/*

 * work_thread.c - threads implementation for blocking worker child.

 */

#include <config.h>

#include "ntp_workimpl.h"

#ifdef WORK_THREAD

#include <stdio.h>

#include <ctype.h>

#include <signal.h>

#ifndef SYS_WINNT

#include <pthread.h>

#endif

#include "ntp_stdlib.h"

#include "ntp_malloc.h"

#include "ntp_syslog.h"

#include "ntpd.h"

#include "ntp_io.h"

#include "ntp_assert.h"

#include "ntp_unixtime.h"

#include "timespecops.h"

#include "ntp_worker.h"

#define CHILD_EXIT_REQ  ((blocking_pipe_header *)(intptr_t)-1)

#define CHILD_GONE_RESP CHILD_EXIT_REQ

/* Queue size increments:

 * The request queue grows a bit faster than the response queue -- the

 * daemon can push requests and pull results faster on avarage than the

 * worker can process requests and push results...  If this really pays

 * off is debatable.

 */

#define WORKITEMS_ALLOC_INC 16

#define RESPONSES_ALLOC_INC 4

/* Fiddle with min/max stack sizes. 64kB minimum seems to work, so we

 * set the maximum to 256kB. If the minimum goes below the

 * system-defined minimum stack size, we have to adjust accordingly.

 */

#ifndef THREAD_MINSTACKSIZE

# define THREAD_MINSTACKSIZE  (64U * 1024)

#endif

#ifndef __sun

#if defined(PTHREAD_STACK_MIN) && THREAD_MINSTACKSIZE < PTHREAD_STACK_MIN

# undef THREAD_MINSTACKSIZE

# define THREAD_MINSTACKSIZE PTHREAD_STACK_MIN

#endif

#endif

#ifndef THREAD_MAXSTACKSIZE

# define THREAD_MAXSTACKSIZE  (256U * 1024)

#endif

#if THREAD_MAXSTACKSIZE < THREAD_MINSTACKSIZE

# undef  THREAD_MAXSTACKSIZE

# define THREAD_MAXSTACKSIZE THREAD_MINSTACKSIZE

#endif

/* need a good integer to store a pointer... */

#ifndef UINTPTR_T

# if defined(UINTPTR_MAX)

#  define UINTPTR_T uintptr_t

# elif defined(UINT_PTR)

#  define UINTPTR_T UINT_PTR

# else

#  define UINTPTR_T size_t

# endif

#endif

#ifdef SYS_WINNT

# define thread_exit(c) _endthreadex(c)

# define tickle_sem(sh) ReleaseSemaphore((sh->shnd), 1, NULL)

u_int WINAPI  blocking_thread(void *);

static BOOL same_os_sema(const sem_ref obj, void * osobj);

#else

# define thread_exit(c) pthread_exit((void*)(UINTPTR_T)(c))

# define tickle_sem sem_post

void *    blocking_thread(void *);

static  void  block_thread_signals(sigset_t *);

#endif

#ifdef WORK_PIPE

addremove_io_fd_func    addremove_io_fd;

#else

addremove_io_semaphore_func addremove_io_semaphore;

#endif

static  void  start_blocking_thread(blocking_child *);

static  void  start_blocking_thread_internal(blocking_child *);

static  void  prepare_child_sems(blocking_child *);

static  int wait_for_sem(sem_ref, struct timespec *);

static  int ensure_workitems_empty_slot(blocking_child *);

static  int ensure_workresp_empty_slot(blocking_child *);

static  int queue_req_pointer(blocking_child *, blocking_pipe_header *);

static  void  cleanup_after_child(blocking_child *);

static sema_type worker_mmutex;

static sem_ref   worker_memlock;

/* --------------------------------------------------------------------

 * locking the global worker state table (and other global stuff)

 */

void

worker_global_lock(

  int inOrOut)

{

  if (worker_memlock) {

    if (inOrOut)

      wait_for_sem(worker_memlock, NULL);

    else

      tickle_sem(worker_memlock);

  }

}

/* --------------------------------------------------------------------

 * implementation isolation wrapper

 */

void

exit_worker(

  int exitcode

  )

{

  thread_exit(exitcode); /* see #define thread_exit */

}

/* --------------------------------------------------------------------

 * sleep for a given time or until the wakup semaphore is tickled.

