433 lines
9.6 KiB
C
433 lines
9.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* s_lock.h
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* This file contains the implementation (if any) for spinlocks.
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/include/storage/s_lock.h,v 1.73 2000/10/22 22:15:03 petere Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* DESCRIPTION
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* The public macros that must be provided are:
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*
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* void S_INIT_LOCK(slock_t *lock)
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*
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* void S_LOCK(slock_t *lock)
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*
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* void S_UNLOCK(slock_t *lock)
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*
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* void S_LOCK_FREE(slock_t *lock)
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* Tests if the lock is free. Returns non-zero if free, 0 if locked.
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*
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* The S_LOCK() macro implements a primitive but still useful random
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* backoff to avoid hordes of busywaiting lockers chewing CPU.
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*
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* Effectively:
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* void
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* S_LOCK(slock_t *lock)
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* {
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* while (TAS(lock))
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* {
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* // back off the cpu for a semi-random short time
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* }
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* }
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*
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* This implementation takes advantage of a tas function written
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* (in assembly language) on machines that have a native test-and-set
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* instruction. Alternative mutex implementations may also be used.
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* This function is hidden under the TAS macro to allow substitutions.
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*
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* #define TAS(lock) tas(lock)
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* int tas(slock_t *lock) // True if lock already set
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*
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* There are default implementations for all these macros at the bottom
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* of this file. Check if your platform can use these or needs to
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* override them.
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*
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* NOTES
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* If none of this can be done, POSTGRES will default to using
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* System V semaphores (and take a large performance hit -- around 40%
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* of its time on a DS5000/240 is spent in semop(3)...).
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*
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* AIX has a test-and-set but the recommended interface is the cs(3)
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* system call. This provides an 8-instruction (plus system call
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* overhead) uninterruptible compare-and-set operation. True
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* spinlocks might be faster but using cs(3) still speeds up the
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* regression test suite by about 25%. I don't have an assembler
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* manual for POWER in any case.
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*
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*/
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#if !defined(S_LOCK_H)
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#define S_LOCK_H
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#include "storage/ipc.h"
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extern void s_lock_sleep(unsigned spin);
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#if defined(HAS_TEST_AND_SET)
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#if defined(__GNUC__)
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/*************************************************************************
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* All the gcc inlines
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*/
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#if defined(__i386__)
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register slock_t _res = 1;
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__asm__("lock; xchgb %0,%1": "=q"(_res), "=m"(*lock):"0"(_res));
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return (int) _res;
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}
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#endif /* __i386__ */
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#ifdef __ia64__
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas (volatile slock_t *lock)
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{
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long int ret;
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__asm__ __volatile__(
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"xchg4 %0=%1,%2"
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: "=r"(ret), "=m"(*lock)
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: "r"(1), "1"(*lock)
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: "memory");
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return (int) ret;
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}
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#endif /* __ia64__ */
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#if defined(__arm__) || defined(__arm__)
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register slock_t _res = 1;
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__asm__("swpb %0, %0, [%3]": "=r"(_res), "=m"(*lock):"0"(_res), "r" (lock));
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return (int) _res;
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}
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#endif /* __arm__ */
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#if defined(__sparc__)
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register slock_t _res = 1;
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__asm__("ldstub [%2], %0" \
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: "=r"(_res), "=m"(*lock) \
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: "r"(lock));
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return (int) _res;
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}
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#endif /* __sparc__ */
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#if defined(__mc68000__) && defined(__linux__)
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register int rv;
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__asm__ __volatile__ (
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"tas %1; sne %0"
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: "=d" (rv), "=m"(*lock)
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: "1" (*lock)
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: "cc" );
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return rv;
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}
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#endif /* defined(__mc68000__) && defined(__linux__) */
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#if defined(NEED_VAX_TAS_ASM)
