| /*------------------------------------------------------------------------- |
| * |
| * 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! |
| * |
| * CAUTION: Care must be taken to ensure that loads and stores of |
| * shared memory values are not rearranged around spinlock acquire |
| * and release. This is done using the "volatile" qualifier: the C |
| * standard states that loads and stores of volatile objects cannot |
| * be rearranged *with respect to other volatile objects*. The |
| * spinlock is always written through a volatile pointer by the |
| * spinlock macros, but this is not sufficient by itself: code that |
| * protects shared data with a spinlock MUST reference that shared |
| * data through a volatile pointer. |
| * |
| * 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) 1996-2009, PostgreSQL Global Development Group |
| * Portions Copyright (c) 1994, Regents of the University of California |
| * |
| * $PostgreSQL: pgsql/src/include/storage/spin.h,v 1.31 2009/01/01 17:24:01 momjian Exp $ |
| * |
| *------------------------------------------------------------------------- |
| */ |
| #ifndef SPIN_H |
| #define SPIN_H |
| |
| #include "storage/s_lock.h" |
| |
| |
| #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); |
| |
| #endif /* SPIN_H */ |