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/* Copyright (C) 2021 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/*!
* \brief Multiplatform spinlock.
*/
#pragma once
#if (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
/* Not tested and activated yet. */
/* #define HAVE_STDATOMIC */
#endif
#if defined(__APPLE__)
# if defined(MAC_OS_X_VERSION_10_12) || \
MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_12
# define APPLE_SPIN_NEW
# else
# define APPLE_SPIN_OLD
# endif /* MAC_OS_X_VERSION_10_12 ... */
#endif /* __APPLE__ */
#if defined(HAVE_SYNC_ATOMIC) || defined(HAVE_ATOMIC)
# include <stdbool.h>
#elif defined(HAVE_STDATOMIC)
# include <stdbool.h>
# include <stdatomic.h>
#elif defined(APPLE_SPIN_NEW)
# include <os/lock.h>
#elif defined(APPLE_SPIN_OLD)
# include <libkern/OSAtomic.h>
#else /* POSIX pthread spinlock. */
# include <pthread.h>
#endif
/*! \brief Spinlock lock variable type. */
typedef
#if defined(HAVE_SYNC_ATOMIC) || defined(HAVE_ATOMIC)
bool /*!< Spinlock lock - a simple & fast atomic version. */
#elif defined(HAVE_STDATOMIC)
atomic_bool /*!< Spinlock lock - a simple & fast atomic version, C11 */
#elif defined(APPLE_SPIN_NEW)
os_unfair_lock /*!< Spinlock lock - a newer macOS version (macOS >= 10.12). */
#elif defined(APPLE_SPIN_OLD)
OSSpinLock /*!< Spinlock lock - an older macOS version (macOS < 10.12). */
#else /* POSIX */
pthread_spinlock_t /*!< Spinlock lock - a POSIX pthread version. */
#endif
knot_spin_t;
/*! \brief Initialize the spinlock pointed to by the parameter "lock". */
static inline void knot_spin_init(knot_spin_t *lock)
{
#if defined(HAVE_SYNC_ATOMIC) || defined(HAVE_ATOMIC)
*lock = false;
#elif defined(HAVE_STDATOMIC)
atomic_init(lock, false);
#elif defined(APPLE_SPIN_NEW)
*lock = OS_UNFAIR_LOCK_INIT;
#elif defined(APPLE_SPIN_OLD)
*lock = OS_SPINLOCK_INIT;
#else /* POSIX */
pthread_spin_init(lock, PTHREAD_PROCESS_PRIVATE);
#endif
}
/*! \brief Destroy the spinlock pointed to by the parameter "lock". */
static inline void knot_spin_destroy(knot_spin_t *lock)
{
#if defined(HAVE_SYNC_ATOMIC) || defined(HAVE_ATOMIC) || defined(HAVE_STDATOMIC) || \
defined(APPLE_SPIN_NEW) || defined(APPLE_SPIN_OLD)
/* Nothing needed here. */
#else /* POSIX */
pthread_spin_destroy(lock);
#endif
}
/*! \brief Lock the spinlock pointed to by the parameter "lock". */
static inline void knot_spin_lock(knot_spin_t *lock)
{
#if defined(HAVE_SYNC_ATOMIC)
while (__sync_lock_test_and_set(lock, 1)) {
}
#elif defined(HAVE_ATOMIC)
int expected = 0;
while (!__atomic_compare_exchange_n(lock, &expected, 1, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED)) {
expected = 0;
}
#elif defined(HAVE_STDATOMIC)
int expected = 0;
while (!atomic_compare_exchange_strong(lock, &expected, false)) {
expected = 0;
}
#elif defined(APPLE_SPIN_NEW)
os_unfair_lock_lock(lock);
#elif defined(APPLE_SPIN_OLD)
OSSpinLockLock(lock);
#else /* POSIX */
pthread_spin_lock(lock);
#endif
}
/*! \brief Unlock the spinlock pointed to by the parameter "lock". */
static inline void knot_spin_unlock(knot_spin_t *lock)
{
#if defined(HAVE_SYNC_ATOMIC)
__sync_lock_release(lock);
#elif defined(HAVE_ATOMIC)
__atomic_clear(lock, __ATOMIC_RELAXED);
#elif defined(HAVE_STDATOMIC)
atomic_store(lock, false);
#elif defined(APPLE_SPIN_NEW)
os_unfair_lock_unlock(lock);
#elif defined(APPLE_SPIN_OLD)
OSSpinLockUnlock(lock);
#else /* POSIX */
pthread_spin_unlock(lock);
#endif
}
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