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/*
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* VAXen -- even multiprocessor ones
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* (thanks to Tom Ivar Helbekkmo)
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*/
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#define TAS(lock) tas(lock)
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typedef unsigned char slock_t;
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register _res;
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__asm__(" movl $1, r0 \
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bbssi $0, (%1), 1 f \
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clrl r0 \
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1: movl r0, %0 "
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: "=r"(_res) /* return value, in register */
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: "r"(lock) /* argument, 'lock pointer', in register */
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: "r0"); /* inline code uses this register */
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return (int) _res;
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}
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#endif /* NEED_VAX_TAS_ASM */
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#if defined(NEED_NS32K_TAS_ASM)
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#define TAS(lock) tas(lock)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register _res;
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__asm__("sbitb 0, %0 \n\
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sfsd %1"
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: "=m"(*lock), "=r"(_res));
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return (int) _res;
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}
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#endif /* NEED_NS32K_TAS_ASM */
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#else /* __GNUC__ */
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/***************************************************************************
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* All non gcc
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*/
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#if defined(__QNX__)
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/*
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* QNX 4
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*
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* Note that slock_t under QNX is sem_t instead of char
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*/
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#define TAS(lock) (sem_trywait((lock)) < 0)
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#define S_UNLOCK(lock) sem_post((lock))
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#define S_INIT_LOCK(lock) sem_init((lock), 1, 1)
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#define S_LOCK_FREE(lock) (lock)->value
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#endif /* __QNX__ */
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#if defined(NEED_I386_TAS_ASM)
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/* non gcc i386 based things */
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#if defined(USE_UNIVEL_CC)
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#define TAS(lock) tas(lock)
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asm int
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tas(volatile slock_t *s_lock)
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{
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/* UNIVEL wants %mem in column 1, so we don't pg_indent this file */
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%mem s_lock
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pushl %ebx
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movl s_lock, %ebx
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movl $255, %eax
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lock
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xchgb %al, (%ebx)
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popl %ebx
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}
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#endif /* USE_UNIVEL_CC */
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#endif /* NEED_I386_TAS_ASM */
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#endif /* defined(__GNUC__) */
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/*************************************************************************
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* These are the platforms that have common code for gcc and non-gcc
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*/
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#if defined(__alpha)
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#if defined(__osf__)
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/*
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* OSF/1 (Alpha AXP)
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*
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* Note that slock_t on the Alpha AXP is msemaphore instead of char
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* (see storage/ipc.h).
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*/
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#include <alpha/builtins.h>
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#if 0
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#define TAS(lock) (msem_lock((lock), MSEM_IF_NOWAIT) < 0)
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#define S_UNLOCK(lock) msem_unlock((lock), 0)
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#define S_INIT_LOCK(lock) msem_init((lock), MSEM_UNLOCKED)
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#define S_LOCK_FREE(lock) (!(lock)->msem_state)
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#else
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#define TAS(lock) (__INTERLOCKED_TESTBITSS_QUAD((lock),0))
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#endif
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#else /* i.e. not __osf__ */
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#define TAS(lock) tas(lock)
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#define S_UNLOCK(lock) do { __asm__("mb"); *(lock) = 0; } while (0)
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static __inline__ int
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tas(volatile slock_t *lock)
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{
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register slock_t _res;
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__asm__(" ldq $0, %0 \n\
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bne $0, 3f \n\
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ldq_l $0, %0 \n\
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bne $0, 3f \n\
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or $31, 1, $0 \n\
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stq_c $0, %0 \n\
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beq $0, 2f \n\
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bis $31, $31, %1 \n\
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mb \n\
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jmp $31, 4f \n\
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2: or $31, 1, $0 \n\
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3: bis $0, $0, %1 \n\
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4: nop ": "=m"(*lock), "=r"(_res): :"0");
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return (int) _res;
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}
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#endif /* __osf__ */
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#endif /* __alpha */
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#if defined(__hpux)
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/*
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* HP-UX (PA-RISC)
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*
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* Note that slock_t on PA-RISC is a structure instead of char
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* (see include/port/hpux.h).
