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/*
* Copyright (c) 1997, 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/codeBlob.hpp"
#include "code/codeCache.hpp"
#include "code/stubs.hpp"
#include "memory/allocation.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/align.hpp"
// Implementation of StubQueue
//
// Standard wrap-around queue implementation; the queue dimensions
// are specified by the _queue_begin & _queue_end indices. The queue
// can be in two states (transparent to the outside):
//
// a) contiguous state: all queue entries in one block (or empty)
//
// Queue: |...|XXXXXXX|...............|
// ^0 ^begin ^end ^size = limit
// |_______|
// one block
//
// b) non-contiguous state: queue entries in two blocks
//
// Queue: |XXX|.......|XXXXXXX|.......|
// ^0 ^end ^begin ^limit ^size
// |___| |_______|
// 1st block 2nd block
//
// In the non-contiguous state, the wrap-around point is
// indicated via the _buffer_limit index since the last
// queue entry may not fill up the queue completely in
// which case we need to know where the 2nd block's end
// is to do the proper wrap-around. When removing the
// last entry of the 2nd block, _buffer_limit is reset
// to _buffer_size.
//
// CAUTION: DO NOT MESS WITH THIS CODE IF YOU CANNOT PROVE
// ITS CORRECTNESS! THIS CODE IS MORE SUBTLE THAN IT LOOKS!
StubQueue::StubQueue(StubInterface* stub_interface, int buffer_size,
Mutex* lock, const char* name) : _mutex(lock) {
intptr_t size = align_up(buffer_size, 2*BytesPerWord);
BufferBlob* blob = BufferBlob::create(name, size);
if( blob == NULL) {
vm_exit_out_of_memory(size, OOM_MALLOC_ERROR, "CodeCache: no room for %s", name);
}
_stub_interface = stub_interface;
_buffer_size = blob->content_size();
_buffer_limit = blob->content_size();
_stub_buffer = blob->content_begin();
_queue_begin = 0;
_queue_end = 0;
_number_of_stubs = 0;
}
StubQueue::~StubQueue() {
// Note: Currently StubQueues are never destroyed so nothing needs to be done here.
// If we want to implement the destructor, we need to release the BufferBlob
// allocated in the constructor (i.e., we need to keep it around or look it
// up via CodeCache::find_blob(...).
Unimplemented();
}
void StubQueue::deallocate_unused_tail() {
CodeBlob* blob = CodeCache::find_blob((void*)_stub_buffer);
CodeCache::free_unused_tail(blob, used_space());
// Update the limits to the new, trimmed CodeBlob size
_buffer_size = blob->content_size();
_buffer_limit = blob->content_size();
}
Stub* StubQueue::stub_containing(address pc) const {
if (contains(pc)) {
for (Stub* s = first(); s != NULL; s = next(s)) {
if (stub_contains(s, pc)) return s;
}
}
return NULL;
}
Stub* StubQueue::request_committed(int code_size) {
Stub* s = request(code_size);
if (s != NULL) commit(code_size);
return s;
}
int StubQueue::compute_stub_size(Stub* stub, int code_size) {
address stub_begin = (address) stub;
address code_begin = stub_code_begin(stub);
address code_end = align_up(code_begin + code_size, stub_alignment());
return (int)(code_end - stub_begin);
}
Stub* StubQueue::request(int requested_code_size) {
assert(requested_code_size > 0, "requested_code_size must be > 0");
if (_mutex != NULL) _mutex->lock_without_safepoint_check();
Stub* s = current_stub();
int requested_size = compute_stub_size(s, requested_code_size);
if (requested_size <= available_space()) {
if (is_contiguous()) {
// Queue: |...|XXXXXXX|.............|
// ^0 ^begin ^end ^size = limit
assert(_buffer_limit == _buffer_size, "buffer must be fully usable");
if (_queue_end + requested_size <= _buffer_size) {
// code fits in at the end => nothing to do
stub_initialize(s, requested_size);
return s;
} else {
// stub doesn't fit in at the queue end
// => reduce buffer limit & wrap around
assert(!is_empty(), "just checkin'");
_buffer_limit = _queue_end;
_queue_end = 0;
}
}
}
if (requested_size <= available_space()) {
assert(!is_contiguous(), "just checkin'");
assert(_buffer_limit <= _buffer_size, "queue invariant broken");
// Queue: |XXX|.......|XXXXXXX|.......|
// ^0 ^end ^begin ^limit ^size
s = current_stub();
stub_initialize(s, requested_size);
return s;
}
// Not enough space left
if (_mutex != NULL) _mutex->unlock();
return NULL;
}
void StubQueue::commit(int committed_code_size) {
assert(committed_code_size > 0, "committed_code_size must be > 0");
Stub* s = current_stub();
int committed_size = compute_stub_size(s, committed_code_size);
assert(committed_size <= stub_size(s), "committed size must not exceed requested size");
stub_initialize(s, committed_size);
_queue_end += committed_size;
_number_of_stubs++;
if (_mutex != NULL) _mutex->unlock();
debug_only(stub_verify(s);)
}
void StubQueue::remove_first() {
if (number_of_stubs() == 0) return;
Stub* s = first();
debug_only(stub_verify(s);)
stub_finalize(s);
_queue_begin += stub_size(s);
assert(_queue_begin <= _buffer_limit, "sanity check");
if (_queue_begin == _queue_end) {
// buffer empty
// => reset queue indices
_queue_begin = 0;
_queue_end = 0;
_buffer_limit = _buffer_size;
} else if (_queue_begin == _buffer_limit) {
// buffer limit reached
// => reset buffer limit & wrap around
_buffer_limit = _buffer_size;
_queue_begin = 0;
}
_number_of_stubs--;
}
void StubQueue::remove_first(int n) {
int i = MIN2(n, number_of_stubs());
while (i-- > 0) remove_first();
}
void StubQueue::remove_all(){
debug_only(verify();)
remove_first(number_of_stubs());
assert(number_of_stubs() == 0, "sanity check");
}
void StubQueue::verify() {
// verify only if initialized
if (_stub_buffer == NULL) return;
MutexLocker lock(_mutex, Mutex::_no_safepoint_check_flag);
// verify index boundaries
guarantee(0 <= _buffer_size, "buffer size must be positive");
guarantee(0 <= _buffer_limit && _buffer_limit <= _buffer_size , "_buffer_limit out of bounds");
guarantee(0 <= _queue_begin && _queue_begin < _buffer_limit, "_queue_begin out of bounds");
guarantee(0 <= _queue_end && _queue_end <= _buffer_limit, "_queue_end out of bounds");
// verify alignment
guarantee(_buffer_size % stub_alignment() == 0, "_buffer_size not aligned");
guarantee(_buffer_limit % stub_alignment() == 0, "_buffer_limit not aligned");
guarantee(_queue_begin % stub_alignment() == 0, "_queue_begin not aligned");
guarantee(_queue_end % stub_alignment() == 0, "_queue_end not aligned");
// verify buffer limit/size relationship
if (is_contiguous()) {
guarantee(_buffer_limit == _buffer_size, "_buffer_limit must equal _buffer_size");
}
// verify contents
int n = 0;
for (Stub* s = first(); s != NULL; s = next(s)) {
stub_verify(s);
n++;
}
guarantee(n == number_of_stubs(), "number of stubs inconsistent");
guarantee(_queue_begin != _queue_end || n == 0, "buffer indices must be the same");
}
void StubQueue::print() {
MutexLocker lock(_mutex, Mutex::_no_safepoint_check_flag);
for (Stub* s = first(); s != NULL; s = next(s)) {
stub_print(s);
}
}
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