 */

int

worker_sleep(

  blocking_child *  c,

  time_t      seconds

  )

{

  struct timespec until;

  int   rc;

# ifdef HAVE_CLOCK_GETTIME

  if (0 != clock_gettime(CLOCK_REALTIME, &until)) {

    msyslog(LOG_ERR, "worker_sleep: clock_gettime() failed: %m");

    return -1;

  }

# else

  if (0 != getclock(TIMEOFDAY, &until)) {

    msyslog(LOG_ERR, "worker_sleep: getclock() failed: %m");

    return -1;

  }

# endif

  until.tv_sec += seconds;

  rc = wait_for_sem(c->wake_scheduled_sleep, &until);

  if (0 == rc)

    return -1;

  if (-1 == rc && ETIMEDOUT == errno)

    return 0;

  msyslog(LOG_ERR, "worker_sleep: sem_timedwait: %m");

  return -1;

}

/* --------------------------------------------------------------------

 * Wake up a worker that takes a nap.

 */

void

interrupt_worker_sleep(void)

{

  u_int     idx;

  blocking_child *  c;

  for (idx = 0; idx < blocking_children_alloc; idx++) {

    c = blocking_children[idx];

    if (NULL == c || NULL == c->wake_scheduled_sleep)

      continue;

    tickle_sem(c->wake_scheduled_sleep);

  }

}

/* --------------------------------------------------------------------

 * Make sure there is an empty slot at the head of the request

 * queue. Tell if the queue is currently empty.

 */

static int

ensure_workitems_empty_slot(

  blocking_child *c

  )

{

  /*

  ** !!! PRECONDITION: caller holds access lock!

  **

  ** This simply tries to increase the size of the buffer if it

  ** becomes full. The resize operation does *not* maintain the

  ** order of requests, but that should be irrelevant since the

  ** processing is considered asynchronous anyway.

  **

  ** Return if the buffer is currently empty.

  */

  static const size_t each =

      sizeof(blocking_children[0]->workitems[0]);

  size_t  new_alloc;

  size_t  slots_used;

  size_t  sidx;

  slots_used = c->head_workitem - c->tail_workitem;

  if (slots_used >= c->workitems_alloc) {

    new_alloc  = c->workitems_alloc + WORKITEMS_ALLOC_INC;

    c->workitems = erealloc(c->workitems, new_alloc * each);

    for (sidx = c->workitems_alloc; sidx < new_alloc; ++sidx)

        c->workitems[sidx] = NULL;

    c->tail_workitem   = 0;

    c->head_workitem   = c->workitems_alloc;

    c->workitems_alloc = new_alloc;

  }

  INSIST(NULL == c->workitems[c->head_workitem % c->workitems_alloc]);

  return (0 == slots_used);

}

/* --------------------------------------------------------------------

 * Make sure there is an empty slot at the head of the response

 * queue. Tell if the queue is currently empty.

 */

static int

ensure_workresp_empty_slot(

  blocking_child *c

  )

{

  /*

  ** !!! PRECONDITION: caller holds access lock!

  **

  ** Works like the companion function above.

  */

  static const size_t each =

      sizeof(blocking_children[0]->responses[0]);

  size_t  new_alloc;

  size_t  slots_used;

  size_t  sidx;

  slots_used = c->head_response - c->tail_response;

  if (slots_used >= c->responses_alloc) {

    new_alloc  = c->responses_alloc + RESPONSES_ALLOC_INC;

    c->responses = erealloc(c->responses, new_alloc * each);

    for (sidx = c->responses_alloc; sidx < new_alloc; ++sidx)

        c->responses[sidx] = NULL;

    c->tail_response   = 0;

    c->head_response   = c->responses_alloc;

    c->responses_alloc = new_alloc;

  }

  INSIST(NULL == c->responses[c->head_response % c->responses_alloc]);

  return (0 == slots_used);

}

/* --------------------------------------------------------------------

 * queue_req_pointer() - append a work item or idle exit request to

 *       blocking_workitems[]. Employ proper locking.

