78 lines
2.4 KiB
C
78 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* spin.h
|
|
* Hardware-independent implementation of spinlocks.
|
|
*
|
|
*
|
|
* The hardware-independent interface to spinlocks is defined by the
|
|
* typedef "slock_t" and these macros:
|
|
*
|
|
* void SpinLockInit(volatile slock_t *lock)
|
|
* Initialize a spinlock (to the unlocked state).
|
|
*
|
|
* void SpinLockAcquire(volatile slock_t *lock)
|
|
* Acquire a spinlock, waiting if necessary.
|
|
* Time out and abort() if unable to acquire the lock in a
|
|
* "reasonable" amount of time --- typically ~ 1 minute.
|
|
*
|
|
* void SpinLockRelease(volatile slock_t *lock)
|
|
* Unlock a previously acquired lock.
|
|
*
|
|
* bool SpinLockFree(slock_t *lock)
|
|
* Tests if the lock is free. Returns true if free, false if locked.
|
|
* This does *not* change the state of the lock.
|
|
*
|
|
* Callers must beware that the macro argument may be evaluated multiple
|
|
* times!
|
|
*
|
|
* Load and store operations in calling code are guaranteed not to be
|
|
* reordered with respect to these operations, because they include a
|
|
* compiler barrier. (Before PostgreSQL 9.5, callers needed to use a
|
|
* volatile qualifier to access data protected by spinlocks.)
|
|
*
|
|
* Keep in mind the coding rule that spinlocks must not be held for more
|
|
* than a few instructions. In particular, we assume it is not possible
|
|
* for a CHECK_FOR_INTERRUPTS() to occur while holding a spinlock, and so
|
|
* it is not necessary to do HOLD/RESUME_INTERRUPTS() in these macros.
|
|
*
|
|
* These macros are implemented in terms of hardware-dependent macros
|
|
* supplied by s_lock.h. There is not currently any extra functionality
|
|
* added by this header, but there has been in the past and may someday
|
|
* be again.
|
|
*
|
|
*
|
|
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* src/include/storage/spin.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef SPIN_H
|
|
#define SPIN_H
|
|
|
|
#include "storage/s_lock.h"
|
|
#ifndef HAVE_SPINLOCKS
|
|
#include "storage/pg_sema.h"
|
|
#endif
|
|
|
|
|
|
#define SpinLockInit(lock) S_INIT_LOCK(lock)
|
|
|
|
#define SpinLockAcquire(lock) S_LOCK(lock)
|
|
|
|
#define SpinLockRelease(lock) S_UNLOCK(lock)
|
|
|
|
#define SpinLockFree(lock) S_LOCK_FREE(lock)
|
|
|
|
|
|
extern int SpinlockSemas(void);
|
|
extern Size SpinlockSemaSize(void);
|
|
|
|
#ifndef HAVE_SPINLOCKS
|
|
extern void SpinlockSemaInit(void);
|
|
extern PGDLLIMPORT PGSemaphore *SpinlockSemaArray;
|
|
#endif
|
|
|
|
#endif /* SPIN_H */
|