/* signal_node.c               -*-C-*-
 *
 *************************************************************************
 *
 *  Copyright (C) 2011-2016, Intel Corporation
 *  All rights reserved.
 *  
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
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 *      notice, this list of conditions and the following disclaimer.
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 *      notice, this list of conditions and the following disclaimer in
 *      the documentation and/or other materials provided with the
 *      distribution.
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 *      contributors may be used to endorse or promote products derived
 *      from this software without specific prior written permission.
 *  
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 *  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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 *  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 *  WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *  
 *  *********************************************************************
 *  
 *  PLEASE NOTE: This file is a downstream copy of a file mainitained in
 *  a repository at cilkplus.org. Changes made to this file that are not
 *  submitted through the contribution process detailed at
 *  http://www.cilkplus.org/submit-cilk-contribution will be lost the next
 *  time that a new version is released. Changes only submitted to the
 *  GNU compiler collection or posted to the git repository at
 *  https://bitbucket.org/intelcilkruntime/intel-cilk-runtime.git are
 *  not tracked.
 *  
 *  We welcome your contributions to this open source project. Thank you
 *  for your assistance in helping us improve Cilk Plus.
 *
 **************************************************************************/

#include "signal_node.h"
#include <stdlib.h>

/* Define cilk_semaphore_t for all of the respective systems. */
#if defined __APPLE__
#   include <mach/mach_init.h>
#   include <mach/semaphore.h>
#   include <mach/task.h>
    typedef semaphore_t cilk_semaphore_t;
#elif defined _WIN32
#   include "windows-clean.h"
    typedef HANDLE cilk_semaphore_t;
#else // Linux/MIC
#   include <errno.h>
#   include <semaphore.h>
#   include <stdio.h>
    typedef sem_t cilk_semaphore_t;
#endif // Linux/MIC

#include "bug.h"
#include "cilk_malloc.h"
#include "signal_node.h"

/**
 * Interface within the tree to notify workers to wait without consuming cycles
 * to expend cycles trying to steal.
 *
 * cilk_semaphore_t is implemented as an auto-reset event on Windows, and
 * as a semaphore_t on Linux and MacOS.
 */
struct signal_node_t
{
    /** 0 if the worker should wait, 1 if it should be running. */
    volatile unsigned int run;

    /** OS-specific semaphore on which the worker can wait. */
    cilk_semaphore_t sem;
};

/******************************************************************************/
/* Semaphore-abstraction functions                                            */
/******************************************************************************/

/*
 * All of these functions are simple wrappers for the system-specific semaphore
 * functions.  This keeps the rest of the code reasonably clean and readable.
 */

#if defined __APPLE__
static void initialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    kern_return_t kstatus
        = semaphore_create(mach_task_self(), sem, SYNC_POLICY_FIFO, 0);
    assert(kstatus == KERN_SUCCESS);
}
static void deinitialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    kern_return_t kstatus = semaphore_destroy(mach_task_self(), *sem);
    assert(kstatus == KERN_SUCCESS);
}
static void wait_on_cilk_semaphore (cilk_semaphore_t *sem)
{
    kern_return_t kstatus = semaphore_wait(*sem);
    assert(kstatus == KERN_SUCCESS);
}
static void signal_cilk_semaphore (cilk_semaphore_t *sem)
{
    kern_return_t kstatus = semaphore_signal(*sem);
    assert(kstatus == KERN_SUCCESS);
}
#elif defined _WIN32
// Note: Windows only provides counting semaphores, and we don't really
// care about the count. So this is implemented using an auto-reset
// event which will automatically reset after the WaitForSingleObject
// call
static void initialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    // Create an auto-reset event
    *sem = CreateEvent(NULL,    // Security attributes
                       FALSE,   // Manual reset
                       FALSE,   // Initial state (initially reset)
                       NULL);   // Name (anonymous)
    CILK_ASSERT (NULL != *sem);
}

static void deinitialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    BOOL result = CloseHandle(*sem);
    CILK_ASSERT (0 != result);
}

static void wait_on_cilk_semaphore (cilk_semaphore_t *sem)
{
    // WaitForSingleObject will reset the event
    DWORD result = WaitForSingleObject (*sem, INFINITE);
    CILK_ASSERT (WAIT_OBJECT_0 == result);
}
static void signal_cilk_semaphore (cilk_semaphore_t *sem)
{
    BOOL result = SetEvent (*sem);
    CILK_ASSERT (0 != result);
}
#else // Linux/MIC
static void initialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    int status = sem_init(sem, 0, 0);
    assert(0 == status);
}
static void deinitialize_cilk_semaphore (cilk_semaphore_t *sem)
{
    int status = sem_destroy(sem);
    assert(0 == status);
}
static void wait_on_cilk_semaphore (cilk_semaphore_t *sem)
{
    int status;

    do {
        status = sem_wait(sem);
    } while (status != 0 && errno == EINTR);

    if (status != 0) {
        perror("sem_wait");
        abort();
    }
}
static void signal_cilk_semaphore (cilk_semaphore_t *sem)
{
    sem_post(sem);
}
#endif // Linux/MIC

/******************************************************************************/
/* Runtime interface functions                                                */
/******************************************************************************/

/*
 * Return a newly malloc'd and initialized signal_node_t.
 */
COMMON_SYSDEP
signal_node_t *signal_node_create(void)
{
     signal_node_t *node;

    node = ( signal_node_t*)
        __cilkrts_malloc(sizeof( signal_node_t));
    node->run = 0;
    initialize_cilk_semaphore(&node->sem);

    return node;
}

/*
 * Clean and free a signal_node_t.
 */
void signal_node_destroy(signal_node_t *node)
{
    CILK_ASSERT(node);
    deinitialize_cilk_semaphore(&node->sem);
    __cilkrts_free(node);
}

/*
 * Return 1 if the node thinks the worker should go to sleep, 0 otherwise.
 */
unsigned int signal_node_should_wait(signal_node_t *node)
{
    CILK_ASSERT(node);
    return !node->run;
}

/*
 * Send a message to the node that the worker will eventually read.
 */
void signal_node_msg(signal_node_t *node, unsigned int msg)
{
    CILK_ASSERT(node);
    switch (msg) {
    case 0:                    // worker should go to sleep.
        node->run = msg;
        break;
    case 1:                    // worker should be awake.
        node->run = msg;
        signal_cilk_semaphore(&node->sem);
        break;
    default:                   // error.
        CILK_ASSERT(0 == "Bad signal_node_t message.");
    }
}

/*
 * The current worker will wait on the semaphore.
 */
void signal_node_wait(signal_node_t *node)
{
    CILK_ASSERT(node);
    while (signal_node_should_wait(node)) {
        // The loop is here to consume extra semaphore signals that might have
        // accumulated.  No point in passing on the accumulation.
        wait_on_cilk_semaphore(&node->sem);
    }
}