 */

static int

queue_req_pointer(

  blocking_child  * c,

  blocking_pipe_header *  hdr

  )

{

  size_t qhead;

  /* >>>> ACCESS LOCKING STARTS >>>> */

  wait_for_sem(c->accesslock, NULL);

  ensure_workitems_empty_slot(c);

  qhead = c->head_workitem;

  c->workitems[qhead % c->workitems_alloc] = hdr;

  c->head_workitem = 1 + qhead;

  tickle_sem(c->accesslock);

  /* <<<< ACCESS LOCKING ENDS <<<< */

  /* queue consumer wake-up notification */

  tickle_sem(c->workitems_pending);

  return 0;

}

/* --------------------------------------------------------------------

 * API function to make sure a worker is running, a proper private copy

 * of the data is made, the data eneterd into the queue and the worker

 * is signalled.

 */

int

send_blocking_req_internal(

  blocking_child *  c,

  blocking_pipe_header *  hdr,

  void *      data

  )

{

  blocking_pipe_header *  threadcopy;

  size_t      payload_octets;

  REQUIRE(hdr != NULL);

  REQUIRE(data != NULL);

  DEBUG_REQUIRE(BLOCKING_REQ_MAGIC == hdr->magic_sig);

  if (hdr->octets <= sizeof(*hdr))

    return 1; /* failure */

  payload_octets = hdr->octets - sizeof(*hdr);

  if (NULL == c->thread_ref)

    start_blocking_thread(c);

  threadcopy = emalloc(hdr->octets);

  memcpy(threadcopy, hdr, sizeof(*hdr));

  memcpy((char *)threadcopy + sizeof(*hdr), data, payload_octets);

  return queue_req_pointer(c, threadcopy);

}

/* --------------------------------------------------------------------

 * Wait for the 'incoming queue no longer empty' signal, lock the shared

 * structure and dequeue an item.

 */

blocking_pipe_header *

receive_blocking_req_internal(

  blocking_child *  c

  )

{

  blocking_pipe_header *  req;

  size_t      qhead, qtail;

  req = NULL;

  do {

    /* wait for tickle from the producer side */

    wait_for_sem(c->workitems_pending, NULL);

    /* >>>> ACCESS LOCKING STARTS >>>> */

    wait_for_sem(c->accesslock, NULL);

    qhead = c->head_workitem;

    do {

      qtail = c->tail_workitem;

      if (qhead == qtail)

        break;

      c->tail_workitem = qtail + 1;

      qtail %= c->workitems_alloc;

      req = c->workitems[qtail];

      c->workitems[qtail] = NULL;

    } while (NULL == req);

    tickle_sem(c->accesslock);

    /* <<<< ACCESS LOCKING ENDS <<<< */

  } while (NULL == req);

  INSIST(NULL != req);

  if (CHILD_EXIT_REQ == req) { /* idled out */

    send_blocking_resp_internal(c, CHILD_GONE_RESP);

    req = NULL;

  }

  return req;

}

/* --------------------------------------------------------------------

 * Push a response into the return queue and eventually tickle the

 * receiver.

 */

int

send_blocking_resp_internal(

  blocking_child *  c,

  blocking_pipe_header *  resp

  )

{

  size_t  qhead;

  int empty;

  /* >>>> ACCESS LOCKING STARTS >>>> */

  wait_for_sem(c->accesslock, NULL);

  empty = ensure_workresp_empty_slot(c);

  qhead = c->head_response;

  c->responses[qhead % c->responses_alloc] = resp;

  c->head_response = 1 + qhead;

  tickle_sem(c->accesslock);

  /* <<<< ACCESS LOCKING ENDS <<<< */

  /* queue consumer wake-up notification */

  if (empty)

  {

#     ifdef WORK_PIPE

    if (1 != write(c->resp_write_pipe, "", 1))

      msyslog(LOG_WARNING, "async resolver: %s",

        "failed to notify main thread!");

#     else

    tickle_sem(c->responses_pending);

#     endif

  }

  return 0;

}

#ifndef WORK_PIPE

/* --------------------------------------------------------------------

 * Check if a (Windows-)hanndle to a semaphore is actually the same we

 * are using inside the sema wrapper.

