/*
 * Copyright (c) Likewise Software.  All rights Reserved.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the license, or (at
 * your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
 * General Public License for more details.  You should have received a copy
 * of the GNU Lesser General Public License along with this program.  If
 * not, see <http://www.gnu.org/licenses/>.
 *
 * LIKEWISE SOFTWARE MAKES THIS SOFTWARE AVAILABLE UNDER OTHER LICENSING
 * TERMS AS WELL.  IF YOU HAVE ENTERED INTO A SEPARATE LICENSE AGREEMENT
 * WITH LIKEWISE SOFTWARE, THEN YOU MAY ELECT TO USE THE SOFTWARE UNDER THE
 * TERMS OF THAT SOFTWARE LICENSE AGREEMENT INSTEAD OF THE TERMS OF THE GNU
 * LESSER GENERAL PUBLIC LICENSE, NOTWITHSTANDING THE ABOVE NOTICE.  IF YOU
 * HAVE QUESTIONS, OR WISHTO REQUEST A COPY OF THE ALTERNATE LICENSING
 * TERMS OFFERED BY LIKEWISE SOFTWARE, PLEASE CONTACT LIKEWISE SOFTWARE AT
 * license@likewisesoftware.com
 */

/*
 * Module Name:
 *
 *        threadpool-epoll.c
 *
 * Abstract:
 *
 *        Thread pool API (epoll backend)
 *
 * Authors: Brian Koropoff (bkoropoff@likewise.com)
 *
 */

#include "includes.h"
#include "threadpool-epoll.h"

/* FIXME: Make these tweakable on the thread pool itself */

/* Maximum events to read on each epoll_wait() */
#define MAX_EVENTS 500
/* Number of event-processing threads */
#define EVENT_THREAD_COUNT 8
/* Number of work item-processing threads */
#define WORK_THREAD_COUNT 8
/* Maximum number of ticks (task function invocations) to
   process each iteration of the event loop */
#define MAX_TICKS 1000

static
VOID
TaskDelete(
    PEPOLL_TASK pTask
    )
{
    RtlMemoryFree(pTask);
}

/*
 * Wakes up a thread.  Call with the thread lock held
 */
static
VOID
SignalThread(
    PEPOLL_THREAD pThread
    )
{
    char c = 0;
    int res = 0;

    if (!pThread->bSignalled)
    {
        res = write(pThread->SignalFds[1], &c, sizeof(c));
        assert(res == sizeof(c));
        pThread->bSignalled = TRUE;
    }
}

static
VOID
LockAllThreads(
    PLW_THREAD_POOL pPool
    )
{
    ULONG i = 0;

    for (i = 0; i < pPool->ulEventThreadCount; i++)
    {
        LOCK_THREAD(&pPool->pEventThreads[i]);
    }
}

static
VOID
UnlockAllThreads(
    PLW_THREAD_POOL pPool
    )
{
    ULONG i = 0;

    for (i = 0; i < pPool->ulEventThreadCount; i++)
    {
        UNLOCK_THREAD(&pPool->pEventThreads[i]);
    }
}

/*
 * Runs one tick of a task.
 */
static
VOID
RunTask(
    PEPOLL_TASK pTask,
    LONG64 llNow
    )
{
    LONG64 llNewTime = 0;

    /* If task had a deadline, set the time we pass into
       the function to the time remaining */
    if (pTask->llDeadline != 0)
    {
        llNewTime = pTask->llDeadline - llNow;

        if (llNewTime < 0)
        {
            llNewTime = 0;
        }
    }

    pTask->pfnFunc(
        pTask,
        pTask->pFuncContext,
        pTask->EventArgs,
        &pTask->EventWait,
        &llNewTime);

    /* Clear event arguments except sticky bits */
    pTask->EventArgs &= LW_TASK_EVENT_CANCEL;

    /* If the function gave us a valid time, update the task deadline */
    if (llNewTime != 0)
    {
        pTask->llDeadline = llNow + llNewTime;
    }
    else
    {
        pTask->llDeadline = 0;
    }
}

