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Get rid of the SpinLockAcquire/SpinLockAcquire_NoHoldoff distinction

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in favor of having just one set of macros that don't do HOLD/RESUME_INTERRUPTS
(hence, these correspond to the old SpinLockAcquire_NoHoldoff case).
Given our coding rules for spinlock use, there is no reason to allow
CHECK_FOR_INTERRUPTS to be done while holding a spinlock, and also there
is no situation where ImmediateInterruptOK will be true while holding a
spinlock.  Therefore doing HOLD/RESUME_INTERRUPTS while taking/releasing a
spinlock is just a waste of cycles.  Qingqing Zhou and Tom Lane.
This commit is contained in:
Tom Lane
2005-12-29 18:08:05 +00:00
parent e135d9631b
commit 195f164228
6 changed files with 80 additions and 112 deletions
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36
src/include/storage/spin.h
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@@ -14,17 +14,9 @@
* 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.
* Cancel/die interrupts are held off until the lock is released.
*
* void SpinLockRelease(volatile slock_t *lock)
* Unlock a previously acquired lock.
* Release the cancel/die interrupt holdoff.
*
* void SpinLockAcquire_NoHoldoff(volatile slock_t *lock)
* void SpinLockRelease_NoHoldoff(volatile slock_t *lock)
* Same as above, except no interrupt holdoff processing is done.
* This pair of macros may be used when there is a surrounding
* interrupt holdoff.
*
* bool SpinLockFree(slock_t *lock)
* Tests if the lock is free. Returns TRUE if free, FALSE if locked.
@@ -43,14 +35,21 @@
* 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.
* 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) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/spin.h,v 1.26 2005/10/13 06:17:34 neilc Exp $
* $PostgreSQL: pgsql/src/include/storage/spin.h,v 1.27 2005/12/29 18:08:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -58,26 +57,13 @@
#define SPIN_H
#include "storage/s_lock.h"
#include "miscadmin.h"
#define SpinLockInit(lock) S_INIT_LOCK(lock)
#define SpinLockAcquire(lock) \
do { \
HOLD_INTERRUPTS(); \
S_LOCK(lock); \
} while (0)
#define SpinLockAcquire(lock) S_LOCK(lock)
#define SpinLockAcquire_NoHoldoff(lock) S_LOCK(lock)
#define SpinLockRelease(lock) \
do { \
S_UNLOCK(lock); \
RESUME_INTERRUPTS(); \
} while (0)
#define SpinLockRelease_NoHoldoff(lock) S_UNLOCK(lock)
#define SpinLockRelease(lock) S_UNLOCK(lock)
#define SpinLockFree(lock) S_LOCK_FREE(lock)