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/* Low-level locking access to futex facilities. Stub version.
Copyright (C) 2014-2020 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
<https://www.gnu.org/licenses/>. */
#ifndef _LOWLEVELLOCK_FUTEX_H
#define _LOWLEVELLOCK_FUTEX_H 1
#ifndef __ASSEMBLER__
# include <sysdep.h>
# include <sysdep-cancel.h>
# include <kernel-features.h>
#endif
#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
#ifndef __ASSEMBLER__
# if IS_IN (libc) || IS_IN (rtld)
/* In libc.so or ld.so all futexes are private. */
# define __lll_private_flag(fl, private) \
({ \
/* Prevent warnings in callers of this macro. */ \
int __lll_private_flag_priv __attribute__ ((unused)); \
__lll_private_flag_priv = (private); \
((fl) | FUTEX_PRIVATE_FLAG); \
})
# else
# define __lll_private_flag(fl, private) \
(((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
# endif
# define lll_futex_syscall(nargs, futexp, op, ...) \
({ \
INTERNAL_SYSCALL_DECL (__err); \
long int __ret = INTERNAL_SYSCALL (futex, __err, nargs, futexp, op, \
__VA_ARGS__); \
(__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret, __err)) \
? -INTERNAL_SYSCALL_ERRNO (__ret, __err) : 0); \
})
/* For most of these macros, the return value is never really used.
Nevertheless, the protocol is that each one returns a negated errno
code for failure or zero for success. (Note that the corresponding
Linux system calls can sometimes return positive values for success
cases too. We never use those values.) */
/* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP. */
# define lll_futex_wait(futexp, val, private) \
lll_futex_timed_wait (futexp, val, NULL, private)
# define lll_futex_timed_wait(futexp, val, timeout, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_WAIT, private), \
val, timeout)
/* Verify whether the supplied clockid is supported by
lll_futex_clock_wait_bitset. */
# define lll_futex_supported_clockid(clockid) \
((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
/* The kernel currently only supports CLOCK_MONOTONIC or
CLOCK_REALTIME timeouts for FUTEX_WAIT_BITSET. We could attempt to
convert others here but currently do not. */
# define lll_futex_clock_wait_bitset(futexp, val, clockid, timeout, private) \
({ \
long int __ret; \
if (lll_futex_supported_clockid (clockid)) \
{ \
const unsigned int clockbit = \
(clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0; \
const int op = \
__lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private); \
\
__ret = lll_futex_syscall (6, futexp, op, val, \
timeout, NULL /* Unused. */, \
FUTEX_BITSET_MATCH_ANY); \
} \
else \
__ret = -EINVAL; \
__ret; \
})
/* Wake up up to NR waiters on FUTEXP. */
# define lll_futex_wake(futexp, nr, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_WAKE, private), nr, 0)
/* Wake up up to NR_WAKE waiters on FUTEXP. Move up to NR_MOVE of the
rest from waiting on FUTEXP to waiting on MUTEX (a different futex).
Returns non-zero if error happened, zero if success. */
# define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_CMP_REQUEUE, private), \
nr_wake, nr_move, mutex, val)
/* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.
Returns non-zero if error happened, zero if success. */
# define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_WAKE_OP, private), \
nr_wake, nr_wake2, futexp2, \
FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
/* Priority Inheritance support. */
#define lll_futex_timed_lock_pi(futexp, abstime, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_LOCK_PI, private), \
0, abstime)
#define lll_futex_timed_unlock_pi(futexp, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_UNLOCK_PI, private), \
0, 0)
/* Like lll_futex_wait (FUTEXP, VAL, PRIVATE) but with the expectation
that lll_futex_cmp_requeue_pi (FUTEXP, _, _, MUTEX, _, PRIVATE) will
be used to do the wakeup. Confers priority-inheritance behavior on
the waiter. */
# define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)
/* Like lll_futex_wait_requeue_pi, but with a timeout. */
# define lll_futex_timed_wait_requeue_pi(futexp, val, timeout, clockbit, \
mutex, private) \
lll_futex_syscall (5, futexp, \
__lll_private_flag (FUTEX_WAIT_REQUEUE_PI \
| (clockbit), private), \
val, timeout, mutex)
/* Like lll_futex_requeue, but pairs with lll_futex_wait_requeue_pi
and inherits priority from the waiter. */
# define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, \
val, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_CMP_REQUEUE_PI, \
private), \
nr_wake, nr_move, mutex, val)
/* Like lll_futex_wait, but acting as a cancellable entrypoint. */
# define lll_futex_wait_cancel(futexp, val, private) \
({ \
int __oldtype = CANCEL_ASYNC (); \
long int __err = lll_futex_wait (futexp, val, LLL_SHARED); \
CANCEL_RESET (__oldtype); \
__err; \
})
/* Like lll_futex_timed_wait, but acting as a cancellable entrypoint. */
# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
({ \
int __oldtype = CANCEL_ASYNC (); \
long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
CANCEL_RESET (__oldtype); \
__err; \
})
#endif /* !__ASSEMBLER__ */
#endif /* lowlevellock-futex.h */
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