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8374984: Convert workerUtils to use Atomic<T>

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Reviewed-by: shade, stefank
This commit is contained in:
Kim Barrett 2026-01-15 12:37:50 +00:00
parent f6e5c885e7
commit 8ad8920aae
2 changed files with 20 additions and 17 deletions
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25
src/hotspot/share/gc/shared/workerUtils.cpp
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2001, 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
@ -22,8 +22,9 @@
*
*/
#include "cppstdlib/new.hpp"
#include "gc/shared/workerUtils.hpp"
#include "runtime/atomicAccess.hpp"
#include "runtime/atomic.hpp"
#include "runtime/mutexLocker.hpp"
// *** WorkerThreadsBarrierSync
@ -80,21 +81,21 @@ void WorkerThreadsBarrierSync::abort() {
SubTasksDone::SubTasksDone(uint n) :
_tasks(nullptr), _n_tasks(n) {
_tasks = NEW_C_HEAP_ARRAY(bool, n, mtInternal);
_tasks = NEW_C_HEAP_ARRAY(Atomic<bool>, n, mtInternal);
for (uint i = 0; i < _n_tasks; i++) {
_tasks[i] = false;
::new (&_tasks[i]) Atomic<bool>(false);
}
}
#ifdef ASSERT
void SubTasksDone::all_tasks_claimed_impl(uint skipped[], size_t skipped_size) {
if (AtomicAccess::cmpxchg(&_verification_done, false, true)) {
if (!_verification_done.compare_set(false, true)) {
// another thread has done the verification
return;
}
// all non-skipped tasks are claimed
for (uint i = 0; i < _n_tasks; ++i) {
if (!_tasks[i]) {
if (!_tasks[i].load_relaxed()) {
auto is_skipped = false;
for (size_t j = 0; j < skipped_size; ++j) {
if (i == skipped[j]) {
@ -109,27 +110,27 @@ void SubTasksDone::all_tasks_claimed_impl(uint skipped[], size_t skipped_size) {
for (size_t i = 0; i < skipped_size; ++i) {
auto task_index = skipped[i];
assert(task_index < _n_tasks, "Array in range.");
assert(!_tasks[task_index], "%d is both claimed and skipped.", task_index);
assert(!_tasks[task_index].load_relaxed(), "%d is both claimed and skipped.", task_index);
}
}
#endif
bool SubTasksDone::try_claim_task(uint t) {
assert(t < _n_tasks, "bad task id.");
return !_tasks[t] && !AtomicAccess::cmpxchg(&_tasks[t], false, true);
return !_tasks[t].load_relaxed() && _tasks[t].compare_set(false, true);
}
SubTasksDone::~SubTasksDone() {
assert(_verification_done, "all_tasks_claimed must have been called.");
FREE_C_HEAP_ARRAY(bool, _tasks);
assert(_verification_done.load_relaxed(), "all_tasks_claimed must have been called.");
FREE_C_HEAP_ARRAY(Atomic<bool>, _tasks);
}
// *** SequentialSubTasksDone
bool SequentialSubTasksDone::try_claim_task(uint& t) {
t = _num_claimed;
t = _num_claimed.load_relaxed();
if (t < _num_tasks) {
t = AtomicAccess::add(&_num_claimed, 1u) - 1;
t = _num_claimed.fetch_then_add(1u);
}
return t < _num_tasks;
}

12
src/hotspot/share/gc/shared/workerUtils.hpp
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2002, 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
@ -28,6 +28,7 @@
#include "cppstdlib/type_traits.hpp"
#include "memory/allocation.hpp"
#include "metaprogramming/enableIf.hpp"
#include "runtime/atomic.hpp"
#include "runtime/mutex.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
@ -79,11 +80,11 @@ public:
// enumeration type.
class SubTasksDone: public CHeapObj<mtInternal> {
volatile bool* _tasks;
Atomic<bool>* _tasks;
uint _n_tasks;
// make sure verification logic is run exactly once to avoid duplicate assertion failures
DEBUG_ONLY(volatile bool _verification_done = false;)
DEBUG_ONLY(Atomic<bool> _verification_done;)
void all_tasks_claimed_impl(uint skipped[], size_t skipped_size) NOT_DEBUG_RETURN;
NONCOPYABLE(SubTasksDone);
@ -127,7 +128,7 @@ public:
class SequentialSubTasksDone : public CHeapObj<mtInternal> {
uint _num_tasks; // Total number of tasks available.
volatile uint _num_claimed; // Number of tasks claimed.
Atomic<uint> _num_claimed; // Number of tasks claimed.
NONCOPYABLE(SequentialSubTasksDone);
@ -135,7 +136,8 @@ public:
SequentialSubTasksDone(uint num_tasks) : _num_tasks(num_tasks), _num_claimed(0) { }
~SequentialSubTasksDone() {
// Claiming may try to claim more tasks than there are.
assert(_num_claimed >= _num_tasks, "Claimed %u tasks of %u", _num_claimed, _num_tasks);
assert(_num_claimed.load_relaxed() >= _num_tasks,
"Claimed %u tasks of %u", _num_claimed.load_relaxed(), _num_tasks);
}
// Attempt to claim the next unclaimed task in the sequence,