 */

static BOOL

same_os_sema(

  const sem_ref obj,

  void*   osh

  )

{

  return obj && osh && (obj->shnd == (HANDLE)osh);

}

/* --------------------------------------------------------------------

 * Find the shared context that associates to an OS handle and make sure

 * the data is dequeued and processed.

 */

void

handle_blocking_resp_sem(

  void *  context

  )

{

  blocking_child *  c;

  u_int     idx;

  c = NULL;

  for (idx = 0; idx < blocking_children_alloc; idx++) {

    c = blocking_children[idx];

    if (c != NULL &&

      c->thread_ref != NULL &&

      same_os_sema(c->responses_pending, context))

      break;

  }

  if (idx < blocking_children_alloc)

    process_blocking_resp(c);

}

#endif  /* !WORK_PIPE */

/* --------------------------------------------------------------------

 * Fetch the next response from the return queue. In case of signalling

 * via pipe, make sure the pipe is flushed, too.

 */

blocking_pipe_header *

receive_blocking_resp_internal(

  blocking_child *  c

  )

{

  blocking_pipe_header *  removed;

  size_t      qhead, qtail, slot;

#ifdef WORK_PIPE

  int     rc;

  char      scratch[32];

  do

    rc = read(c->resp_read_pipe, scratch, sizeof(scratch));

  while (-1 == rc && EINTR == errno);

#endif

  /* >>>> ACCESS LOCKING STARTS >>>> */

  wait_for_sem(c->accesslock, NULL);

  qhead = c->head_response;

  qtail = c->tail_response;

  for (removed = NULL; !removed && (qhead != qtail); ++qtail) {

    slot = qtail % c->responses_alloc;

    removed = c->responses[slot];

    c->responses[slot] = NULL;

  }

  c->tail_response = qtail;

  tickle_sem(c->accesslock);

  /* <<<< ACCESS LOCKING ENDS <<<< */

  if (NULL != removed) {

    DEBUG_ENSURE(CHILD_GONE_RESP == removed ||

           BLOCKING_RESP_MAGIC == removed->magic_sig);

  }

  if (CHILD_GONE_RESP == removed) {

    cleanup_after_child(c);

    removed = NULL;

  }

  return removed;

}

/* --------------------------------------------------------------------

 * Light up a new worker.

 */

static void

start_blocking_thread(

  blocking_child *  c

  )

{

  DEBUG_INSIST(!c->reusable);

  prepare_child_sems(c);

  start_blocking_thread_internal(c);

}

/* --------------------------------------------------------------------

 * Create a worker thread. There are several differences between POSIX

 * and Windows, of course -- most notably the Windows thread is no

 * detached thread, and we keep the handle around until we want to get

 * rid of the thread. The notification scheme also differs: Windows

 * makes use of semaphores in both directions, POSIX uses a pipe for

 * integration with 'select()' or alike.

 */

static void

start_blocking_thread_internal(

  blocking_child *  c

  )

#ifdef SYS_WINNT

{

  BOOL  resumed;

  c->thread_ref = NULL;

  (*addremove_io_semaphore)(c->responses_pending->shnd, FALSE);

  c->thr_table[0].thnd =

    (HANDLE)_beginthreadex(

      NULL,

      0,

      &blocking_thread,

      c,

      CREATE_SUSPENDED,

      NULL);

  if (NULL == c->thr_table[0].thnd) {

    msyslog(LOG_ERR, "start blocking thread failed: %m");

    exit(-1);

  }

  /* remember the thread priority is only within the process class */

  if (!SetThreadPriority(c->thr_table[0].thnd,

             THREAD_PRIORITY_BELOW_NORMAL))

    msyslog(LOG_ERR, "Error lowering blocking thread priority: %m");

  resumed = ResumeThread(c->thr_table[0].thnd);

  DEBUG_INSIST(resumed);

  c->thread_ref = &c->thr_table[0];

}

#else /* pthreads start_blocking_thread_internal() follows */

{

# ifdef NEED_PTHREAD_INIT

  static int  pthread_init_called;

# endif

  pthread_attr_t  thr_attr;

  int   rc;

  int   pipe_ends[2]; /* read then write */

  int   is_pipe;

  int   flags;

  size_t    ostacksize;

  size_t    nstacksize;

  sigset_t  saved_sig_mask;

  c->thread_ref = NULL;

# ifdef NEED_PTHREAD_INIT

  /*

   * from lib/isc/unix/app.c:

   * BSDI 3.1 seg faults in pthread_sigmask() if we don't do this.

