serenity/Kernel/Devices/AsyncDeviceRequest.cpp

/*
 * Copyright (c) 2020, The SerenityOS developers.
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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#include <Kernel/Devices/AsyncDeviceRequest.h>
#include <Kernel/Devices/Device.h>

namespace Kernel {

AsyncDeviceRequest::AsyncDeviceRequest(Device& device)
    : m_device(device)
    , m_process(*Process::current())
{
}

AsyncDeviceRequest::~AsyncDeviceRequest()
{
    {
        ScopedSpinLock lock(m_lock);
        ASSERT(is_completed_result(m_result));
        ASSERT(m_sub_requests_pending.is_empty());
    }

    // We should not need any locking here anymore. The destructor should
    // only be called until either wait() or cancel() (once implemented) returned.
    // At that point no sub-request should be adding more requests and all
    // sub-requests should be completed (either succeeded, failed, or cancelled).
    // Which means there should be no more pending sub-requests and the
    // entire AsyncDeviceRequest hirarchy should be immutable.
    for (auto& sub_request : m_sub_requests_complete) {
        ASSERT(is_completed_result(sub_request.m_result)); // Shouldn't need any locking anymore
        ASSERT(sub_request.m_parent_request == this);
        sub_request.m_parent_request = nullptr;
    }
}

void AsyncDeviceRequest::request_finished()
{
    if (m_parent_request)
        m_parent_request->sub_request_finished(*this);

    // Trigger processing the next request
    m_device.process_next_queued_request({}, *this);

    // Wake anyone who may be waiting
    m_queue.wake_all();
}

auto AsyncDeviceRequest::wait(timeval* timeout) -> RequestWaitResult
{
    ASSERT(!m_parent_request);
    auto request_result = get_request_result();
    if (is_completed_result(request_result))
        return { request_result, Thread::BlockResult::NotBlocked };
    auto wait_result = Thread::current()->wait_on(m_queue, name(), Thread::BlockTimeout(false, timeout));
    return { get_request_result(), wait_result };
}

auto AsyncDeviceRequest::get_request_result() const -> RequestResult
{
    ScopedSpinLock lock(m_lock);
    return m_result;
}

void AsyncDeviceRequest::add_sub_request(NonnullRefPtr<AsyncDeviceRequest> sub_request)
{
    // Sub-requests cannot be for the same device
    ASSERT(&m_device != &sub_request->m_device);
    ASSERT(sub_request->m_parent_request == nullptr);
    sub_request->m_parent_request = this;

    bool should_start;
    {
        ScopedSpinLock lock(m_lock);
        ASSERT(!is_completed_result(m_result));
        m_sub_requests_pending.append(sub_request);
        should_start = (m_result == Started);
    }
    if (should_start)
        sub_request->do_start();
}

void AsyncDeviceRequest::sub_request_finished(AsyncDeviceRequest& sub_request)
{
    bool all_completed;
    {
        ScopedSpinLock lock(m_lock);
        ASSERT(m_result == Started);
        size_t index;
        for (index = 0; index < m_sub_requests_pending.size(); index++) {
            if (&m_sub_requests_pending[index] == &sub_request) {
                NonnullRefPtr<AsyncDeviceRequest> request(m_sub_requests_pending[index]);
                m_sub_requests_pending.remove(index);
                m_sub_requests_complete.append(move(request));
                break;
            }
        }
        ASSERT(index < m_sub_requests_pending.size());
        all_completed = m_sub_requests_pending.is_empty();
        if (all_completed) {
            // Aggregate any errors
            bool any_failures = false;
            bool any_memory_faults = false;
            for (index = 0; index < m_sub_requests_complete.size(); index++) {
                auto& sub_request = m_sub_requests_complete[index];
                auto sub_result = sub_request.get_request_result();
                ASSERT(is_completed_result(sub_result));
                switch (sub_result) {
                case Failure:
                    any_failures = true;
                    break;
                case MemoryFault:
                    any_memory_faults = true;
                    break;
                default:
                    break;
                }
                if (any_failures && any_memory_faults)
                    break; // Stop checking if all error conditions were found
            }
            if (any_failures)
                m_result = Failure;
            else if (any_memory_faults)
                m_result = MemoryFault;
            else
                m_result = Success;
        }
    }
    if (all_completed)
        request_finished();
}

void AsyncDeviceRequest::complete(RequestResult result)
{
    ASSERT(result == Success || result == Failure || result == MemoryFault);
    ScopedCritical critical;
    {
        ScopedSpinLock lock(m_lock);
        ASSERT(m_result == Started);
        m_result = result;
    }
    if (Processor::current().in_irq()) {
        ref(); // Make sure we don't get freed
        Processor::deferred_call_queue([this]() {
            request_finished();
            unref();
        });
    } else {
        request_finished();
    }
}

}