/*
 * Updates the epoll set with the events a task is waiting on.
 */
static
NTSTATUS
UpdateEventWait(
    PEPOLL_TASK pTask,
    int EpollFd
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    __uint32_t events = 0;
    struct epoll_event event;

    if (pTask->EventWait != pTask->EventLastWait)
    {
        if (pTask->EventWait & LW_TASK_EVENT_FD_READABLE)
        {
            events |= EPOLLIN;
        }

        if (pTask->EventWait & LW_TASK_EVENT_FD_WRITABLE)
        {
            events |= EPOLLOUT;
        }

        if (pTask->EventWait & LW_TASK_EVENT_FD_EXCEPTION)
        {
            events |= EPOLLERR;
        }

        if (events)
        {
            event.events = events | EPOLLET;
            event.data.ptr = pTask;

            if (epoll_ctl(EpollFd, EPOLL_CTL_MOD, pTask->Fd, &event) < 0)
            {
                status = LwErrnoToNtStatus(errno);
                GOTO_ERROR_ON_STATUS(status);
            }
        }

        pTask->EventLastWait = pTask->EventWait;
    }

error:

    return status;
}

/*
 * Updates the set events on tasks from epoll results and
 * schedules them to run.
 */
static
VOID
ScheduleWaitingTasks(
    struct epoll_event* pEvents,
    int eventCount,
    LONG64 llNow,
    PRING pRunnable,
    PBOOLEAN pbSignalled
    )
{
    PLW_TASK pTask = NULL;
    int i = 0;

    *pbSignalled = FALSE;

    for (i = 0; i < eventCount; i++)
    {
        pTask = (PLW_TASK) pEvents[i].data.ptr;

        if (!pTask)
        {
            /* Event was the thread signal fd becoming active */
            *pbSignalled = TRUE;
            continue;
        }

        if ((pEvents[i].events & (EPOLLIN | EPOLLHUP)) &&
            (pTask->EventWait & LW_TASK_EVENT_FD_READABLE))
        {
            pTask->EventArgs |= LW_TASK_EVENT_FD_READABLE;
        }

        if (pEvents[i].events & EPOLLOUT)
        {
            pTask->EventArgs |= LW_TASK_EVENT_FD_WRITABLE;
        }

        if ((pEvents[i].events & EPOLLERR) &&
            (pTask->EventWait & LW_TASK_EVENT_FD_EXCEPTION))
        {
            pTask->EventArgs |= LW_TASK_EVENT_FD_EXCEPTION;
        }

        /* If the task's deadline has expired, set the time event bit */
        if (pTask->EventWait & LW_TASK_EVENT_TIME &&
            pTask->llDeadline != 0 &&
            pTask->llDeadline <= llNow)
        {
            pTask->EventArgs |= LW_TASK_EVENT_TIME;
        }

        /* Schedule task to run if it has been triggered */
        if (pTask->EventWait & pTask->EventArgs)
        {
            RingRemove(&pTask->QueueRing);
            RingEnqueue(pRunnable, &pTask->QueueRing);
        }
    }
}

static
VOID
ScheduleTimedTasks(
    PRING pTimed,
    LONG64 llNow,
    PRING pRunnable
    )
{
    PLW_TASK pTask = NULL;
    PRING pRing = NULL;
    PRING pNext = NULL;

    for (pRing = pTimed->pNext; pRing != pTimed; pRing = pNext)
    {
        pNext = pRing->pNext;
        pTask = LW_STRUCT_FROM_FIELD(pRing, EPOLL_TASK, QueueRing);

        /* No more tasks in the queue are past the deadline
           since the queue is sorted */
        if (pTask->llDeadline > llNow)
        {
            break;
        }

        RingRemove(&pTask->QueueRing);
        RingEnqueue(pRunnable, &pTask->QueueRing);

        pTask->EventArgs |= LW_TASK_EVENT_TIME;
    }
}

static
VOID
InsertTimedQueue(
    PRING pTimed,
    PLW_TASK pInsert
    )
{
    PLW_TASK pTask = NULL;
    PRING pRing = NULL;

    /* Find the first task in the queue with a later deadline than the task to insert */
    for (pRing = pTimed->pNext; pRing != pTimed; pRing = pRing->pNext)
    {
        pTask = LW_STRUCT_FROM_FIELD(pRing, EPOLL_TASK, QueueRing);

        if (pTask->llDeadline > pInsert->llDeadline)
            break;
    }

    /* Insert the task */
    RingInsertBefore(pRing, &pInsert->QueueRing);
}

static
NTSTATUS
Poll(
    IN PCLOCK pClock,
    IN OUT PLONG64 pllNow,
    IN int EpollFd,
    OUT struct epoll_event* pEvents,
    IN int maxEvents,
    IN LONG64 llNextDeadline,
    OUT int* pReady
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    int ready = 0;
    int timeout = 0;

    do
    {
        if (llNextDeadline != 0)
        {
            /* Convert to timeout in milliseconds */
            timeout = (llNextDeadline - *pllNow) / 1000000ll;
            if (timeout < 0)
            {
                timeout = 0;
            }
        }
        else
        {
            timeout = -1;
        }

        ready = epoll_wait(EpollFd, pEvents, maxEvents, timeout);
        if (ready < 0 && errno == EINTR)
        {
            /* Update current time so the next timeout calculation is correct */
            status = ClockGetMonotonicTime(pClock, pllNow);
            GOTO_ERROR_ON_STATUS(status);
        }
    } while (ready < 0 && errno == EINTR);

    if (ready < 0)
    {
        status = LwErrnoToNtStatus(errno);
        GOTO_ERROR_ON_STATUS(status);
    }

