleBlock::release_block(JNIHandleBlock* block, JavaThread* thread) {
assert(thread == NULL || thread == Thread::current(), "sanity check");
JNIHandleBlock* pop_frame_link = block->pop_frame_link();
// Put returned block at the beginning of the thread-local free list.
// Note that if thread == NULL, we use it as an implicit argument that
// we _don't_ want the block to be kept on the free_handle_block.
// See for instance JavaThread::exit().
if (thread != NULL ) {
block->zap();
JNIHandleBlock* freelist = thread->free_handle_block();
block->_pop_frame_link = NULL;
thread->set_free_handle_block(block);
// Add original freelist to end of chain
if ( freelist != NULL ) {
while ( block->_next != NULL ) block = block->_next;
block->_next = freelist;
}
block = NULL;
} else {
DEBUG_ONLY(block->set_pop_frame_link(NULL));
while (block != NULL) {
JNIHandleBlock* next = block->_next;
Atomic::dec(&_blocks_allocated);
assert(block->pop_frame_link() == NULL, "pop_frame_link should be NULL");
delete block;
block = next;
}
}
if (pop_frame_link != NULL) {
// As a sanity check we release blocks pointed to by the pop_frame_link.
// This should never happen (only if PopLocalFrame is not called the
// correct number of times).
release_block(pop_frame_link, thread);
}
}
void JNIHandleBlock::oops_do(OopClosure* f) {
JNIHandleBlock* current_chain = this;
// Iterate over chain of blocks, followed by chains linked through the
// pop frame links.
while (current_chain != NULL) {
for (JNIHandleBlock* current = current_chain; current != NULL;
current = current->_next) {
assert(current == current_chain || current->pop_frame_link() == NULL,
"only blocks first in chain should have pop frame link set");
for (int index = 0; index < current->_top; index++) {
uintptr_t* addr = &(current->_handles)[index];
uintptr_t value = *addr;
// traverse heap pointers only, not deleted handles or free list
// pointers
if (value != 0 && !is_tagged_free_list(value)) {
oop* root = (oop*)addr;
f->do_oop(root);
}
}
// the next handle block is valid only if current block is full
if (current->_top < block_size_in_oops) {
break;
}
}
current_chain = current_chain->pop_frame_link();
}
}
jobject JNIHandleBlock::allocate_handle(JavaThread* caller, oop obj, AllocFailType alloc_failmode) {
assert(Universe::heap()->is_in(obj), "sanity check");
if (_top == 0) {
// This is the first allocation or the initial block got zapped when
// entering a native function. If we have any following blocks they are
// not valid anymore.
for (JNIHandleBlock* current = _next; current != NULL;
current = current->_next) {
assert(current->_last == NULL, "only first block should have _last set");
assert(current->_free_list == NULL,
"only first block should have _free_list set");
if (current->_top == 0) {
// All blocks after the first clear trailing block are already cleared.
#ifdef ASSERT
for (current = current->_next; current != NULL; current = current->_next) {
assert(current->_top == 0, "trailing blocks must already be cleared");
}
#endif
break;
}
current->_top = 0;
current->zap();
}
// Clear initial block
_free_list = NULL;
_allocate_before_rebuild = 0;
_last = this;
zap();
}
// Try last block
if (_last->_top < block_size_in_oops) {
oop* handle = (oop*)&(_last->_handles)[_last->_top++];
NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
return (jobject) handle;
}
// Try free list
if (_free_list != NULL) {
oop* handle = (oop*)_free_list;
_free_list = (uintptr_t*) untag_free_list(*_free_list);
NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
return (jobject) handle;
}
// Check if unused block follow last
if (_last->_next != NULL) {
// update last and retry
_last = _last->_next;
return allocate_handle(caller, obj, alloc_failmode);
}
// No space available, we have to rebuild free list or expand
if (_allocate_before_rebuild == 0) {
rebuild_free_list(); // updates _allocate_before_rebuild counter
} else {
_last->_next = JNIHandleBlock::allocate_block(caller, alloc_failmode);
if (_last->_next == NULL) {
return NULL;
}
_last = _last->_next;
_allocate_before_rebuild--;
}
return allocate_handle(caller, obj, alloc_failmode); // retry
}
void JNIHandleBlock::rebuild_free_list() {
assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
int free = 0;
int blocks = 0;
for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
for (int index = 0; index < current->_top; index++) {
uintptr_t* handle = &(current->_handles)[index];
if (*handle == 0) {
// this handle was cleared out by a delete call, reuse it
*handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
_free_list = handle;
free++;
}
}
// we should not rebuild free list if there are unused handles at the end
assert(current->_top == block_size_in_oops, "just checking");
blocks++;
}
// Heuristic: if more than half of the handles are free we rebuild next time
// as well, otherwise we append a corresponding number of new blocks before
// attempting a free list rebuild again.
int total = blocks * block_size_in_oops;
int extra = total - 2*free;
if (extra > 0) {
// Not as many free handles as we would like - compute number of new blocks to append
_allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
}
}
bool JNIHandleBlock::contains(jobject handle) const {
return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
}
bool JNIHandleBlock::chain_contains(jobject handle) const {
for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
if (current->contains(handle)) {
return true;
}
}
return false;
}
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