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8ec569479f
Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
78 lines
2.4 KiB
C
78 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* spin.h
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* Hardware-independent implementation of spinlocks.
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*
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*
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* The hardware-independent interface to spinlocks is defined by the
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* typedef "slock_t" and these macros:
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*
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* void SpinLockInit(volatile slock_t *lock)
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* Initialize a spinlock (to the unlocked state).
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*
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* void SpinLockAcquire(volatile slock_t *lock)
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* Acquire a spinlock, waiting if necessary.
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* Time out and abort() if unable to acquire the lock in a
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* "reasonable" amount of time --- typically ~ 1 minute.
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*
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* void SpinLockRelease(volatile slock_t *lock)
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* Unlock a previously acquired lock.
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*
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* bool SpinLockFree(slock_t *lock)
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* Tests if the lock is free. Returns true if free, false if locked.
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* This does *not* change the state of the lock.
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*
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* Callers must beware that the macro argument may be evaluated multiple
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* times!
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*
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* Load and store operations in calling code are guaranteed not to be
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* reordered with respect to these operations, because they include a
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* compiler barrier. (Before PostgreSQL 9.5, callers needed to use a
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* volatile qualifier to access data protected by spinlocks.)
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*
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* Keep in mind the coding rule that spinlocks must not be held for more
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* than a few instructions. In particular, we assume it is not possible
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* for a CHECK_FOR_INTERRUPTS() to occur while holding a spinlock, and so
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* it is not necessary to do HOLD/RESUME_INTERRUPTS() in these macros.
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*
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* These macros are implemented in terms of hardware-dependent macros
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* supplied by s_lock.h. There is not currently any extra functionality
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* added by this header, but there has been in the past and may someday
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* be again.
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*
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/spin.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SPIN_H
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#define SPIN_H
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#include "storage/s_lock.h"
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#ifndef HAVE_SPINLOCKS
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#include "storage/pg_sema.h"
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#endif
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#define SpinLockInit(lock) S_INIT_LOCK(lock)
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#define SpinLockAcquire(lock) S_LOCK(lock)
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#define SpinLockRelease(lock) S_UNLOCK(lock)
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#define SpinLockFree(lock) S_LOCK_FREE(lock)
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extern int SpinlockSemas(void);
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extern Size SpinlockSemaSize(void);
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#ifndef HAVE_SPINLOCKS
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extern void SpinlockSemaInit(void);
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extern PGDLLIMPORT PGSemaphore *SpinlockSemaArray;
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#endif
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#endif /* SPIN_H */
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