    *pReady = ready;

error:

    return status;
}

static
NTSTATUS
ProcessRunnable(
    PEPOLL_THREAD pThread,
    PRING pRunnable,
    PRING pTimed,
    PRING pWaiting,
    LONG64 llNow
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    ULONG ulTicks = MAX_TICKS;
    PLW_TASK pTask = NULL;
    PLW_TASK_GROUP pGroup = NULL;
    PRING pRing = NULL;
    PRING pNext = NULL;

    /* We are guaranteed to run each task at least once.  If tasks remain
       on the runnable list by yielding, we will continue to run them
       all in a round robin until our ticks are depleted. */
    while (ulTicks && !RingIsEmpty(pRunnable))
    {
        for (pRing = pRunnable->pNext; pRing != pRunnable; pRing = pNext)
        {
            pNext = pRing->pNext;

            pTask = LW_STRUCT_FROM_FIELD(pRing, EPOLL_TASK, QueueRing);

            RunTask(pTask, llNow);

            if (ulTicks)
            {
                ulTicks--;
            }

            if (pTask->EventWait & LW_TASK_EVENT_YIELD)
            {
                /* Task is yielding.  Set its trigger arguments
                   to whatever it gave us (modulo INIT and CANCEL).
                   Leave it on the runnable list for the next iteration. */
                pTask->EventArgs =
                    (pTask->EventWait & ~LW_TASK_EVENT_INIT) |
                    (pTask->EventArgs & LW_TASK_EVENT_CANCEL);
            }
            else if (pTask->EventWait != LW_TASK_EVENT_COMPLETE)
            {
                /* Task is still waiting to be runnable, put in back in epoll set */
                status = UpdateEventWait(
                    pTask,
                    pThread->EpollFd
                    );
                GOTO_ERROR_ON_STATUS(status);

                RingRemove(&pTask->QueueRing);

                if (pTask->EventWait & LW_TASK_EVENT_TIME)
                {
                    /* If the task is waiting for a timeout, insert it into the timed queue */
                    InsertTimedQueue(pTimed, pTask);
                }
                else
                {
                    /* Otherwise, put it in the generic waiting queue */
                    RingEnqueue(pWaiting, &pTask->QueueRing);
                }
            }
            else
            {
                /* Task is complete */
                RingRemove(&pTask->QueueRing);

                /* Turn off any fd in the epoll set */
                if (pTask->Fd >= 0)
                {
                    status = LwRtlSetTaskFd(pTask, pTask->Fd, 0);
                    GOTO_ERROR_ON_STATUS(status);
                }

                LOCK_POOL(pThread->pPool);
                pThread->ulLoad--;
                UNLOCK_POOL(pThread->pPool);

                pGroup = pTask->pGroup;

                /* If task was in a task group, remove it and notify anyone waiting
                   on the group */
                if (pGroup)
                {
                    LOCK_GROUP(pGroup);
                    pTask->pGroup = NULL;
                    RingRemove(&pTask->GroupRing);
                    pthread_cond_broadcast(&pGroup->Event);
                    UNLOCK_GROUP(pGroup);
                }

                LOCK_THREAD(pThread);
                if (--pTask->ulRefCount)
                {
                    /* The task still has a reference, so mark it as completed
                       and notify anyone waiting on it */
                    pTask->EventSignal = TASK_COMPLETE_MASK;
                    pthread_cond_broadcast(&pThread->Event);
                    UNLOCK_THREAD(pThread);
                }
                else
                {
                    /* We held the last reference to the task, so delete it */
                    RingRemove(&pTask->SignalRing);
                    UNLOCK_THREAD(pThread);
                    TaskDelete(pTask);
                }
            }
        }
    }

error:

    return status;
}

static
VOID
ScheduleSignalled(
    PEPOLL_THREAD pThread,
    PRING pRunnable,
    PBOOLEAN pbShutdown
    )
{
    PRING pRing = NULL;
    PRING pNext = NULL;
    PLW_TASK pTask = NULL;
    char c = 0;
    int res = 0;

