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8374681: ZGC: Convert zJNICritical to use Atomic<T>

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Reviewed-by: tschatzl, stefank
This commit is contained in:
Axel Boldt-Christmas 2026-01-26 14:45:24 +00:00
parent b59f49a1c3
commit 61b722d59a
2 changed files with 20 additions and 20 deletions
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33
src/hotspot/share/gc/z/zJNICritical.cpp
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2021, 2026, 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
@ -24,7 +24,6 @@
#include "gc/z/zJNICritical.hpp"
#include "gc/z/zLock.inline.hpp"
#include "gc/z/zStat.hpp"
#include "runtime/atomicAccess.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/thread.inline.hpp"
#include "utilities/debug.hpp"
@ -46,22 +45,22 @@
static const ZStatCriticalPhase ZCriticalPhaseJNICriticalStall("JNI Critical Stall", false /* verbose */);
volatile int64_t ZJNICritical::_count;
ZConditionLock* ZJNICritical::_lock;
Atomic<int64_t> ZJNICritical::_count;
ZConditionLock* ZJNICritical::_lock;
void ZJNICritical::initialize() {
_count = 0;
precond(_count.load_relaxed() == 0);
_lock = new ZConditionLock();
}
void ZJNICritical::block() {
for (;;) {
const int64_t count = AtomicAccess::load_acquire(&_count);
const int64_t count = _count.load_acquire();
if (count < 0) {
// Already blocked, wait until unblocked
ZLocker<ZConditionLock> locker(_lock);
while (AtomicAccess::load_acquire(&_count) < 0) {
while (_count.load_acquire() < 0) {
_lock->wait();
}
@ -70,7 +69,7 @@ void ZJNICritical::block() {
}
// Increment and invert count
if (AtomicAccess::cmpxchg(&_count, count, -(count + 1)) != count) {
if (!_count.compare_set(count, -(count + 1))) {
continue;
}
@ -80,7 +79,7 @@ void ZJNICritical::block() {
if (count != 0) {
// Wait until blocked
ZLocker<ZConditionLock> locker(_lock);
while (AtomicAccess::load_acquire(&_count) != -1) {
while (_count.load_acquire() != -1) {
_lock->wait();
}
}
@ -91,18 +90,18 @@ void ZJNICritical::block() {
}
void ZJNICritical::unblock() {
const int64_t count = AtomicAccess::load_acquire(&_count);
const int64_t count = _count.load_acquire();
assert(count == -1, "Invalid count");
// Notify unblocked
ZLocker<ZConditionLock> locker(_lock);
AtomicAccess::release_store(&_count, (int64_t)0);
_count.release_store(0);
_lock->notify_all();
}
void ZJNICritical::enter_inner(JavaThread* thread) {
for (;;) {
const int64_t count = AtomicAccess::load_acquire(&_count);
const int64_t count = _count.load_acquire();
if (count < 0) {
// Wait until unblocked
@ -112,7 +111,7 @@ void ZJNICritical::enter_inner(JavaThread* thread) {
ThreadBlockInVM tbivm(thread);
ZLocker<ZConditionLock> locker(_lock);
while (AtomicAccess::load_acquire(&_count) < 0) {
while (_count.load_acquire() < 0) {
_lock->wait();
}
@ -121,7 +120,7 @@ void ZJNICritical::enter_inner(JavaThread* thread) {
}
// Increment count
if (AtomicAccess::cmpxchg(&_count, count, count + 1) != count) {
if (!_count.compare_set(count, count + 1)) {
continue;
}
@ -142,17 +141,17 @@ void ZJNICritical::enter(JavaThread* thread) {
void ZJNICritical::exit_inner() {
for (;;) {
const int64_t count = AtomicAccess::load_acquire(&_count);
const int64_t count = _count.load_acquire();
assert(count != 0, "Invalid count");
if (count > 0) {
// No block in progress, decrement count
if (AtomicAccess::cmpxchg(&_count, count, count - 1) != count) {
if (!_count.compare_set(count, count - 1)) {
continue;
}
} else {
// Block in progress, increment count
if (AtomicAccess::cmpxchg(&_count, count, count + 1) != count) {
if (!_count.compare_set(count, count + 1)) {
continue;
}

7
src/hotspot/share/gc/z/zJNICritical.hpp
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2021, 2026, 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
@ -25,14 +25,15 @@
#define SHARE_GC_Z_ZJNICRITICAL_HPP
#include "memory/allocation.hpp"
#include "runtime/atomic.hpp"
class JavaThread;
class ZConditionLock;
class ZJNICritical : public AllStatic {
private:
static volatile int64_t _count;
static ZConditionLock* _lock;
static Atomic<int64_t> _count;
static ZConditionLock* _lock;
static void enter_inner(JavaThread* thread);
static void exit_inner();