   */

  if (!pthread_init_called) {

    pthread_init();

    pthread_init_called = TRUE;

  }

# endif

  rc = pipe_socketpair(&pipe_ends[0], &is_pipe);

  if (0 != rc) {

    msyslog(LOG_ERR, "start_blocking_thread: pipe_socketpair() %m");

    exit(1);

  }

  c->resp_read_pipe = move_fd(pipe_ends[0]);

  c->resp_write_pipe = move_fd(pipe_ends[1]);

  c->ispipe = is_pipe;

  flags = fcntl(c->resp_read_pipe, F_GETFL, 0);

  if (-1 == flags) {

    msyslog(LOG_ERR, "start_blocking_thread: fcntl(F_GETFL) %m");

    exit(1);

  }

  rc = fcntl(c->resp_read_pipe, F_SETFL, O_NONBLOCK | flags);

  if (-1 == rc) {

    msyslog(LOG_ERR,

      "start_blocking_thread: fcntl(F_SETFL, O_NONBLOCK) %m");

    exit(1);

  }

  (*addremove_io_fd)(c->resp_read_pipe, c->ispipe, FALSE);

  pthread_attr_init(&thr_attr);

  pthread_attr_setdetachstate(&thr_attr, PTHREAD_CREATE_DETACHED);

#if defined(HAVE_PTHREAD_ATTR_GETSTACKSIZE) && \

    defined(HAVE_PTHREAD_ATTR_SETSTACKSIZE)

  rc = pthread_attr_getstacksize(&thr_attr, &ostacksize);

  if (0 != rc) {

    msyslog(LOG_ERR,

      "start_blocking_thread: pthread_attr_getstacksize() -> %s",

      strerror(rc));

  } else {

    if (ostacksize < THREAD_MINSTACKSIZE)

      nstacksize = THREAD_MINSTACKSIZE;

    else if (ostacksize > THREAD_MAXSTACKSIZE)

      nstacksize = THREAD_MAXSTACKSIZE;

    else

      nstacksize = ostacksize;

    if (nstacksize != ostacksize)

      rc = pthread_attr_setstacksize(&thr_attr, nstacksize);

    if (0 != rc)

      msyslog(LOG_ERR,

        "start_blocking_thread: pthread_attr_setstacksize(0x%lx -> 0x%lx) -> %s",

        (u_long)ostacksize, (u_long)nstacksize,

        strerror(rc));

  }

#else

  UNUSED_ARG(nstacksize);

  UNUSED_ARG(ostacksize);

#endif

#if defined(PTHREAD_SCOPE_SYSTEM) && defined(NEED_PTHREAD_SCOPE_SYSTEM)

  pthread_attr_setscope(&thr_attr, PTHREAD_SCOPE_SYSTEM);

#endif

  c->thread_ref = emalloc_zero(sizeof(*c->thread_ref));

  block_thread_signals(&saved_sig_mask);

  rc = pthread_create(&c->thr_table[0], &thr_attr,

          &blocking_thread, c);

  pthread_sigmask(SIG_SETMASK, &saved_sig_mask, NULL);

  pthread_attr_destroy(&thr_attr);

  if (0 != rc) {

    msyslog(LOG_ERR, "start_blocking_thread: pthread_create() -> %s",

      strerror(rc));

    exit(1);

  }

  c->thread_ref = &c->thr_table[0];

}

#endif

/* --------------------------------------------------------------------

 * block_thread_signals()

 *

 * Temporarily block signals used by ntpd main thread, so that signal

 * mask inherited by child threads leaves them blocked.  Returns prior

 * active signal mask via pmask, to be restored by the main thread

 * after pthread_create().

