#ifndef __monitor_cc
#define __monitor_cc

/* Monitors for the Cray T3E */

#include "ti_config.h"
#include "backend.h"
#include "monitor.h"
#include "ti-gc.h"
#include "eregs.h"

#include <mpp/shmem.h>
#include <mpp/mpphw_t3e.h>
#include <stdio.h>
#include <stdlib.h>



void monitor_destroy(titanium_monitor_t *m)
{
}

#define BACKOFF_THRESHOLD 10
#define BACKOFF_WAIT_RAND 100
#define BACKOFF_WAIT_BASE 10
#define BACKOFF_WAIT_SHIFT 5

void monitor_enter(titanium_monitor_t *m, int proc)
{
  long lock_held;

  /* Flush the Eregs so shmem calls can be made safely */
  er_global_memory_sync();

  /* Get the lock status and grab it if possible. */
  lock_held = shmem_long_cswap(&m->lock_owner, NO_LOCK_OWNER, MYPROC, proc);
  /* Check if lock was not held by this process. */
  if (lock_held != MYPROC) {
    int backoff;

    /* Wait on the lock if it was owned by another process. */
    for (backoff = 0;
	 (backoff < BACKOFF_THRESHOLD) && (lock_held != NO_LOCK_OWNER);
	 backoff++) {
      /* If the lock was not free, poll the lock. */
      lock_held = shmem_long_cswap(&m->lock_owner, NO_LOCK_OWNER, MYPROC,
				   proc);
    }

    /* Back off */
    while (lock_held != NO_LOCK_OWNER) {
      static void spin_loop(int);

      /* Spin for a time. */
      spin_loop((BACKOFF_WAIT_BASE + rand() % BACKOFF_WAIT_RAND) <<
		BACKOFF_WAIT_SHIFT);

      /* If the lock was not free, poll the lock. */
      lock_held = shmem_long_cswap(&m->lock_owner, NO_LOCK_OWNER, MYPROC,
				   proc);
    }
  }
  /* assert(shmem_long_cswap(&m->lock_owner,MYPROC,MYPROC,proc) == MYPROC); */

  /* Increment nesting */
  shmem_short_finc(&m->nesting, proc);

  /* Flush the Eregs */
  er_global_memory_sync();
}

void monitor_exit(titanium_monitor_t *m, int proc)
{
  long lock_held;

  /* Flush the Eregs so shmem calls can be made safely */
  er_global_memory_sync();

  /* Get the lock status. */
  lock_held = shmem_long_cswap(&m->lock_owner, MYPROC, MYPROC, proc);
  /* Check if the lock was owned by this process */
  if (lock_held == MYPROC) {
    long nesting;

    /* Decrement the nesting level */
    nesting = shmem_short_fadd(&m->nesting, -1, proc);

    if (nesting == 1) {
      /* If at the lowest nesting, free the lock. */
      shmem_long_swap(&m->lock_owner, NO_LOCK_OWNER, proc);
    }
  } else {
    /* No-op for now. */
    /* Error: Tried to exit a monitor that was not owned. */
  }

  /* Flush the Eregs */
  er_global_memory_sync();
}


void monitor_wait(jGPointer monitor, ti_time_t *tm) {
  fprintf(stderr, "monitor_wait() is not implemented on the cray-t3e backend\n");
  abort();
  }
void monitor_notify(jGPointer monitor) {
  fprintf(stderr, "monitor_notify() is not implemented on the cray-t3e backend\n");
  abort();
  }
void monitor_notify_all(jGPointer monitor) {
  fprintf(stderr, "monitor_notify_all() is not implemented on the cray-t3e backend\n");
  abort();
  }

/* Turn of the optimizer for the spin code. */
#pragma _CRI noopt
static void spin_loop(int wait_length)
{
  int wait_index;

  /* Spin for a while. */
  for (wait_index = 0; wait_index < wait_length; wait_index++);
}
#pragma _CRI opt

#endif /* __monitor_cc */