    LOCK_THREAD(pThread);

    if (pThread->bSignalled)
    {
        pThread->bSignalled = FALSE;

        res = read(pThread->SignalFds[0], &c, sizeof(c));
        assert(res == sizeof(c));

        /* Add all signalled tasks to the runnable list */
        for (pRing = pThread->Tasks.pNext; pRing != &pThread->Tasks; pRing = pNext)
        {
            pNext = pRing->pNext;
            pTask = LW_STRUCT_FROM_FIELD(pRing, EPOLL_TASK, SignalRing);

            RingRemove(&pTask->SignalRing);
            RingRemove(&pTask->QueueRing);

            if (pTask->EventSignal != TASK_COMPLETE_MASK)
            {
                RingEnqueue(pRunnable, &pTask->QueueRing);
                /* Transfer the signal bits into the event args */
                pTask->EventArgs |= pTask->EventSignal;
                pTask->EventSignal = 0;
            }
        }

        if (pThread->bShutdown && !*pbShutdown)
        {
            *pbShutdown = pThread->bShutdown;
        }
    }

    UNLOCK_THREAD(pThread);
}


static
NTSTATUS
EventLoop(
    PEPOLL_THREAD pThread
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    RING timed;
    RING runnable;
    RING waiting;
    CLOCK clock = {0};
    LONG64 llNow;
    LONG64 llNextDeadline;
    struct epoll_event events[MAX_EVENTS];
    int ready = 0;
    BOOLEAN bShutdown = FALSE;
    BOOLEAN bSignalled = FALSE;

    RingInit(&runnable);
    RingInit(&timed);
    RingInit(&waiting);

    for (;;)
    {
        /* Get current time for this iteration */
        status = ClockGetMonotonicTime(&clock, &llNow);
        GOTO_ERROR_ON_STATUS(status);

        /* Schedule any timed tasks that are have reached their deadline */
        ScheduleTimedTasks(
            &timed,
            llNow,
            &runnable);

        /* Schedule any waiting tasks that epoll indicated are ready
           and check if the thread received a signal */
        ScheduleWaitingTasks(
            events,
            ready,
            llNow,
            &runnable,
            &bSignalled);

        if (bSignalled)
        {
            /* Schedule explicitly-signalled tasks and check if we
               have been told to shut down */
            ScheduleSignalled(
                pThread,
                &runnable,
                &bShutdown);
        }

        /* Process runnable tasks */
        status = ProcessRunnable(
            pThread,
            &runnable,
            &timed,
            &waiting,
            llNow);
        GOTO_ERROR_ON_STATUS(status);

        if (!RingIsEmpty(&runnable))
        {
            /* If there are still runnable tasks, set the next deadline
               to now so we can check for other tasks becoming runnable but
               do not block in Poll() */
            llNextDeadline = llNow;
        }
        else if (!RingIsEmpty(&timed))
        {
            /* There are timed tasks, so set our next deadline to the
               deadline of the first task in the queue */
            llNextDeadline = LW_STRUCT_FROM_FIELD(timed.pNext, EPOLL_TASK, QueueRing)->llDeadline;
        }
        else if (!RingIsEmpty(&waiting) || !bShutdown)
        {
            /* There are waiting tasks or we are not shutting down, so poll indefinitely */
            llNextDeadline = 0;
        }
        else
        {
            /* We are shutting down and there are no remaining tasks, so leave */
            break;
        }

        /* Wait (or check) for activity */
        status = Poll(
            &clock,
            &llNow,
            pThread->EpollFd,
            events,
            MAX_EVENTS,
            llNextDeadline,
            &ready);
        GOTO_ERROR_ON_STATUS(status);
    }

error:

    return status;
}

static
PVOID
EventThread(
    PVOID pContext
    )
{
    EventLoop((PEPOLL_THREAD) pContext);

    return NULL;
}

static
NTSTATUS
WorkLoop(
    PWORK_ITEM_THREAD pThread
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    PRING pRing = NULL;
    PWORK_ITEM pItem = NULL;

    LOCK_POOL(pThread->pPool);

    for(;;)
    {
        while (!pThread->pPool->bShutdown && RingIsEmpty(&pThread->pPool->WorkItems))
        {
            pthread_cond_wait(&pThread->pPool->Event, &pThread->pPool->Lock);
        }

        if (pThread->pPool->bShutdown)
        {
            break;
        }

        RingDequeue(&pThread->pPool->WorkItems, &pRing);