 */

#ifndef SYS_WINNT

void

block_thread_signals(

  sigset_t *  pmask

  )

{

  sigset_t  block;

  sigemptyset(&block);

# ifdef HAVE_SIGNALED_IO

#  ifdef SIGIO

  sigaddset(&block, SIGIO);

#  endif

#  ifdef SIGPOLL

  sigaddset(&block, SIGPOLL);

#  endif

# endif /* HAVE_SIGNALED_IO */

  sigaddset(&block, SIGALRM);

  sigaddset(&block, MOREDEBUGSIG);

  sigaddset(&block, LESSDEBUGSIG);

# ifdef SIGDIE1

  sigaddset(&block, SIGDIE1);

# endif

# ifdef SIGDIE2

  sigaddset(&block, SIGDIE2);

# endif

# ifdef SIGDIE3

  sigaddset(&block, SIGDIE3);

# endif

# ifdef SIGDIE4

  sigaddset(&block, SIGDIE4);

# endif

# ifdef SIGBUS

  sigaddset(&block, SIGBUS);

# endif

  sigemptyset(pmask);

  pthread_sigmask(SIG_BLOCK, &block, pmask);

}

#endif  /* !SYS_WINNT */

/* --------------------------------------------------------------------

 * Create & destroy semaphores. This is sufficiently different between

 * POSIX and Windows to warrant wrapper functions and close enough to

 * use the concept of synchronization via semaphore for all platforms.

 */

static sem_ref

create_sema(

  sema_type*  semptr,

  u_int   inival,

  u_int   maxval)

{

#ifdef SYS_WINNT

  long svini, svmax;

  if (NULL != semptr) {

    svini = (inival < LONG_MAX)

        ? (long)inival : LONG_MAX;

    svmax = (maxval < LONG_MAX && maxval > 0)

        ? (long)maxval : LONG_MAX;

    semptr->shnd = CreateSemaphore(NULL, svini, svmax, NULL);

    if (NULL == semptr->shnd)

      semptr = NULL;

  }

#else

  (void)maxval;

  if (semptr && sem_init(semptr, FALSE, inival))

    semptr = NULL;

#endif

  return semptr;

}

/* ------------------------------------------------------------------ */

static sem_ref

delete_sema(

  sem_ref obj)

{

#   ifdef SYS_WINNT

  if (obj) {

    if (obj->shnd)

      CloseHandle(obj->shnd);

    obj->shnd = NULL;

  }

#   else

  if (obj)

    sem_destroy(obj);

#   endif

  return NULL;

}

/* --------------------------------------------------------------------

 * prepare_child_sems()

 *

 * create sync & access semaphores

 *

 * All semaphores are cleared, only the access semaphore has 1 unit.

 * Childs wait on 'workitems_pending', then grabs 'sema_access'

 * and dequeues jobs. When done, 'sema_access' is given one unit back.

 *

 * The producer grabs 'sema_access', manages the queue, restores

 * 'sema_access' and puts one unit into 'workitems_pending'.

 *

 * The story goes the same for the response queue.

 */

static void

prepare_child_sems(

  blocking_child *c

  )

{

  if (NULL == worker_memlock)

    worker_memlock = create_sema(&worker_mmutex, 1, 1);

  c->accesslock           = create_sema(&c->sem_table[0], 1, 1);

  c->workitems_pending    = create_sema(&c->sem_table[1], 0, 0);

  c->wake_scheduled_sleep = create_sema(&c->sem_table[2], 0, 1);

#   ifndef WORK_PIPE

  c->responses_pending    = create_sema(&c->sem_table[3], 0, 0);

#   endif

}

/* --------------------------------------------------------------------

 * wait for semaphore. Where the wait can be interrupted, it will

 * internally resume -- When this function returns, there is either no

 * semaphore at all, a timeout occurred, or the caller could

 * successfully take a token from the semaphore.

 *

 * For untimed wait, not checking the result of this function at all is

 * definitely an option.

