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/* Low-level lock implementation. Generic futex-based version.
Copyright (C) 2005-2014 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 <atomic.h>
#include <lowlevellock-futex.h>
#define lll_trylock(lock) \
atomic_compare_and_exchange_bool_acq (&(lock), 1, 0)
#define lll_cond_trylock(lock) \
atomic_compare_and_exchange_bool_acq (&(lock), 2, 0)
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;
/* This is an expression rather than a statement even though its value is
void, so that it can be used in a comma expression or as an expression
that's cast to void. */
#define __lll_lock(futex, private) \
((void) \
({ \
int *__futex = (futex); \
if (__glibc_unlikely \
(atomic_compare_and_exchange_bool_acq (__futex, 1, 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 (__glibc_unlikely \
(atomic_compare_and_exchange_bool_acq (__futex, id, 0))) \
__val = __lll_robust_lock_wait (__futex, private); \
__val; \
})
#define lll_robust_lock(futex, id, private) \
__lll_robust_lock (&(futex), id, private)
/* This is an expression rather than a statement even though its value is
void, so that it can be used in a comma expression or as an expression
that's cast to void. */
#define __lll_cond_lock(futex, private) \
((void) \
({ \
int *__futex = (futex); \
if (__glibc_unlikely (atomic_exchange_acq (__futex, 2) != 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;
/* Take futex if it is untaken.
Otherwise block until either we get the futex or abstime runs out. */
#define __lll_timedlock(futex, abstime, private) \
({ \
int *__futex = (futex); \
int __val = 0; \
\
if (__glibc_unlikely \
(atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \
__val = __lll_timedlock_wait (__futex, abstime, private); \
__val; \
})
#define lll_timedlock(futex, abstime, private) \
__lll_timedlock (&(futex), abstime, private)
#define __lll_robust_timedlock(futex, abstime, id, private) \
({ \
int *__futex = (futex); \
int __val = 0; \
\
if (__glibc_unlikely \
(atomic_compare_and_exchange_bool_acq (__futex, id, 0))) \
__val = __lll_robust_timedlock_wait (__futex, abstime, private); \
__val; \
})
#define lll_robust_timedlock(futex, abstime, id, private) \
__lll_robust_timedlock (&(futex), abstime, id, private)
/* This is an expression rather than a statement even though its value is
void, so that it can be used in a comma expression or as an expression
that's cast to void. */
#define __lll_unlock(futex, private) \
((void) \
({ \
int *__futex = (futex); \
int __oldval = atomic_exchange_rel (__futex, 0); \
if (__glibc_unlikely (__oldval > 1)) \
lll_futex_wake (__futex, 1, private); \
}))
#define lll_unlock(futex, private) \
__lll_unlock (&(futex), private)
/* This is an expression rather than a statement even though its value is
void, so that it can be used in a comma expression or as an expression
that's cast to void. */
#define __lll_robust_unlock(futex, private) \
((void) \
({ \
int *__futex = (futex); \
int __oldval = atomic_exchange_rel (__futex, 0); \
if (__glibc_unlikely (__oldval & FUTEX_WAITERS)) \
lll_futex_wake (__futex, 1, private); \
}))
#define lll_robust_unlock(futex, private) \
__lll_robust_unlock (&(futex), private)
#define lll_islocked(futex) \
((futex) != LLL_LOCK_INITIALIZER)
/* 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; \
})
#endif /* lowlevellock.h */
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