/* Copyright (C) 2003-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

#ifndef _LOWLEVELLOCK_H
#define _LOWLEVELLOCK_H	1

#include <time.h>
#include <sys/param.h>
#include <bits/pthreadtypes.h>
#include <atomic.h>
#include <sysdep.h>
#include <kernel-features.h>

#define FUTEX_WAIT		0
#define FUTEX_WAKE		1
#define FUTEX_REQUEUE		3
#define FUTEX_CMP_REQUEUE	4
#define FUTEX_WAKE_OP		5
#define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE	((4 << 24) | 1)
#define FUTEX_LOCK_PI		6
#define FUTEX_UNLOCK_PI		7
#define FUTEX_TRYLOCK_PI	8
#define FUTEX_WAIT_BITSET	9
#define FUTEX_WAKE_BITSET	10
#define FUTEX_WAIT_REQUEUE_PI   11
#define FUTEX_CMP_REQUEUE_PI    12
#define FUTEX_PRIVATE_FLAG	128
#define FUTEX_CLOCK_REALTIME	256

#define FUTEX_BITSET_MATCH_ANY	0xffffffff

/* Values for 'private' parameter of locking macros.  Yes, the
   definition seems to be backwards.  But it is not.  The bit will be
   reversed before passing to the system call.  */
#define LLL_PRIVATE	0
#define LLL_SHARED	FUTEX_PRIVATE_FLAG


#if !defined NOT_IN_libc || defined IS_IN_rtld
/* In libc.so or ld.so all futexes are private.  */
# ifdef __ASSUME_PRIVATE_FUTEX
#  define __lll_private_flag(fl, private) \
  ((fl) | FUTEX_PRIVATE_FLAG)
# else
#  define __lll_private_flag(fl, private) \
  ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex))
# endif
#else
# ifdef __ASSUME_PRIVATE_FUTEX
#  define __lll_private_flag(fl, private) \
  (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
# else
#  define __lll_private_flag(fl, private) \
  (__builtin_constant_p (private)					      \
   ? ((private) == 0							      \
      ? ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex))	      \
      : (fl))								      \
   : ((fl) | (((private) ^ FUTEX_PRIVATE_FLAG)				      \
	      & THREAD_GETMEM (THREAD_SELF, header.private_futex))))
# endif
#endif


#define lll_futex_wait(futexp, val, private) \
  lll_futex_timed_wait(futexp, val, NULL, private)

#define lll_futex_timed_wait(futexp, val, timespec, private) \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
    __ret = INTERNAL_SYSCALL (futex, __err, 4, (long) (futexp),		      \
			      __lll_private_flag (FUTEX_WAIT, private),	      \
			      (val), (timespec));			      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret;		      \
  })

#define lll_futex_timed_wait_bitset(futexp, val, timespec, clockbit, private) \
  ({									\
    INTERNAL_SYSCALL_DECL (__err);					\
    long int __ret;							\
    int __op = FUTEX_WAIT_BITSET | clockbit;				\
    __ret = INTERNAL_SYSCALL (futex, __err, 6, (long) (futexp),		\
			      __lll_private_flag (__op, private),	\
			      (val), (timespec), NULL /* Unused.  */,	\
			      FUTEX_BITSET_MATCH_ANY);			\
    INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret;		\
  })

#define lll_futex_wake(futexp, nr, private) \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
    __ret = INTERNAL_SYSCALL (futex, __err, 4, (long) (futexp),		      \
			      __lll_private_flag (FUTEX_WAKE, private),	      \
			      (nr), 0);	      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret;		      \
  })

#define lll_robust_dead(futexv, private) \
  do									      \
    {									      \
      int *__futexp = &(futexv);					      \
      atomic_or (__futexp, FUTEX_OWNER_DIED);				      \
      lll_futex_wake (__futexp, 1, private);				      \
    }									      \
  while (0)

/* Returns non-zero if error happened, zero if success.  */
#define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
    __ret = INTERNAL_SYSCALL (futex, __err, 6, (long) (futexp),		      \
			      __lll_private_flag (FUTEX_CMP_REQUEUE, private),\
			      (nr_wake), (nr_move), (mutex), (val));	      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err);				      \
  })

