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/** @file include/ut0mutex.ic
 Mutex implementation include file

 Created 2012/08/21 Sunny Bains
 *******************************************************/

#include "sync0arr.h"
#include "sync0debug.h"

/**
Wait in the sync array.
@return true if the mutex acquisition was successful. */

template <template <typename> class Policy>
bool TTASEventMutex<Policy>::wait(const char *filename, uint32_t line,
                                  uint32_t spin) UNIV_NOTHROW {
  sync_cell_t *cell;
  sync_array_t *sync_arr;

  sync_arr = sync_array_get_and_reserve_cell(
      this,
      (m_policy.get_id() == LATCH_ID_BUF_BLOCK_MUTEX ||
       m_policy.get_id() == LATCH_ID_BUF_POOL_ZIP)
          ? SYNC_BUF_BLOCK
          : SYNC_MUTEX,
      filename, line, &cell);

  /* The memory order of the array reservation and
  the change in the waiters field is important: when
  we suspend a thread, we first reserve the cell and
  then set waiters field to 1. When threads are released
  in mutex_exit, the waiters field is first set to zero
  and then the event is set to the signaled state. */

  set_waiters();

  /* Try to reserve still a few times. */

  for (uint32_t i = 0; i < spin; ++i) {
    if (try_lock()) {
      sync_array_free_cell(sync_arr, cell);

      /* Note that in this case we leave
      the waiters field set to 1. We cannot
      reset it to zero, as we do not know if
      there are other waiters. */

      return (true);
    }
  }

  /* Now we know that there has been some thread
  holding the mutex after the change in the wait
  array and the waiters field was made.  Now there
  is no risk of infinite wait on the event. */

  sync_array_wait_event(sync_arr, cell);

  return (false);
}

/** Wakeup any waiting thread(s). */

template <template <typename> class Policy>
void TTASEventMutex<Policy>::signal() UNIV_NOTHROW {
  clear_waiters();

  /* The memory order of resetting the waiters field and
  signaling the object is important. See LEMMA 1 above. */
  os_event_set(m_event);

  sync_array_object_signalled();
}