 */

static int

wait_for_sem(

  sem_ref     sem,

  struct timespec * timeout   /* wall-clock */

  )

#ifdef SYS_WINNT

{

  struct timespec now;

  struct timespec delta;

  DWORD   msec;

  DWORD   rc;

  if (!(sem && sem->shnd)) {

    errno = EINVAL;

    return -1;

  }

  if (NULL == timeout) {

    msec = INFINITE;

  } else {

    getclock(TIMEOFDAY, &now);

    delta = sub_tspec(*timeout, now);

    if (delta.tv_sec < 0) {

      msec = 0;

    } else if ((delta.tv_sec + 1) >= (MAXDWORD / 1000)) {

      msec = INFINITE;

    } else {

      msec = 1000 * (DWORD)delta.tv_sec;

      msec += delta.tv_nsec / (1000 * 1000);

    }

  }

  rc = WaitForSingleObject(sem->shnd, msec);

  if (WAIT_OBJECT_0 == rc)

    return 0;

  if (WAIT_TIMEOUT == rc) {

    errno = ETIMEDOUT;

    return -1;

  }

  msyslog(LOG_ERR, "WaitForSingleObject unexpected 0x%x", rc);

  errno = EFAULT;

  return -1;

}

#else /* pthreads wait_for_sem() follows */

{

  int rc = -1;

  if (sem) do {

      if (NULL == timeout)

        rc = sem_wait(sem);

      else

        rc = sem_timedwait(sem, timeout);

    } while (rc == -1 && errno == EINTR);

  else

    errno = EINVAL;

  return rc;

}

#endif

/* --------------------------------------------------------------------

 * blocking_thread - thread functions have WINAPI (aka 'stdcall')

 * calling conventions under Windows and POSIX-defined signature

 * otherwise.

 */

#ifdef SYS_WINNT

u_int WINAPI

#else

void *

#endif

blocking_thread(

  void *  ThreadArg

  )

{

  blocking_child *c;

  c = ThreadArg;

  exit_worker(blocking_child_common(c));

  /* NOTREACHED */

  return 0;

}

/* --------------------------------------------------------------------

 * req_child_exit() runs in the parent.

 *

 * This function is called from from the idle timer, too, and possibly

 * without a thread being there any longer. Since we have folded up our

 * tent in that case and all the semaphores are already gone, we simply

 * ignore this request in this case.

 *

 * Since the existence of the semaphores is controlled exclusively by

 * the parent, there's no risk of data race here.

 */

int

req_child_exit(

  blocking_child *c

  )

{

  return (c->accesslock)

      ? queue_req_pointer(c, CHILD_EXIT_REQ)

      : 0;

}

/* --------------------------------------------------------------------

 * cleanup_after_child() runs in parent.

 */

static void

cleanup_after_child(

  blocking_child *  c

  )

{

  DEBUG_INSIST(!c->reusable);

#   ifdef SYS_WINNT

  /* The thread was not created in detached state, so we better

   * clean up.

   */

  if (c->thread_ref && c->thread_ref->thnd) {

    WaitForSingleObject(c->thread_ref->thnd, INFINITE);

    INSIST(CloseHandle(c->thread_ref->thnd));

    c->thread_ref->thnd = NULL;

  }

#   endif

  c->thread_ref = NULL;

  /* remove semaphores and (if signalling vi IO) pipes */

  c->accesslock           = delete_sema(c->accesslock);

  c->workitems_pending    = delete_sema(c->workitems_pending);

  c->wake_scheduled_sleep = delete_sema(c->wake_scheduled_sleep);

#   ifdef WORK_PIPE

  DEBUG_INSIST(-1 != c->resp_read_pipe);

  DEBUG_INSIST(-1 != c->resp_write_pipe);

  (*addremove_io_fd)(c->resp_read_pipe, c->ispipe, TRUE);

  close(c->resp_write_pipe);

  close(c->resp_read_pipe);

  c->resp_write_pipe = -1;

  c->resp_read_pipe = -1;

#   else

  DEBUG_INSIST(NULL != c->responses_pending);

  (*addremove_io_semaphore)(c->responses_pending->shnd, TRUE);

  c->responses_pending = delete_sema(c->responses_pending);

#   endif

  /* Is it necessary to check if there are pending requests and

   * responses? If so, and if there are, what to do with them?

   */

  /* re-init buffer index sequencers */

  c->head_workitem = 0;

  c->tail_workitem = 0;

  c->head_response = 0;

  c->tail_response = 0;

  c->reusable = TRUE;

}

#else /* !WORK_THREAD follows */

char work_thread_nonempty_compilation_unit;

#endif