/* 
   Unix SMB/Netbios implementation.
   Version 3.0
   Samba database functions
   Copyright (C) Anton Blanchard                   2001
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#if HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <time.h>
#include <panda/panda_tdb.h>
#include <panda/panda_spinlock.h>

#define DEBUG

#ifdef USE_SPINLOCKS

/*
 * ARCH SPECIFIC
 */

#if defined(SPARC_SPINLOCKS)

static inline int
__spin_trylock (spinlock_t * lock)
{
  unsigned int result;

  asm volatile ("ldstub    [%1], %0":"=r" (result):"r" (lock):"memory");

  return (result == 0) ? 0 : EBUSY;
}

static inline void
__spin_unlock (spinlock_t * lock)
{
  asm volatile ("":::"memory");
  *lock = 0;
}

static inline void
__spin_lock_init (spinlock_t * lock)
{
  *lock = 0;
}

static inline int
__spin_is_locked (spinlock_t * lock)
{
  return (*lock != 0);
}

#elif defined(POWERPC_SPINLOCKS)

static inline int
__spin_trylock (spinlock_t * lock)
{
  unsigned int result;

  __asm__ __volatile__ ("1:	lwarx		%0,0,%1\n\
	cmpwi		0,%0,0\n\
	li		%0,0\n\
	bne-		2f\n\
	li		%0,1\n\
	stwcx.		%0,0,%1\n\
	bne-		1b\n\
	isync\n\
2:":"=&r" (result):"r" (lock):"cr0", "memory");

  return (result == 1) ? 0 : EBUSY;
}

static inline void
__spin_unlock (spinlock_t * lock)
{
  asm volatile ("eieio":::"memory");
  *lock = 0;
}

static inline void
__spin_lock_init (spinlock_t * lock)
{
  *lock = 0;
}

static inline int
__spin_is_locked (spinlock_t * lock)
{
  return (*lock != 0);
}

#elif defined(INTEL_SPINLOCKS)

static inline int
__spin_trylock (spinlock_t * lock)
{
  int oldval;

  asm volatile ("xchgl %0,%1":"=r" (oldval), "=m" (*lock):"0" (0):"memory");

  return oldval > 0 ? 0 : EBUSY;
}

static inline void
__spin_unlock (spinlock_t * lock)
{
  asm volatile ("":::"memory");
  *lock = 1;
}

static inline void
__spin_lock_init (spinlock_t * lock)
{
  *lock = 1;
}

static inline int
__spin_is_locked (spinlock_t * lock)
{
  return (*lock != 1);
}

#elif defined(MIPS_SPINLOCKS)

static inline unsigned int
load_linked (unsigned long addr)
{
  unsigned int res;

  __asm__ __volatile__ ("ll\t%0,(%1)":"=r" (res):"r" (addr));

  return res;
}

static inline unsigned int
store_conditional (unsigned long addr, unsigned int value)
{
  unsigned int res;

  __asm__ __volatile__ ("sc\t%0,(%2)":"=r" (res):"0" (value), "r" (addr));
  return res;
}

static inline int
__spin_trylock (spinlock_t * lock)
{
  unsigned int mw;

  do
    {
      mw = load_linked (lock);
      if (mw)
	return EBUSY;
    }
  while (!store_conditional (lock, 1));

  asm volatile ("":::"memory");

  return 0;
}

static inline void
__spin_unlock (spinlock_t * lock)
{
  asm volatile ("":::"memory");
  *lock = 0;
}

static inline void
__spin_lock_init (spinlock_t * lock)
{
  *lock = 0;
}

static inline int
__spin_is_locked (spinlock_t * lock)
{
  return (*lock != 0);
}

#else
#error Need to implement spinlock code in spinlock.c
#endif

/*
 * OS SPECIFIC
 */

static void
yield_cpu (void)
{
  struct timespec tm;

#ifdef USE_SCHED_YIELD
  sched_yield ();
#else
  /* Linux will busy loop for delays < 2ms on real time tasks */
  tm.tv_sec = 0;
  tm.tv_nsec = 2000000L + 1;
  nanosleep (&tm, NULL);
#endif
}

static int
this_is_smp (void)
{
  return 0;
}

/*
 * GENERIC
 */

static int smp_machine = 0;

static inline void
__spin_lock (spinlock_t * lock)
{
  int ntries = 0;

  while (__spin_trylock (lock))
    {
      while (__spin_is_locked (lock))
	{
	  if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
	    continue;
	  yield_cpu ();
	}
    }
}

static void
__read_lock (tdb_rwlock_t * rwlock)
{
  int ntries = 0;

  while (1)
    {
      __spin_lock (&rwlock->lock);

      if (!(rwlock->count & RWLOCK_BIAS))
	{
	  rwlock->count++;
	  __spin_unlock (&rwlock->lock);
	  return;
	}

