mirror of
https://github.com/scylladb/scylladb.git
synced 2026-04-20 00:20:47 +00:00
90 lines
3.2 KiB
C++
90 lines
3.2 KiB
C++
/*
|
|
* Copyright (C) 2020-present ScyllaDB
|
|
*/
|
|
|
|
/*
|
|
* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "utils/on_internal_error.hh"
|
|
#include <seastar/core/rwlock.hh>
|
|
#include <seastar/util/defer.hh>
|
|
#include <seastar/util/noncopyable_function.hh>
|
|
|
|
#include <vector>
|
|
|
|
// This class supports atomic removes (by using a lock and returning a
|
|
// future) and non atomic insert and iteration (by using indexes).
|
|
template <typename T>
|
|
class atomic_vector {
|
|
std::vector<T> _vec;
|
|
mutable seastar::rwlock _vec_lock;
|
|
|
|
public:
|
|
void add(const T& value) {
|
|
_vec.push_back(value);
|
|
}
|
|
seastar::future<> remove(const T& value) {
|
|
return with_lock(_vec_lock.for_write(), [this, value] {
|
|
_vec.erase(std::remove(_vec.begin(), _vec.end(), value), _vec.end());
|
|
});
|
|
}
|
|
|
|
// This must be called on a thread. The callback function must not
|
|
// call remove or thread_for_each. If the callback function needs to
|
|
// call this, use thread_for_each_nested instead.
|
|
//
|
|
// We would take callbacks that take a T&, but we had bugs in the
|
|
// past with some of those callbacks holding that reference past a
|
|
// preemption.
|
|
void thread_for_each(seastar::noncopyable_function<void(T)> func) const {
|
|
_vec_lock.for_read().lock().get();
|
|
auto unlock = seastar::defer([this] {
|
|
_vec_lock.for_read().unlock();
|
|
});
|
|
// We grab a lock in remove(), but not in add(), so we
|
|
// iterate using indexes to guard against the vector being
|
|
// reallocated.
|
|
for (size_t i = 0, n = _vec.size(); i < n; ++i) {
|
|
func(_vec[i]);
|
|
}
|
|
}
|
|
|
|
// This must be called on a thread. This should be used only from
|
|
// the context of a thread_for_each callback, when the read lock is
|
|
// already held. The callback function must not call remove or
|
|
// thread_for_each.
|
|
void thread_for_each_nested(seastar::noncopyable_function<void(T)> func) const {
|
|
// When called in the context of thread_for_each, the read lock is
|
|
// already held, so we don't need to acquire it again. Acquiring it
|
|
// again could lead to a deadlock.
|
|
if (!_vec_lock.locked()) {
|
|
utils::on_internal_error("thread_for_each_nested called without holding the vector lock");
|
|
}
|
|
|
|
// We grab a lock in remove(), but not in add(), so we
|
|
// iterate using indexes to guard against the vector being
|
|
// reallocated.
|
|
for (size_t i = 0, n = _vec.size(); i < n; ++i) {
|
|
func(_vec[i]);
|
|
}
|
|
}
|
|
|
|
// The callback function must not call remove.
|
|
//
|
|
// We would take callbacks that take a T&, but we had bugs in the
|
|
// past with some of those callbacks holding that reference past a
|
|
// preemption.
|
|
seastar::future<> for_each(seastar::noncopyable_function<seastar::future<>(T)> func) const {
|
|
auto holder = co_await _vec_lock.hold_read_lock();
|
|
// We grab a lock in remove(), but not in add(), so we
|
|
// iterate using indexes to guard against the vector being
|
|
// reallocated.
|
|
for (size_t i = 0, n = _vec.size(); i < n; ++i) {
|
|
co_await func(_vec[i]);
|
|
}
|
|
}
|
|
};
|