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198 lines
8.3 KiB
C
198 lines
8.3 KiB
C
/* Low-level locking access to futex facilities. Stub version.
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Copyright (C) 2014-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _LOWLEVELLOCK_FUTEX_H
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#define _LOWLEVELLOCK_FUTEX_H 1
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#ifndef __ASSEMBLER__
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# include <sysdep.h>
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# include <sysdep-cancel.h>
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# include <kernel-features.h>
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#endif
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#define FUTEX_WAIT 0
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#define FUTEX_WAKE 1
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#define FUTEX_REQUEUE 3
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#define FUTEX_CMP_REQUEUE 4
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#define FUTEX_WAKE_OP 5
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#define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE ((4 << 24) | 1)
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#define FUTEX_LOCK_PI 6
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#define FUTEX_UNLOCK_PI 7
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#define FUTEX_TRYLOCK_PI 8
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#define FUTEX_WAIT_BITSET 9
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#define FUTEX_WAKE_BITSET 10
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#define FUTEX_WAIT_REQUEUE_PI 11
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#define FUTEX_CMP_REQUEUE_PI 12
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#define FUTEX_PRIVATE_FLAG 128
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#define FUTEX_CLOCK_REALTIME 256
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#define FUTEX_BITSET_MATCH_ANY 0xffffffff
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/* Values for 'private' parameter of locking macros. Yes, the
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definition seems to be backwards. But it is not. The bit will be
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reversed before passing to the system call. */
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#define LLL_PRIVATE 0
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#define LLL_SHARED FUTEX_PRIVATE_FLAG
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#ifndef __ASSEMBLER__
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# if IS_IN (libc) || IS_IN (rtld)
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/* In libc.so or ld.so all futexes are private. */
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# define __lll_private_flag(fl, private) \
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({ \
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/* Prevent warnings in callers of this macro. */ \
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int __lll_private_flag_priv __attribute__ ((unused)); \
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__lll_private_flag_priv = (private); \
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((fl) | FUTEX_PRIVATE_FLAG); \
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})
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# else
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# define __lll_private_flag(fl, private) \
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(((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
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# endif
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# define lll_futex_syscall(nargs, futexp, op, ...) \
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({ \
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INTERNAL_SYSCALL_DECL (__err); \
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long int __ret = INTERNAL_SYSCALL (futex, __err, nargs, futexp, op, \
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__VA_ARGS__); \
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(__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret, __err)) \
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? -INTERNAL_SYSCALL_ERRNO (__ret, __err) : 0); \
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})
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/* For most of these macros, the return value is never really used.
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Nevertheless, the protocol is that each one returns a negated errno
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code for failure or zero for success. (Note that the corresponding
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Linux system calls can sometimes return positive values for success
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cases too. We never use those values.) */
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/* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP. */
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# define lll_futex_wait(futexp, val, private) \
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lll_futex_timed_wait (futexp, val, NULL, private)
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# define lll_futex_timed_wait(futexp, val, timeout, private) \
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lll_futex_syscall (4, futexp, \
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__lll_private_flag (FUTEX_WAIT, private), \
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val, timeout)
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/* Verify whether the supplied clockid is supported by
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lll_futex_clock_wait_bitset. */
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# define lll_futex_supported_clockid(clockid) \
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((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
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/* The kernel currently only supports CLOCK_MONOTONIC or
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CLOCK_REALTIME timeouts for FUTEX_WAIT_BITSET. We could attempt to
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convert others here but currently do not. */
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# define lll_futex_clock_wait_bitset(futexp, val, clockid, timeout, private) \
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({ \
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long int __ret; \
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if (lll_futex_supported_clockid (clockid)) \
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{ \
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const unsigned int clockbit = \
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(clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0; \
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const int op = \
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__lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private); \
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\
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__ret = lll_futex_syscall (6, futexp, op, val, \
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timeout, NULL /* Unused. */, \
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FUTEX_BITSET_MATCH_ANY); \
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} \
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else \
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__ret = -EINVAL; \
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__ret; \
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})
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/* Wake up up to NR waiters on FUTEXP. */
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# define lll_futex_wake(futexp, nr, private) \
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lll_futex_syscall (4, futexp, \
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__lll_private_flag (FUTEX_WAKE, private), nr, 0)
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/* Wake up up to NR_WAKE waiters on FUTEXP. Move up to NR_MOVE of the
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rest from waiting on FUTEXP to waiting on MUTEX (a different futex).
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Returns non-zero if error happened, zero if success. */
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# define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
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lll_futex_syscall (6, futexp, \
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__lll_private_flag (FUTEX_CMP_REQUEUE, private), \
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nr_wake, nr_move, mutex, val)
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/* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.
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Returns non-zero if error happened, zero if success. */
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# define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
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lll_futex_syscall (6, futexp, \
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__lll_private_flag (FUTEX_WAKE_OP, private), \
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nr_wake, nr_wake2, futexp2, \
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FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
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/* Priority Inheritance support. */
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#define lll_futex_timed_lock_pi(futexp, abstime, private) \
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lll_futex_syscall (4, futexp, \
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__lll_private_flag (FUTEX_LOCK_PI, private), \
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0, abstime)
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#define lll_futex_timed_unlock_pi(futexp, private) \
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lll_futex_syscall (4, futexp, \
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__lll_private_flag (FUTEX_UNLOCK_PI, private), \
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0, 0)
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/* Like lll_futex_wait (FUTEXP, VAL, PRIVATE) but with the expectation
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that lll_futex_cmp_requeue_pi (FUTEXP, _, _, MUTEX, _, PRIVATE) will
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be used to do the wakeup. Confers priority-inheritance behavior on
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the waiter. */
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# define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
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lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)
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/* Like lll_futex_wait_requeue_pi, but with a timeout. */
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# define lll_futex_timed_wait_requeue_pi(futexp, val, timeout, clockbit, \
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mutex, private) \
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lll_futex_syscall (5, futexp, \
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__lll_private_flag (FUTEX_WAIT_REQUEUE_PI \
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| (clockbit), private), \
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val, timeout, mutex)
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/* Like lll_futex_requeue, but pairs with lll_futex_wait_requeue_pi
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and inherits priority from the waiter. */
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# define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, \
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val, private) \
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lll_futex_syscall (6, futexp, \
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__lll_private_flag (FUTEX_CMP_REQUEUE_PI, \
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private), \
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nr_wake, nr_move, mutex, val)
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/* Like lll_futex_wait, but acting as a cancellable entrypoint. */
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# define lll_futex_wait_cancel(futexp, val, private) \
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({ \
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int __oldtype = CANCEL_ASYNC (); \
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long int __err = lll_futex_wait (futexp, val, LLL_SHARED); \
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CANCEL_RESET (__oldtype); \
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__err; \
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})
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/* Like lll_futex_timed_wait, but acting as a cancellable entrypoint. */
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# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
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({ \
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int __oldtype = CANCEL_ASYNC (); \
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long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
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CANCEL_RESET (__oldtype); \
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__err; \
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})
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#endif /* !__ASSEMBLER__ */
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#endif /* lowlevellock-futex.h */
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