/* Returns non-zero if error happened, zero if success.  */
#define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
									      \
    __ret = INTERNAL_SYSCALL (futex, __err, 6, (futexp),		      \
			      __lll_private_flag (FUTEX_WAKE_OP, private),    \
			      (nr_wake), (nr_wake2), (futexp2),		      \
			      FUTEX_OP_CLEAR_WAKE_IF_GT_ONE);		      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err);				      \
  })

/* Priority Inheritance support.  */
#define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
  lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)

#define lll_futex_timed_wait_requeue_pi(futexp, val, timespec, clockbit,      \
					mutex, private)			      \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
    int __op = FUTEX_WAIT_REQUEUE_PI | clockbit;			      \
									      \
    __ret = INTERNAL_SYSCALL (futex, __err, 5, (futexp),		      \
			      __lll_private_flag (__op, private),	      \
			      (val), (timespec), mutex); 		      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret;		      \
  })

#define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, val, priv)  \
  ({									      \
    INTERNAL_SYSCALL_DECL (__err);					      \
    long int __ret;							      \
									      \
    __ret = INTERNAL_SYSCALL (futex, __err, 6, (futexp),		      \
			      __lll_private_flag (FUTEX_CMP_REQUEUE_PI, priv),\
			      (nr_wake), (nr_move), (mutex), (val));	      \
    INTERNAL_SYSCALL_ERROR_P (__ret, __err);				      \
  })

static inline int __attribute__((always_inline))
__lll_trylock(int *futex)
{
  return atomic_compare_and_exchange_val_acq (futex, 1, 0) != 0;
}
#define lll_trylock(lock)	__lll_trylock (&(lock))


static inline int __attribute__((always_inline))
__lll_cond_trylock(int *futex)
{
  return atomic_compare_and_exchange_val_acq (futex, 2, 0) != 0;
}
#define lll_cond_trylock(lock)	__lll_cond_trylock (&(lock))


static inline int __attribute__((always_inline))
__lll_robust_trylock(int *futex, int id)
{
  return atomic_compare_and_exchange_val_acq (futex, id, 0) != 0;
}
#define lll_robust_trylock(lock, id) \
  __lll_robust_trylock (&(lock), id)

extern void __lll_lock_wait_private (int *futex) attribute_hidden;
extern void __lll_lock_wait (int *futex, int private) attribute_hidden;
extern int __lll_robust_lock_wait (int *futex, int private) attribute_hidden;

#define __lll_lock(futex, private)					      \
  ((void) ({								      \
    int *__futex = (futex);						      \
    if (__builtin_expect (atomic_compare_and_exchange_bool_acq (__futex,      \
								1, 0), 0))    \
      {									      \
	if (__builtin_constant_p (private) && (private) == LLL_PRIVATE)	      \
	  __lll_lock_wait_private (__futex);				      \
	else								      \
	  __lll_lock_wait (__futex, private);				      \
      }									      \
  }))
#define lll_lock(futex, private) __lll_lock (&(futex), private)


#define __lll_robust_lock(futex, id, private)				      \
  ({									      \
    int *__futex = (futex);						      \
    int __val = 0;							      \
									      \
    if (__builtin_expect (atomic_compare_and_exchange_bool_acq (__futex, id,  \
								0), 0))	      \
      __val = __lll_robust_lock_wait (__futex, private);		      \
    __val;								      \
  })
#define lll_robust_lock(futex, id, private) \
  __lll_robust_lock (&(futex), id, private)


static inline void __attribute__ ((always_inline))
__lll_cond_lock (int *futex, int private)
{
  if (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0)
    __lll_lock_wait (futex, private);
}
#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)


#define lll_robust_cond_lock(futex, id, private) \
  __lll_robust_lock (&(futex), (id) | FUTEX_WAITERS, private)


extern int __lll_timedlock_wait (int *futex, const struct timespec *,
				 int private) attribute_hidden;
extern int __lll_robust_timedlock_wait (int *futex, const struct timespec *,
					int private) attribute_hidden;

static inline int __attribute__ ((always_inline))
__lll_timedlock (int *futex, const struct timespec *abstime, int private)
{
  int result = 0;
  if (atomic_compare_and_exchange_bool_acq (futex, 1, 0) != 0)
    result = __lll_timedlock_wait (futex, abstime, private);
  return result;
}
#define lll_timedlock(futex, abstime, private) \
  __lll_timedlock (&(futex), abstime, private)


static inline int __attribute__ ((always_inline))
__lll_robust_timedlock (int *futex, const struct timespec *abstime,
			int id, int private)
{
  int result = 0;
  if (atomic_compare_and_exchange_bool_acq (futex, id, 0) != 0)
    result = __lll_robust_timedlock_wait (futex, abstime, private);
  return result;
}
#define lll_robust_timedlock(futex, abstime, id, private) \
  __lll_robust_timedlock (&(futex), abstime, id, private)