        UNLOCK_POOL(pThread->pPool);

        pItem = LW_STRUCT_FROM_FIELD(pRing, WORK_ITEM, Ring);

        pItem->pfnFunc(pItem->pContext);
        RtlMemoryFree(pItem);

        LOCK_POOL(pThread->pPool);
    }

    UNLOCK_POOL(pThread->pPool);

    return status;
}

static
PVOID
WorkThread(
    PVOID pContext
    )
{
    WorkLoop((PWORK_ITEM_THREAD) pContext);

    return NULL;
}

NTSTATUS
LwRtlCreateTask(
    PLW_THREAD_POOL pPool,
    PLW_TASK* ppTask,
    PLW_TASK_GROUP pGroup,
    LW_TASK_FUNCTION pfnFunc,
    PVOID pContext
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    PEPOLL_TASK pTask = NULL;
    PEPOLL_THREAD pThread = NULL;
    ULONG ulMinLoad = 0xFFFFFFFF;
    ULONG ulIndex = 0;

    status = LW_RTL_ALLOCATE_AUTO(&pTask);
    GOTO_ERROR_ON_STATUS(status);

    RingInit(&pTask->GroupRing);
    RingInit(&pTask->QueueRing);
    RingInit(&pTask->SignalRing);
    pTask->pGroup = pGroup;
    pTask->ulRefCount = 2;
    pTask->pfnFunc = pfnFunc;
    pTask->pFuncContext = pContext;
    pTask->Fd = -1;
    pTask->EventArgs = LW_TASK_EVENT_INIT;
    pTask->EventWait = LW_TASK_EVENT_EXPLICIT;
    pTask->llDeadline = 0;

    LOCK_POOL(pPool);

    for (ulIndex = 0; ulIndex < pPool->ulEventThreadCount; ulIndex++)
    {
        if (pPool->pEventThreads[ulIndex].ulLoad < ulMinLoad)
        {
            pThread = &pPool->pEventThreads[ulIndex];
            ulMinLoad = pThread->ulLoad;
        }
    }

    pThread->ulLoad++;

    UNLOCK_POOL(pPool);

    pTask->pThread = pThread;

    if (pGroup)
    {
        LOCK_GROUP(pGroup);
        RingInsertBefore(&pGroup->Tasks, &pTask->GroupRing);
        UNLOCK_GROUP(pGroup);
    }

    *ppTask = pTask;

error:

    return status;
}

NTSTATUS
LwRtlCreateTaskGroup(
    PLW_THREAD_POOL pPool,
    PLW_TASK_GROUP* ppGroup
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    PLW_TASK_GROUP pGroup = NULL;

    status = LW_RTL_ALLOCATE_AUTO(&pGroup);
    GOTO_ERROR_ON_STATUS(status);

    status = LwErrnoToNtStatus(pthread_mutex_init(&pGroup->Lock, NULL));
    GOTO_ERROR_ON_STATUS(status);

    status = LwErrnoToNtStatus(pthread_cond_init(&pGroup->Event, NULL));
    GOTO_ERROR_ON_STATUS(status);

    RingInit(&pGroup->Tasks);
    pGroup->pPool = pPool;

    *ppGroup = pGroup;

error:

    return status;
}

VOID
LwRtlReleaseTask(
    PLW_TASK* ppTask
    )
{
    PLW_TASK pTask = *ppTask;
    int ulRefCount = 0;

    if (pTask)
    {
        LOCK_THREAD(pTask->pThread);
        ulRefCount = --pTask->ulRefCount;
        if (ulRefCount == 0)
        {
            RingRemove(&pTask->SignalRing);
        }
        UNLOCK_THREAD(pTask->pThread);

        if (ulRefCount == 0)
        {
            TaskDelete(pTask);
        }

        *ppTask = NULL;
    }
}

VOID
LwRtlFreeTaskGroup(
    PLW_TASK_GROUP* ppGroup
    )
{
    PLW_TASK_GROUP pGroup = *ppGroup;

    if (pGroup)
    {
        pthread_mutex_destroy(&pGroup->Lock);
        pthread_cond_destroy(&pGroup->Event);
        RtlMemoryFree(pGroup);

