/****************************************************************************
 * sched/wqueue/kwork_cancel.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

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

#include <nuttx/config.h>

#include <assert.h>
#include <errno.h>

#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include <nuttx/list.h>
#include <nuttx/sched.h>
#include <nuttx/wqueue.h>

#include "wqueue/wqueue.h"

#ifdef CONFIG_SCHED_WORKQUEUE

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

static int work_qcancel(FAR struct kwork_wqueue_s *wqueue, bool sync,
                        FAR struct work_s *work)
{
  irqstate_t flags;
  pid_t self = sync ? nxsched_gettid() : INVALID_PROCESS_ID;
  int ret = -ENOENT;

  if (wqueue == NULL || work == NULL)
    {
      return -EINVAL;
    }

  /* A work structure becomes available for requeue after it is dequeued,
   * before its callback returns.  Multiple workers can therefore execute
   * callbacks using the same work structure.  Find one such worker and
   * repeat after it finishes until no callback remains.  Exclude the
   * calling worker to avoid self-deadlock.
   */

  for (; ; )
    {
      FAR struct kworker_s *worker = wq_get_worker(wqueue);
      FAR sem_t *sync_wait = NULL;
      int wndx;

      /* Cancelling the work is simply a matter of removing the work
       * structure from the work queue.  This must be done with interrupts
       * disabled because new work is typically added from interrupt
       * handlers.
       */

      flags = spin_lock_irqsave(&wqueue->lock);

      if (!work_available(work))
        {
          /* If the head of the pending queue has changed, reset the timer. */

          if (work_remove(wqueue, work))
            {
              work_timer_reset(wqueue);
            }

          ret = OK;
        }

      /* Otherwise the work is not queued: either it was never queued or a
       * worker has already dequeued it and may be executing its callback
       * right now.  Only the scan below can tell.  Report -ENOENT if the
       * work is neither queued nor running, so that callers (e.g.
       * aio_cancel()) do not free resources that the callback is still
       * using.
       */

      if (sync)
        {
          for (wndx = 0; wndx < wqueue->nthreads; wndx++)
            {
              if (worker[wndx].work == work && worker[wndx].pid != self)
                {
                  worker[wndx].wait_count++;
                  sync_wait = &worker[wndx].wait;
                  ret = OK;
                  break;
                }
            }
        }

      spin_unlock_irqrestore(&wqueue->lock, flags);

      if (sync_wait == NULL)
        {
          return ret;
        }

      nxsem_wait_uninterruptible(sync_wait);
    }
}

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

/****************************************************************************
 * Name: work_cancel/work_cancel_wq
 *
 * Description:
 *   Cancel previously queued work.  This removes work from the work queue.
 *   After work has been cancelled, it may be requeued by calling
 *   work_queue() again.
 *
 * Input Parameters:
 *   qid    - The work queue ID (must be HPWORK or LPWORK)
 *   wqueue - The work queue handle
 *   work   - The previously queued work structure to cancel
 *
 * Returned Value:
 *   Zero on success, a negated errno on failure
 *
 *   -EINVAL - An invalid work queue was specified
 *   -ENOENT - The work is not queued (and, for the sync variant, not
 *             running either)
 *
 ****************************************************************************/

int work_cancel(int qid, FAR struct work_s *work)
{
  return work_qcancel(work_qid2wq(qid), false, work);
}

int work_cancel_wq(FAR struct kwork_wqueue_s *wqueue,
                   FAR struct work_s *work)
{
  return work_qcancel(wqueue, false, work);
}

/****************************************************************************
 * Name: work_cancel_sync/work_cancel_sync_wq
 *
 * Description:
 *   Synchronously cancel previously queued work.  This removes work from
 *   the work queue and waits for callbacks that are already running.  After
 *   work has been cancelled, it may be requeued by calling work_queue()
 *   again.
 *
 * Input Parameters:
 *   qid    - The work queue ID (must be HPWORK or LPWORK)
 *   wqueue - The work queue handle
 *   work   - The previously queued work structure to cancel
 *
 * Returned Value:
 *   Zero means the work was successfully cancelled.
 *   A negated errno value is returned on any failure:
 *
 *   -EINVAL - An invalid work queue was specified
 *
 ****************************************************************************/

int work_cancel_sync(int qid, FAR struct work_s *work)
{
  return work_qcancel(work_qid2wq(qid), true, work);
}

int work_cancel_sync_wq(FAR struct kwork_wqueue_s *wqueue,
                        FAR struct work_s *work)
{
  return work_qcancel(wqueue, true, work);
}

#endif /* CONFIG_SCHED_WORKQUEUE */