eb51b70e6d
They only need to access the _vec_lock rwlock so mark it as mutable, but otherwise they provide a const interface to the calls, as the called func receives the entries by value and it cannot modify them. Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
69 lines
2.1 KiB
C++
69 lines
2.1 KiB
C++
/*
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* Copyright (C) 2020-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <seastar/core/rwlock.hh>
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#include <seastar/util/defer.hh>
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#include <seastar/util/noncopyable_function.hh>
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#include <seastar/core/coroutine.hh>
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#include <vector>
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// This class supports atomic removes (by using a lock and returning a
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// future) and non atomic insert and iteration (by using indexes).
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template <typename T>
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class atomic_vector {
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std::vector<T> _vec;
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mutable seastar::rwlock _vec_lock;
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public:
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void add(const T& value) {
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_vec.push_back(value);
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}
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seastar::future<> remove(const T& value) {
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return with_lock(_vec_lock.for_write(), [this, value] {
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_vec.erase(std::remove(_vec.begin(), _vec.end(), value), _vec.end());
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});
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}
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// This must be called on a thread. The callback function must not
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// call remove.
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//
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// We would take callbacks that take a T&, but we had bugs in the
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// past with some of those callbacks holding that reference past a
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// preemption.
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void thread_for_each(seastar::noncopyable_function<void(T)> func) const {
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_vec_lock.for_read().lock().get();
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auto unlock = seastar::defer([this] {
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_vec_lock.for_read().unlock();
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});
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// We grab a lock in remove(), but not in add(), so we
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// iterate using indexes to guard against the vector being
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// reallocated.
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for (size_t i = 0, n = _vec.size(); i < n; ++i) {
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func(_vec[i]);
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}
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}
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// The callback function must not call remove.
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//
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// We would take callbacks that take a T&, but we had bugs in the
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// past with some of those callbacks holding that reference past a
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// preemption.
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seastar::future<> for_each(seastar::noncopyable_function<seastar::future<>(T)> func) const {
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auto holder = co_await _vec_lock.hold_read_lock();
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// We grab a lock in remove(), but not in add(), so we
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// iterate using indexes to guard against the vector being
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// reallocated.
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for (size_t i = 0, n = _vec.size(); i < n; ++i) {
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co_await func(_vec[i]);
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}
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}
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};
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