        *ppGroup = NULL;
    }
}

LW_NTSTATUS
LwRtlSetTaskFd(
    PLW_TASK pTask,
    int Fd,
    LW_TASK_EVENT_MASK Mask
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    struct epoll_event event;

    memset(&event, 0, sizeof(event));

    if (Fd < 0)
    {
        status = STATUS_INVALID_HANDLE;
        GOTO_ERROR_ON_STATUS(status);
    }

    if (Fd == pTask->Fd)
    {
        if (Mask == 0)
        {
            if (epoll_ctl(pTask->pThread->EpollFd, EPOLL_CTL_DEL, pTask->Fd, &event) < 0)
            {
                status = LwErrnoToNtStatus(status);
                GOTO_ERROR_ON_STATUS(status);
            }

            pTask->Fd = -1;
        }
    }
    else
    {
        if (pTask->Fd >= 0)
        {
            /* Only one fd is supported */
            status = STATUS_INSUFFICIENT_RESOURCES;
            GOTO_ERROR_ON_STATUS(status);
        }

        pTask->Fd = Fd;

        if (epoll_ctl(pTask->pThread->EpollFd, EPOLL_CTL_ADD, pTask->Fd, &event) < 0)
        {
            status = LwErrnoToNtStatus(status);
            GOTO_ERROR_ON_STATUS(status);
        }
    }

error:

    return status;
}

NTSTATUS
LwRtlQueryTaskFd(
    PLW_TASK pTask,
    int Fd,
    PLW_TASK_EVENT_MASK pMask
    )
{
    NTSTATUS status = STATUS_SUCCESS;

    if (Fd < 0 || Fd != pTask->Fd)
    {
        status = STATUS_INVALID_HANDLE;
        GOTO_ERROR_ON_STATUS(status);
    }

    *pMask = pTask->EventArgs &
        (LW_TASK_EVENT_FD_READABLE |
         LW_TASK_EVENT_FD_WRITABLE |
         LW_TASK_EVENT_FD_EXCEPTION);

cleanup:

    return status;

error:

    *pMask = 0;

    goto cleanup;
}

VOID
LwRtlWakeTask(
    PLW_TASK pTask
    )
{
    LOCK_THREAD(pTask->pThread);

    if (pTask->EventSignal != TASK_COMPLETE_MASK)
    {
        pTask->EventSignal |= LW_TASK_EVENT_EXPLICIT;
        RingRemove(&pTask->SignalRing);
        RingEnqueue(&pTask->pThread->Tasks, &pTask->SignalRing);
        SignalThread(pTask->pThread);
    }

    UNLOCK_THREAD(pTask->pThread);
}

VOID
LwRtlCancelTask(
    PLW_TASK pTask
    )
{
    LOCK_THREAD(pTask->pThread);

    if (pTask->EventSignal != TASK_COMPLETE_MASK)
    {
        pTask->EventSignal |= LW_TASK_EVENT_EXPLICIT | LW_TASK_EVENT_CANCEL;
        RingRemove(&pTask->SignalRing);
        RingEnqueue(&pTask->pThread->Tasks, &pTask->SignalRing);
        SignalThread(pTask->pThread);
    }

    UNLOCK_THREAD(pTask->pThread);
}

VOID
LwRtlWaitTask(
    PLW_TASK pTask
    )
{
    LOCK_THREAD(pTask->pThread);

    while (pTask->EventSignal != TASK_COMPLETE_MASK)
    {
        pthread_cond_wait(&pTask->pThread->Event, &pTask->pThread->Lock);
    }

    UNLOCK_THREAD(pTask->pThread);
}

VOID
LwRtlWakeTaskGroup(
    PLW_TASK_GROUP pGroup
    )
{
    PRING ring = NULL;
    PLW_TASK pTask = NULL;

    LOCK_GROUP(pGroup);
    LockAllThreads(pGroup->pPool);

    for (ring = pGroup->Tasks.pNext; ring != &pGroup->Tasks; ring = ring->pNext)
    {
        pTask = LW_STRUCT_FROM_FIELD(ring, EPOLL_TASK, GroupRing);

        if (pTask->EventSignal != TASK_COMPLETE_MASK)
        {
            pTask->EventSignal |= LW_TASK_EVENT_EXPLICIT;
            RingRemove(&pTask->SignalRing);
            RingEnqueue(&pTask->pThread->Tasks, &pTask->SignalRing);
            SignalThread(pTask->pThread);
        }
    }

    UnlockAllThreads(pGroup->pPool);
    UNLOCK_GROUP(pGroup);
}

VOID
LwRtlCancelTaskGroup(
    PLW_TASK_GROUP pGroup
    )
{
    PRING ring = NULL;
    PLW_TASK pTask = NULL;

    LOCK_GROUP(pGroup);
    LockAllThreads(pGroup->pPool);

    for (ring = pGroup->Tasks.pNext; ring != &pGroup->Tasks; ring = ring->pNext)
    {
        pTask = LW_STRUCT_FROM_FIELD(ring, EPOLL_TASK, GroupRing);

        if (pTask->EventSignal != TASK_COMPLETE_MASK)
        {
            pTask->EventSignal |= LW_TASK_EVENT_EXPLICIT | LW_TASK_EVENT_CANCEL;
            RingRemove(&pTask->SignalRing);
            RingEnqueue(&pTask->pThread->Tasks, &pTask->SignalRing);
            SignalThread(pTask->pThread);
        }
    }

