codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * spin.h4 *	   Hardware-independent implementation of spinlocks.5 *6 *7 *	The hardware-independent interface to spinlocks is defined by the8 *	typedef "slock_t" and these macros:9 *10 *	void SpinLockInit(volatile slock_t *lock)11 *		Initialize a spinlock (to the unlocked state).12 *13 *	void SpinLockAcquire(volatile slock_t *lock)14 *		Acquire a spinlock, waiting if necessary.15 *		Time out and abort() if unable to acquire the lock in a16 *		"reasonable" amount of time --- typically ~ 1 minute.17 *18 *	void SpinLockRelease(volatile slock_t *lock)19 *		Unlock a previously acquired lock.20 *21 *	bool SpinLockFree(slock_t *lock)22 *		Tests if the lock is free. Returns true if free, false if locked.23 *		This does *not* change the state of the lock.24 *25 *	Callers must beware that the macro argument may be evaluated multiple26 *	times!27 *28 *	Load and store operations in calling code are guaranteed not to be29 *	reordered with respect to these operations, because they include a30 *	compiler barrier.  (Before PostgreSQL 9.5, callers needed to use a31 *	volatile qualifier to access data protected by spinlocks.)32 *33 *	Keep in mind the coding rule that spinlocks must not be held for more34 *	than a few instructions.  In particular, we assume it is not possible35 *	for a CHECK_FOR_INTERRUPTS() to occur while holding a spinlock, and so36 *	it is not necessary to do HOLD/RESUME_INTERRUPTS() in these macros.37 *38 *	These macros are implemented in terms of hardware-dependent macros39 *	supplied by s_lock.h.  There is not currently any extra functionality40 *	added by this header, but there has been in the past and may someday41 *	be again.42 *43 *44 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group45 * Portions Copyright (c) 1994, Regents of the University of California46 *47 * src/include/storage/spin.h48 *49 *-------------------------------------------------------------------------50 */51#ifndef SPIN_H52#define SPIN_H53 54#include "storage/s_lock.h"55#ifndef HAVE_SPINLOCKS56#include "storage/pg_sema.h"57#endif58 59 60#define SpinLockInit(lock)	S_INIT_LOCK(lock)61 62#define SpinLockAcquire(lock) S_LOCK(lock)63 64#define SpinLockRelease(lock) S_UNLOCK(lock)65 66#define SpinLockFree(lock)	S_LOCK_FREE(lock)67 68 69extern int	SpinlockSemas(void);70extern Size SpinlockSemaSize(void);71 72#ifndef HAVE_SPINLOCKS73extern void SpinlockSemaInit(void);74extern PGDLLIMPORT PGSemaphore *SpinlockSemaArray;75#endif76 77#endif							/* SPIN_H */78