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/* 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 */
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