#define __lll_unlock(futex, private)					      \
  ((void) ({								      \
    int *__futex = (futex);						      \
    int __val = atomic_exchange_rel (__futex, 0);			      \
									      \
    if (__builtin_expect (__val > 1, 0))				      \
      lll_futex_wake (__futex, 1, private);				      \
  }))
#define lll_unlock(futex, private) __lll_unlock(&(futex), private)


#define __lll_robust_unlock(futex, private)				      \
  ((void) ({								      \
    int *__futex = (futex);						      \
    int __val = atomic_exchange_rel (__futex, 0);			      \
									      \
    if (__builtin_expect (__val & FUTEX_WAITERS, 0))			      \
      lll_futex_wake (__futex, 1, private);				      \
  }))
#define lll_robust_unlock(futex, private) \
  __lll_robust_unlock(&(futex), private)


#define lll_islocked(futex) \
  (futex != 0)


/* Our internal lock implementation is identical to the binary-compatible
   mutex implementation. */

/* Initializers for lock.  */
#define LLL_LOCK_INITIALIZER		(0)
#define LLL_LOCK_INITIALIZER_LOCKED	(1)

/* The states of a lock are:
    0  -  untaken
    1  -  taken by one user
   >1  -  taken by more users */

/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex
   wakeup when the clone terminates.  The memory location contains the
   thread ID while the clone is running and is reset to zero
   afterwards.	*/
#define lll_wait_tid(tid) \
  do {							\
    __typeof (tid) __tid;				\
    while ((__tid = (tid)) != 0)			\
      lll_futex_wait (&(tid), __tid, LLL_SHARED);	\
  } while (0)

extern int __lll_timedwait_tid (int *, const struct timespec *)
     attribute_hidden;

#define lll_timedwait_tid(tid, abstime) \
  ({							\
    int __res = 0;					\
    if ((tid) != 0)					\
      __res = __lll_timedwait_tid (&(tid), (abstime));	\
    __res;						\
  })

/* Implement __libc_lock_lock using exchange_and_add, which expands into
   a single instruction on XLP processors.  We enable this for all MIPS
   processors as atomic_exchange_and_add_acq and
   atomic_compare_and_exchange_acq take the same time to execute.
   This is a simplified expansion of ({ lll_lock (NAME, LLL_PRIVATE); 0; }).

   Note: __lll_lock_wait_private() resets lock value to '2', which prevents
   unbounded increase of the lock value and [with billions of threads]
   overflow.  */
#define __libc_lock_lock(NAME)						\
  ({									\
    int *__futex = &(NAME);						\
    if (__builtin_expect (atomic_exchange_and_add_acq (__futex, 1), 0))	\
      __lll_lock_wait_private (__futex);				\
    0;									\
  })

#ifdef _MIPS_ARCH_XLP
/* The generic version using a single atomic_compare_and_exchange_acq takes
   less time for non-XLP processors, so we use below for XLP only.  */
# define __libc_lock_trylock(NAME)					\
  ({									\
  int *__futex = &(NAME);						\
  int __result = atomic_exchange_and_add_acq (__futex, 1);		\
  /* If __result == 0, we succeeded in acquiring the lock.		\
     If __result == 1, we switched the lock to 'contended' state, which	\
     will cause a [possibly unnecessary] call to lll_futex_wait.  This is \
     unlikely, so we accept the possible inefficiency.			\
     If __result >= 2, we need to set the lock to 'contended' state to avoid \
     unbounded increase from subsequent trylocks.  */			\
  if (__result >= 2)							\
    __result = atomic_exchange_acq (__futex, 2);			\
  __result;								\
  })
#endif

#endif	/* lowlevellock.h */