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*
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* a "set" slock_t has a single word cleared. a "clear" slock_t has
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* all words set to non-zero. tas() in tas.s
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*/
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#define S_UNLOCK(lock) \
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do { \
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volatile slock_t *lock_ = (volatile slock_t *) (lock); \
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lock_->sema[0] = lock_->sema[1] = lock_->sema[2] = lock_->sema[3] = -1; \
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} while (0)
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#define S_LOCK_FREE(lock) ( *(int *) (((long) (lock) + 15) & ~15) != 0)
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#endif /* __hpux */
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#if defined(__sgi)
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/*
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* SGI IRIX 5
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* slock_t is defined as a unsigned long. We use the standard SGI
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* mutex API.
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*
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* The following comment is left for historical reasons, but is probably
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* not a good idea since the mutex ABI is supported.
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*
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* This stuff may be supplemented in the future with Masato Kataoka's MIPS-II
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* assembly from his NECEWS SVR4 port, but we probably ought to retain this
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* for the R3000 chips out there.
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*/
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#include "mutex.h"
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#define TAS(lock) (test_and_set(lock,1))
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#define S_UNLOCK(lock) (test_then_and(lock,0))
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#define S_INIT_LOCK(lock) (test_then_and(lock,0))
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#define S_LOCK_FREE(lock) (test_then_add(lock,0) == 0)
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#endif /* __sgi */
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#if defined(sinix)
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/*
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* SINIX / Reliant UNIX
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* slock_t is defined as a struct abilock_t, which has a single unsigned long
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* member. (Basically same as SGI)
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*
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*/
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#define TAS(lock) (!acquire_lock(lock))
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#define S_UNLOCK(lock) release_lock(lock)
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#define S_INIT_LOCK(lock) init_lock(lock)
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#define S_LOCK_FREE(lock) (stat_lock(lock) == UNLOCKED)
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#endif /* sinix */
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#if defined(_AIX)
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/*
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* AIX (POWER)
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*
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* Note that slock_t on POWER/POWER2/PowerPC is int instead of char
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* (see storage/ipc.h).
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*/
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#define TAS(lock) cs((int *) (lock), 0, 1)
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#endif /* _AIX */
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#if defined (nextstep)
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/*
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* NEXTSTEP (mach)
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* slock_t is defined as a struct mutex.
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*/
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#define S_LOCK(lock) mutex_lock(lock)
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#define S_UNLOCK(lock) mutex_unlock(lock)
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#define S_INIT_LOCK(lock) mutex_init(lock)
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/* For Mach, we have to delve inside the entrails of `struct mutex'. Ick! */
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#define S_LOCK_FREE(alock) ((alock)->lock == 0)
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#endif /* nextstep */
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/****************************************************************************
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* Default Definitions - override these above as needed.
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*/
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#if !defined(S_LOCK)
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extern void s_lock(volatile slock_t *lock, const char *file, const int line);
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#define S_LOCK(lock) \
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do { \
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if (TAS((volatile slock_t *) lock)) \
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s_lock((volatile slock_t *) lock, __FILE__, __LINE__); \
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} while (0)
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#endif /* S_LOCK */
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#if !defined(S_LOCK_FREE)
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#define S_LOCK_FREE(lock) (*(lock) == 0)
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#endif /* S_LOCK_FREE */
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#if !defined(S_UNLOCK)
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#define S_UNLOCK(lock) (*(lock) = 0)
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#endif /* S_UNLOCK */
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#if !defined(S_INIT_LOCK)
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#define S_INIT_LOCK(lock) S_UNLOCK(lock)
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#endif /* S_INIT_LOCK */
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#if !defined(TAS)
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int tas(volatile slock_t *lock); /* port/.../tas.s, or
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* s_lock.c */
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#define TAS(lock) tas((volatile slock_t *) lock)
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#endif /* TAS */
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#endif /* HAS_TEST_AND_SET */
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#endif /* S_LOCK_H */
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