cmds/lshal/Timeout.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <chrono>
#include <future>

#include <hidl/Status.h>
#include <utils/Errors.h>

namespace android {
namespace lshal {

// Call function on interfaceObject and wait for result until the given timeout has reached.
// Callback functions pass to timeoutIPC() may be executed after the this function
// has returned, especially if deadline has been reached. Hence, care must be taken when passing
// data between the background thread and the main thread. See b/311143089.
template<class R, class P, class Function, class I, class... Args>
typename std::invoke_result<Function, I *, Args...>::type
timeoutIPC(std::chrono::duration<R, P> wait, const sp<I> &interfaceObject, Function &&func,
           Args &&... args) {
    using ::android::hardware::Status;

    // Execute on a background thread but do not defer execution.
    auto future =
            std::async(std::launch::async, func, interfaceObject, std::forward<Args>(args)...);
    auto status = future.wait_for(wait);
    if (status == std::future_status::ready) {
        return future.get();
    }

    // This future belongs to a background thread that we no longer care about.
    // Putting this in the global list avoids std::future::~future() that may wait for the
    // result to come back.
    // This leaks memory, but lshal is a debugging tool, so this is fine.
    static std::vector<decltype(future)> gDeadPool{};
    gDeadPool.emplace_back(std::move(future));

    if (status == std::future_status::timeout) {
        return Status::fromStatusT(TIMED_OUT);
    }
    return Status::fromExceptionCode(Status::Exception::EX_ILLEGAL_STATE, "Illegal future_status");
}
} // namespace lshal
} // namespace android