    UnlockAllThreads(pGroup->pPool);
    UNLOCK_GROUP(pGroup);
}

VOID
LwRtlWaitTaskGroup(
    PLW_TASK_GROUP pGroup
    )
{
    PRING pRing = NULL;
    PLW_TASK pTask = NULL;
    BOOLEAN bStillAlive = TRUE;

    LOCK_GROUP(pGroup);

    while (bStillAlive)
    {
        bStillAlive = FALSE;

        LockAllThreads(pGroup->pPool);

        for (pRing = pGroup->Tasks.pNext; !bStillAlive && pRing != &pGroup->Tasks; pRing = pRing->pNext)
        {
            pTask = LW_STRUCT_FROM_FIELD(pRing, EPOLL_TASK, GroupRing);

            if (pTask->EventSignal != TASK_COMPLETE_MASK)
            {
                bStillAlive = TRUE;
            }
        }

        UnlockAllThreads(pGroup->pPool);

        if (bStillAlive)
        {
            pthread_cond_wait(&pGroup->Event, &pGroup->Lock);
        }
    }

    UNLOCK_GROUP(pGroup);
}

static
NTSTATUS
InitEventThread(
    PEPOLL_POOL pPool,
    PEPOLL_THREAD pThread,
    LONG lCpu
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    struct epoll_event event;
    cpu_set_t cpuSet;
    pthread_attr_t threadAttr;
    BOOLEAN bThreadAttrInit = FALSE;

    status = LwErrnoToNtStatus(pthread_attr_init(&threadAttr));
    GOTO_ERROR_ON_STATUS(status);
    bThreadAttrInit = TRUE;

    CPU_ZERO(&cpuSet);

    pThread->pPool = pPool;

    status = LwErrnoToNtStatus(pthread_mutex_init(&pThread->Lock, NULL));
    GOTO_ERROR_ON_STATUS(status);

    status = LwErrnoToNtStatus(pthread_cond_init(&pThread->Event, NULL));
    GOTO_ERROR_ON_STATUS(status);

    if (pipe(pThread->SignalFds) < 0)
    {
        status = LwErrnoToNtStatus(errno);
        GOTO_ERROR_ON_STATUS(status);
    }

    if ((pThread->EpollFd = epoll_create(MAX_EVENTS)) < 0)
    {
        status = LwErrnoToNtStatus(errno);
        GOTO_ERROR_ON_STATUS(status);
    }

    /* Add signal fd to epoll set */
    event.events = EPOLLIN;
    event.data.ptr = NULL;

    if (epoll_ctl(pThread->EpollFd, EPOLL_CTL_ADD, pThread->SignalFds[0], &event) < 0)
    {
        status = LwErrnoToNtStatus(errno);
        GOTO_ERROR_ON_STATUS(status);
    }

    RingInit(&pThread->Tasks);

    if (lCpu >= 0)
    {
        CPU_SET((int) lCpu, &cpuSet);

        status = LwErrnoToNtStatus(
            pthread_attr_setaffinity_np(
                &threadAttr,
                sizeof(cpuSet),
                &cpuSet));
        GOTO_ERROR_ON_STATUS(status);
    }

    status = LwErrnoToNtStatus(
        pthread_create(
            &pThread->Thread,
            &threadAttr,
            EventThread,
            pThread));
    GOTO_ERROR_ON_STATUS(status);

error:

    if (bThreadAttrInit)
    {
        pthread_attr_destroy(&threadAttr);
    }

    return status;
}

static
VOID
DestroyEventThread(
    PEPOLL_THREAD pThread
    )
{
    pthread_mutex_destroy(&pThread->Lock);
    pthread_cond_destroy(&pThread->Event);

    if (pThread->EpollFd >= 0)
    {
        close(pThread->EpollFd);
    }

    if (pThread->SignalFds[0] >= 0)
    {
        close(pThread->SignalFds[0]);
    }

    if (pThread->SignalFds[1] >= 0)
    {
        close(pThread->SignalFds[1]);
    }
}

static
NTSTATUS
InitWorkThread(
    PEPOLL_POOL pPool,
    PWORK_ITEM_THREAD pThread
    )
{
    NTSTATUS status = STATUS_SUCCESS;

    pThread->pPool = pPool;

    status = pthread_create(
        &pThread->Thread,
        NULL,
        WorkThread,
        pThread);
    GOTO_ERROR_ON_STATUS(status);

error:

    return status;
}

NTSTATUS
LwRtlCreateThreadPool(
    PLW_THREAD_POOL* ppPool
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    PLW_THREAD_POOL pPool = NULL;
    int i = 0;
    int numCpus = 0;

    status = LW_RTL_ALLOCATE_AUTO(&pPool);
    GOTO_ERROR_ON_STATUS(status);

