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2014-08-12 Bernard Ogden <bernie.ogden@linaro.org> [BZ #16892] * sysdeps/nptl/lowlevellock.h (__lll_timedlock): Use atomic_compare_and_exchange_bool_acq rather than atomic_exchange_acq.
191 lines
8.1 KiB
C
191 lines
8.1 KiB
C
/* Low-level lock implementation. Generic futex-based version.
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Copyright (C) 2005-2014 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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<http://www.gnu.org/licenses/>. */
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#ifndef _LOWLEVELLOCK_H
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#define _LOWLEVELLOCK_H 1
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#include <atomic.h>
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#include <lowlevellock-futex.h>
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#define lll_trylock(lock) \
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atomic_compare_and_exchange_bool_acq (&(lock), 1, 0)
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#define lll_cond_trylock(lock) \
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atomic_compare_and_exchange_bool_acq (&(lock), 2, 0)
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extern void __lll_lock_wait_private (int *futex) attribute_hidden;
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extern void __lll_lock_wait (int *futex, int private) attribute_hidden;
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extern int __lll_robust_lock_wait (int *futex, int private) attribute_hidden;
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/* This is an expression rather than a statement even though its value is
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void, so that it can be used in a comma expression or as an expression
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that's cast to void. */
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#define __lll_lock(futex, private) \
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((void) \
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({ \
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int *__futex = (futex); \
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if (__glibc_unlikely \
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(atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \
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{ \
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if (__builtin_constant_p (private) && (private) == LLL_PRIVATE) \
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__lll_lock_wait_private (__futex); \
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else \
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__lll_lock_wait (__futex, private); \
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} \
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}))
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#define lll_lock(futex, private) \
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__lll_lock (&(futex), private)
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#define __lll_robust_lock(futex, id, private) \
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({ \
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int *__futex = (futex); \
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int __val = 0; \
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\
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if (__glibc_unlikely \
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(atomic_compare_and_exchange_bool_acq (__futex, id, 0))) \
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__val = __lll_robust_lock_wait (__futex, private); \
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__val; \
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})
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#define lll_robust_lock(futex, id, private) \
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__lll_robust_lock (&(futex), id, private)
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/* This is an expression rather than a statement even though its value is
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void, so that it can be used in a comma expression or as an expression
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that's cast to void. */
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#define __lll_cond_lock(futex, private) \
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((void) \
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({ \
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int *__futex = (futex); \
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if (__glibc_unlikely (atomic_exchange_acq (__futex, 2) != 0)) \
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__lll_lock_wait (__futex, private); \
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}))
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#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
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#define lll_robust_cond_lock(futex, id, private) \
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__lll_robust_lock (&(futex), (id) | FUTEX_WAITERS, private)
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extern int __lll_timedlock_wait (int *futex, const struct timespec *,
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int private) attribute_hidden;
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extern int __lll_robust_timedlock_wait (int *futex, const struct timespec *,
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int private) attribute_hidden;
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/* Take futex if it is untaken.
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Otherwise block until either we get the futex or abstime runs out. */
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#define __lll_timedlock(futex, abstime, private) \
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({ \
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int *__futex = (futex); \
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int __val = 0; \
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\
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if (__glibc_unlikely \
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(atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \
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__val = __lll_timedlock_wait (__futex, abstime, private); \
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__val; \
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})
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#define lll_timedlock(futex, abstime, private) \
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__lll_timedlock (&(futex), abstime, private)
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#define __lll_robust_timedlock(futex, abstime, id, private) \
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({ \
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int *__futex = (futex); \
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int __val = 0; \
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\
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if (__glibc_unlikely \
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(atomic_compare_and_exchange_bool_acq (__futex, id, 0))) \
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__val = __lll_robust_timedlock_wait (__futex, abstime, private); \
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__val; \
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})
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#define lll_robust_timedlock(futex, abstime, id, private) \
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__lll_robust_timedlock (&(futex), abstime, id, private)
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/* This is an expression rather than a statement even though its value is
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void, so that it can be used in a comma expression or as an expression
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that's cast to void. */
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#define __lll_unlock(futex, private) \
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((void) \
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({ \
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int *__futex = (futex); \
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int __oldval = atomic_exchange_rel (__futex, 0); \
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if (__glibc_unlikely (__oldval > 1)) \
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lll_futex_wake (__futex, 1, private); \
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}))
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#define lll_unlock(futex, private) \
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__lll_unlock (&(futex), private)
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/* This is an expression rather than a statement even though its value is
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void, so that it can be used in a comma expression or as an expression
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that's cast to void. */
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#define __lll_robust_unlock(futex, private) \
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((void) \
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({ \
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int *__futex = (futex); \
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int __oldval = atomic_exchange_rel (__futex, 0); \
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if (__glibc_unlikely (__oldval & FUTEX_WAITERS)) \
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lll_futex_wake (__futex, 1, private); \
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}))
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#define lll_robust_unlock(futex, private) \
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__lll_robust_unlock (&(futex), private)
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#define lll_islocked(futex) \
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((futex) != LLL_LOCK_INITIALIZER)
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/* Our internal lock implementation is identical to the binary-compatible
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mutex implementation. */
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/* Initializers for lock. */
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#define LLL_LOCK_INITIALIZER (0)
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#define LLL_LOCK_INITIALIZER_LOCKED (1)
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/* The states of a lock are:
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0 - untaken
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1 - taken by one user
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>1 - taken by more users */
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/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex
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wakeup when the clone terminates. The memory location contains the
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thread ID while the clone is running and is reset to zero
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afterwards. */
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#define lll_wait_tid(tid) \
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do { \
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__typeof (tid) __tid; \
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while ((__tid = (tid)) != 0) \
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lll_futex_wait (&(tid), __tid, LLL_SHARED);\
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} while (0)
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extern int __lll_timedwait_tid (int *, const struct timespec *)
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attribute_hidden;
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#define lll_timedwait_tid(tid, abstime) \
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({ \
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int __res = 0; \
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if ((tid) != 0) \
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__res = __lll_timedwait_tid (&(tid), (abstime)); \
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__res; \
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})
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#endif /* lowlevellock.h */
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