      __spin_unlock (&rwlock->lock);

      while (rwlock->count & RWLOCK_BIAS)
	{
	  if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
	    continue;
	  yield_cpu ();
	}
    }
}

static void
__write_lock (tdb_rwlock_t * rwlock)
{
  int ntries = 0;

  while (1)
    {
      __spin_lock (&rwlock->lock);

      if (rwlock->count == 0)
	{
	  rwlock->count |= RWLOCK_BIAS;
	  __spin_unlock (&rwlock->lock);
	  return;
	}

      __spin_unlock (&rwlock->lock);

      while (rwlock->count != 0)
	{
	  if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
	    continue;
	  yield_cpu ();
	}
    }
}

static void
__write_unlock (tdb_rwlock_t * rwlock)
{
  __spin_lock (&rwlock->lock);

#ifdef DEBUG
  if (!(rwlock->count & RWLOCK_BIAS))
    fprintf (stderr, "bug: write_unlock\n");
#endif

  rwlock->count &= ~RWLOCK_BIAS;
  __spin_unlock (&rwlock->lock);
}

static void
__read_unlock (tdb_rwlock_t * rwlock)
{
  __spin_lock (&rwlock->lock);

#ifdef DEBUG
  if (!rwlock->count)
    fprintf (stderr, "bug: read_unlock\n");

  if (rwlock->count & RWLOCK_BIAS)
    fprintf (stderr, "bug: read_unlock\n");
#endif

  rwlock->count--;
  __spin_unlock (&rwlock->lock);
}

/* TDB SPECIFIC */

/* lock a list in the database. list -1 is the alloc list */
int
tdb_spinlock (TDB_CONTEXT * tdb, int list, int rw_type)
{
  tdb_rwlock_t *rwlocks;

  if (!tdb->map_ptr)
    return -1;
  rwlocks = (tdb_rwlock_t *) ((char *) tdb->map_ptr + tdb->header.rwlocks);

  switch (rw_type)
    {
    case F_RDLCK:
      __read_lock (&rwlocks[list + 1]);
      break;

    case F_WRLCK:
      __write_lock (&rwlocks[list + 1]);
      break;

    default:
      return TDB_ERRCODE (TDB_ERR_LOCK, -1);
    }
  return 0;
}

/* unlock the database. */
int
tdb_spinunlock (TDB_CONTEXT * tdb, int list, int rw_type)
{
  tdb_rwlock_t *rwlocks;

  if (!tdb->map_ptr)
    return -1;
  rwlocks = (tdb_rwlock_t *) ((char *) tdb->map_ptr + tdb->header.rwlocks);

  switch (rw_type)
    {
    case F_RDLCK:
      __read_unlock (&rwlocks[list + 1]);
      break;

    case F_WRLCK:
      __write_unlock (&rwlocks[list + 1]);
      break;

    default:
      return TDB_ERRCODE (TDB_ERR_LOCK, -1);
    }

  return 0;
}

int
tdb_create_rwlocks (int fd, unsigned int hash_size)
{
  unsigned size, i;
  tdb_rwlock_t *rwlocks;

  size = (hash_size + 1) * sizeof (tdb_rwlock_t);
  rwlocks = malloc (size);
  if (!rwlocks)
    return -1;

  for (i = 0; i < hash_size + 1; i++)
    {
      __spin_lock_init (&rwlocks[i].lock);
      rwlocks[i].count = 0;
    }

  /* Write it out (appending to end) */
  if (write (fd, rwlocks, size) != size)
    {
      free (rwlocks);
      return -1;
    }
  smp_machine = this_is_smp ();
  free (rwlocks);
  return 0;
}

int
tdb_clear_spinlocks (TDB_CONTEXT * tdb)
{
  tdb_rwlock_t *rwlocks;
  unsigned i;

  if (tdb->header.rwlocks == 0)
    return 0;
  if (!tdb->map_ptr)
    return -1;

  /* We're mmapped here */
  rwlocks = (tdb_rwlock_t *) ((char *) tdb->map_ptr + tdb->header.rwlocks);
  for (i = 0; i < tdb->header.hash_size + 1; i++)
    {
      __spin_lock_init (&rwlocks[i].lock);
      rwlocks[i].count = 0;
    }
  return 0;
}
#else
int
tdb_create_rwlocks (int fd, unsigned int hash_size)
{
  return 0;
}

int
tdb_spinlock (TDB_CONTEXT * tdb, int list, int rw_type)
{
  return -1;
}

int
tdb_spinunlock (TDB_CONTEXT * tdb, int list, int rw_type)
{
  return -1;
}

/* Non-spinlock version: remove spinlock pointer */
int
tdb_clear_spinlocks (TDB_CONTEXT * tdb)
{
  tdb_off off = (tdb_off) ((char *) &tdb->header.rwlocks
			   - (char *) &tdb->header);

  tdb->header.rwlocks = 0;
  if (lseek (tdb->fd, off, SEEK_SET) != off
      || write (tdb->fd, (void *) &tdb->header.rwlocks,
		sizeof (tdb->header.rwlocks)) != sizeof (tdb->header.rwlocks))
    return -1;
  return 0;
}
#endif