    RingInit(&pPool->WorkItems);

    status = LwErrnoToNtStatus(pthread_mutex_init(&pPool->Lock, NULL));
    GOTO_ERROR_ON_STATUS(status);

    status = LwErrnoToNtStatus(pthread_cond_init(&pPool->Event, NULL));
    GOTO_ERROR_ON_STATUS(status);

    numCpus = sysconf(_SC_NPROCESSORS_ONLN);

    if (numCpus < 0)
    {
        pPool->ulEventThreadCount = EVENT_THREAD_COUNT;
    }
    else
    {
        pPool->ulEventThreadCount = (ULONG) numCpus;
    }

    status = LW_RTL_ALLOCATE_ARRAY_AUTO(
        &pPool->pEventThreads,
        pPool->ulEventThreadCount);
    GOTO_ERROR_ON_STATUS(status);

    for (i = 0; i < pPool->ulEventThreadCount; i++)
    {
        status = InitEventThread(pPool, &pPool->pEventThreads[i], numCpus >= 0 ? i % numCpus : -1);
        GOTO_ERROR_ON_STATUS(status);
    }

    pPool->ulWorkThreadCount = WORK_THREAD_COUNT;

    status = LW_RTL_ALLOCATE_ARRAY_AUTO(
        &pPool->pWorkThreads,
        pPool->ulWorkThreadCount);
    GOTO_ERROR_ON_STATUS(status);

    for (i = 0; i < pPool->ulWorkThreadCount; i++)
    {
        status = InitWorkThread(pPool, &pPool->pWorkThreads[i]);
        GOTO_ERROR_ON_STATUS(status);
    }

    pPool->ulRefCount = 1;

    *ppPool = pPool;

error:

    return status;
}

VOID
LwRtlFreeThreadPool(
    PLW_THREAD_POOL* ppPool
    )
{
    PLW_THREAD_POOL pPool = *ppPool;
    PEPOLL_THREAD pThread = NULL;
    int i = 0;

    if (pPool)
    {
        LOCK_POOL(pPool);
        pPool->bShutdown = TRUE;
        pthread_cond_broadcast(&pPool->Event);
        UNLOCK_POOL(pPool);

        if (pPool->pEventThreads)
        {
            for (i = 0; i < pPool->ulEventThreadCount; i++)
            {
                pThread = &pPool->pEventThreads[i];
                LOCK_THREAD(pThread);
                pThread->bShutdown = TRUE;
                SignalThread(pThread);
                UNLOCK_THREAD(pThread);
                pthread_join(pThread->Thread, NULL);
                DestroyEventThread(pThread);
            }

            RtlMemoryFree(pPool->pEventThreads);
        }

        if (pPool->pWorkThreads)
        {
            for (i = 0; i < pPool->ulWorkThreadCount; i++)
            {
                pthread_join(pPool->pWorkThreads[i].Thread, NULL);
            }

            RtlMemoryFree(pPool->pWorkThreads);
        }

        pthread_mutex_destroy(&pPool->Lock);

        RtlMemoryFree(pPool);

        *ppPool = NULL;
    }
}

NTSTATUS
LwRtlQueueWorkItem(
    PLW_THREAD_POOL pPool,
    LW_WORK_ITEM_FUNCTION pfnFunc,
    PVOID pContext,
    LW_WORK_ITEM_FLAGS Flags
    )
{
    NTSTATUS status = STATUS_SUCCESS;
    PWORK_ITEM pItem = NULL;

    status = LW_RTL_ALLOCATE_AUTO(&pItem);
    GOTO_ERROR_ON_STATUS(status);

    RingInit(&pItem->Ring);
    pItem->pfnFunc = pfnFunc;
    pItem->pContext = pContext;

    LOCK_POOL(pPool);

    RingEnqueue(&pPool->WorkItems, &pItem->Ring);
    pthread_cond_signal(&pPool->Event);
    pItem = NULL;

error:

    UNLOCK_POOL(pPool);

    if (pItem)
    {
        RtlMemoryFree(pItem);
    }

    return status;
}