/****************************************************************************
 * sched/wqueue/work_lpthread.c
 *
 *   Copyright (C) 2009-2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 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.
 * 3. Neither the name NuttX nor the names of its 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
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <unistd.h>
#include <sched.h>
#include <string.h>
#include <errno.h>
#include <queue.h>
#include <debug.h>

#include <nuttx/wqueue.h>
#include <nuttx/kthread.h>
#include <nuttx/kmalloc.h>
#include <nuttx/clock.h>

#include "wqueue/wqueue.h"

#ifdef CONFIG_SCHED_LPWORK

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* The state of the kernel mode, low priority work queue(s). */

struct lp_wqueue_s g_lpwork;

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: work_lpthread
 *
 * Description:
 *   These are the worker thread(s) that performs the actions placed on the
 *   low priority work queue.
 *
 *   These, along with the higher priority worker thread are the kernel mode
 *   work queues (also build in the flat build).  One of these threads also
 *   performs periodic garbage collection (that would otherwise be performed
 *   by the idle thread if CONFIG_SCHED_WORKQUEUE is not defined).  That will
 *   be the lower priority worker thread if it is available.
 *
 *   All kernel mode worker threads are started by the OS during normal
 *   bring up.  This entry point is referenced by OS internally and should
 *   not be accessed by application logic.
 *
 * Input parameters:
 *   argc, argv (not used)
 *
 * Returned Value:
 *   Does not return
 *
 ****************************************************************************/

static int work_lpthread(int argc, char *argv[])
{
#if CONFIG_SCHED_LPNTHREADS > 0
  int wndx;
  pid_t me = getpid();
  int i;

  /* Find out thread index by search the workers in g_lpwork */

  for (wndx = 0, i = 0; i < CONFIG_SCHED_LPNTHREADS; i++)
    {
      if (g_lpwork.worker[i].pid == me)
        {
          wndx = i;
          break;
        }
    }

  DEBUGASSERT(i < CONFIG_SCHED_LPNTHREADS);
#endif

  /* Loop forever */

  for (; ; )
    {
#if CONFIG_SCHED_LPNTHREADS > 0
      /* Thread 0 is special.  Only thread 0 performs period garbage collection */

      if (wndx > 0)
        {
          /* The other threads will perform work, waiting indefinitely until
           * signalled for the next work availability.
           *
           * The special value of zero for the poll period instructs work_process
           * to wait indefinitely until a signal is received.
           */

          work_process((FAR struct kwork_wqueue_s *)&g_lpwork, 0, wndx);
        }
      else
#endif
        {
          /* Perform garbage collection.  This cleans-up memory de-allocations
           * that were queued because they could not be freed in that execution
           * context (for example, if the memory was freed from an interrupt handler).
           * NOTE: If the work thread is disabled, this clean-up is performed by
           * the IDLE thread (at a very, very low priority).
           *
           * In the event of multiple low priority threads, on index == 0 will do
           * the garbage collection.
           */

          sched_garbage_collection();

          /* Then process queued work.  work_process will not return until:
           * (1) there is no further work in the work queue, and (2) the polling
           * period provided by g_lpwork.delay expires.
           */

          work_process((FAR struct kwork_wqueue_s *)&g_lpwork, g_lpwork.delay, 0);
        }
    }

  return OK; /* To keep some compilers happy */
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: work_lpstart
 *
 * Description:
 *   Start the low-priority, kernel-mode worker thread(s)
 *
 * Input parameters:
 *   None
 *
 * Returned Value:
 *   The task ID of the worker thread is returned on success.  A negated
 *   errno value is returned on failure.
 *
 ****************************************************************************/

int work_lpstart(void)
{
  pid_t pid;
  int wndx;

  /* Initialize work queue data structures */

  memset(&g_lpwork, 0, sizeof(struct kwork_wqueue_s));

  g_lpwork.delay = CONFIG_SCHED_LPWORKPERIOD / USEC_PER_TICK;
  dq_init(&g_lpwork.q);

  /* Don't permit any of the threads to run until we have fully initialized
   * g_lpwork.
   */

  sched_lock();

  /* Start the low-priority, kernel mode worker thread(s) */

  sinfo("Starting low-priority kernel worker thread(s)\n");

  for (wndx = 0; wndx < CONFIG_SCHED_LPNTHREADS; wndx++)
    {
       pid = kernel_thread(LPWORKNAME, CONFIG_SCHED_LPWORKPRIORITY,
                           CONFIG_SCHED_LPWORKSTACKSIZE,
                           (main_t)work_lpthread,
                           (FAR char * const *)NULL);

      DEBUGASSERT(pid > 0);
      if (pid < 0)
        {
          int errcode = errno;
          DEBUGASSERT(errcode > 0);

          sllerr("ERROR: kernel_thread %d failed: %d\n", wndx, errcode);
          sched_unlock();
          return -errcode;
        }

      g_lpwork.worker[wndx].pid  = pid;
      g_lpwork.worker[wndx].busy = true;
    }

  sched_unlock();
  return g_lpwork.worker[0].pid;
}

#endif /* CONFIG_SCHED_LPWORK */