110 lines
3.8 KiB
C++
110 lines
3.8 KiB
C++
// Copyright 2010-2025 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "ortools/util/solve_interrupter.h"
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#include <atomic>
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#include <optional>
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#include <utility>
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#include "absl/base/nullability.h"
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#include "absl/functional/any_invocable.h"
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#include "absl/synchronization/mutex.h"
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#include "ortools/base/linked_hash_map.h"
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#include "ortools/base/logging.h"
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namespace operations_research {
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void SolveInterrupter::Interrupt() {
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const absl::MutexLock lock(mutex_);
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// Here we don't use compare_exchange_strong since we need to hold the lock
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// before changing the value of interrupted_ anyway. So there is no need to
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// use this complex function.
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if (interrupted_.load()) {
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// We must not call the callbacks more than once.
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return;
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}
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// We need to change this value while holding the lock since in
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// AddInterruptionCallback() we must know if we need to call the new callback
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// of if this function has called it.
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interrupted_ = true;
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// We are holding the lock while calling callbacks. This makes it impossible
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// to call Interrupt(), AddInterruptionCallback(), or
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// RemoveInterruptionCallback() from a callback but it ensures that external
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// code that can modify callbacks_ will wait until the end of Interrupt.
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for (auto& [callback_id, callback] : callbacks_) {
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// We can only have nullptr if:
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// * interrupted_ was true when AddInterruptionCallback() was called,
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// * or a previous Interrupt() has set the pointer to null.
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// In these two cases we should not reach this code.
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CHECK(callback != nullptr);
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std::move(callback)();
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callback = nullptr;
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}
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}
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SolveInterrupter::CallbackId SolveInterrupter::AddInterruptionCallback(
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absl_nonnull Callback callback) const {
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const absl::MutexLock lock(mutex_);
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const CallbackId id = next_callback_id_;
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++next_callback_id_;
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const auto [it, inserted] = callbacks_.try_emplace(id, std::move(callback));
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CHECK(inserted);
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// We must make this call while holding the lock since we want to be sure that
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// the calls to the callbacks_ won't occur before we registered the new
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// one. If we were not holding the lock, this could return false and before we
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// could add the new callback to callbacks_, the Interrupt() function may
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// still have called them.
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if (interrupted_.load()) {
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std::move(it->second)();
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it->second = nullptr;
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}
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return id;
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}
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void SolveInterrupter::RemoveInterruptionCallback(CallbackId id) const {
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const absl::MutexLock lock(mutex_);
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CHECK_EQ(callbacks_.erase(id), 1) << "unregistered callback id: " << id;
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}
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ScopedSolveInterrupterCallback::ScopedSolveInterrupterCallback(
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const SolveInterrupter* absl_nullable const interrupter,
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absl_nonnull SolveInterrupter::Callback callback)
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: interrupter_(interrupter),
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callback_id_(
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interrupter != nullptr
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? std::make_optional(
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interrupter->AddInterruptionCallback(std::move(callback)))
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: std::nullopt) {}
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ScopedSolveInterrupterCallback::~ScopedSolveInterrupterCallback() {
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RemoveCallbackIfNecessary();
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}
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void ScopedSolveInterrupterCallback::RemoveCallbackIfNecessary() {
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if (callback_id_) {
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CHECK_NE(interrupter_, nullptr);
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interrupter_->RemoveInterruptionCallback(*callback_id_);
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callback_id_.reset();
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}
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}
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} // namespace operations_research
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