mirror of
https://github.com/systemd/systemd.git
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437 lines
7.8 KiB
C
437 lines
7.8 KiB
C
/*
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Unix SMB/CIFS implementation.
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Samba database functions
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Copyright (C) Anton Blanchard 2001
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/* udev defines */
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#define STANDALONE
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#define TDB_DEBUG
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#define HAVE_MMAP 1
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#if HAVE_CONFIG_H
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#include <config.h>
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#endif
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#ifdef STANDALONE
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <time.h>
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#include <signal.h>
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#include "tdb.h"
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#include "spinlock.h"
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#define DEBUG
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#else
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#include "includes.h"
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#endif
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#ifdef USE_SPINLOCKS
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/*
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* ARCH SPECIFIC
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*/
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#if defined(SPARC_SPINLOCKS)
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static inline int __spin_trylock(spinlock_t *lock)
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{
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unsigned int result;
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asm volatile("ldstub [%1], %0"
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: "=r" (result)
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: "r" (lock)
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: "memory");
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return (result == 0) ? 0 : EBUSY;
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}
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static inline void __spin_unlock(spinlock_t *lock)
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{
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asm volatile("":::"memory");
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*lock = 0;
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}
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static inline void __spin_lock_init(spinlock_t *lock)
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{
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*lock = 0;
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}
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static inline int __spin_is_locked(spinlock_t *lock)
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{
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return (*lock != 0);
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}
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#elif defined(POWERPC_SPINLOCKS)
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static inline int __spin_trylock(spinlock_t *lock)
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{
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unsigned int result;
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__asm__ __volatile__(
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"1: lwarx %0,0,%1\n\
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cmpwi 0,%0,0\n\
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li %0,0\n\
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bne- 2f\n\
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li %0,1\n\
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stwcx. %0,0,%1\n\
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bne- 1b\n\
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isync\n\
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2:" : "=&r"(result)
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: "r"(lock)
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: "cr0", "memory");
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return (result == 1) ? 0 : EBUSY;
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}
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static inline void __spin_unlock(spinlock_t *lock)
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{
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asm volatile("eieio":::"memory");
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*lock = 0;
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}
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static inline void __spin_lock_init(spinlock_t *lock)
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{
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*lock = 0;
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}
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static inline int __spin_is_locked(spinlock_t *lock)
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{
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return (*lock != 0);
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}
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#elif defined(INTEL_SPINLOCKS)
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static inline int __spin_trylock(spinlock_t *lock)
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{
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int oldval;
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asm volatile("xchgl %0,%1"
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: "=r" (oldval), "=m" (*lock)
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: "0" (0)
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: "memory");
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return oldval > 0 ? 0 : EBUSY;
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}
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static inline void __spin_unlock(spinlock_t *lock)
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{
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asm volatile("":::"memory");
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*lock = 1;
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}
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static inline void __spin_lock_init(spinlock_t *lock)
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{
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*lock = 1;
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}
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static inline int __spin_is_locked(spinlock_t *lock)
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{
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return (*lock != 1);
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}
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#elif defined(MIPS_SPINLOCKS)
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static inline unsigned int load_linked(unsigned long addr)
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{
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unsigned int res;
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__asm__ __volatile__("ll\t%0,(%1)"
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: "=r" (res)
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: "r" (addr));
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return res;
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}
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static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
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{
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unsigned int res;
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__asm__ __volatile__("sc\t%0,(%2)"
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: "=r" (res)
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: "0" (value), "r" (addr));
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return res;
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}
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static inline int __spin_trylock(spinlock_t *lock)
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{
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unsigned int mw;
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do {
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mw = load_linked(lock);
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if (mw)
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return EBUSY;
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} while (!store_conditional(lock, 1));
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asm volatile("":::"memory");
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return 0;
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}
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static inline void __spin_unlock(spinlock_t *lock)
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{
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asm volatile("":::"memory");
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*lock = 0;
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}
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static inline void __spin_lock_init(spinlock_t *lock)
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{
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*lock = 0;
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}
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static inline int __spin_is_locked(spinlock_t *lock)
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{
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return (*lock != 0);
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}
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#else
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#error Need to implement spinlock code in spinlock.c
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#endif
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/*
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* OS SPECIFIC
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*/
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static void yield_cpu(void)
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{
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struct timespec tm;
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#ifdef USE_SCHED_YIELD
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sched_yield();
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#else
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/* Linux will busy loop for delays < 2ms on real time tasks */
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tm.tv_sec = 0;
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tm.tv_nsec = 2000000L + 1;
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nanosleep(&tm, NULL);
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#endif
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}
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static int this_is_smp(void)
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{
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return 0;
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}
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/*
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* GENERIC
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*/
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static int smp_machine = 0;
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static inline void __spin_lock(spinlock_t *lock)
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{
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int ntries = 0;
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while(__spin_trylock(lock)) {
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while(__spin_is_locked(lock)) {
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if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
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continue;
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yield_cpu();
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}
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}
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}
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static void __read_lock(tdb_rwlock_t *rwlock)
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{
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int ntries = 0;
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while(1) {
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__spin_lock(&rwlock->lock);
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if (!(rwlock->count & RWLOCK_BIAS)) {
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rwlock->count++;
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__spin_unlock(&rwlock->lock);
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return;
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}
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__spin_unlock(&rwlock->lock);
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while(rwlock->count & RWLOCK_BIAS) {
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if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
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continue;
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yield_cpu();
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}
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}
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}
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static void __write_lock(tdb_rwlock_t *rwlock)
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{
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int ntries = 0;
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while(1) {
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__spin_lock(&rwlock->lock);
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if (rwlock->count == 0) {
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rwlock->count |= RWLOCK_BIAS;
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__spin_unlock(&rwlock->lock);
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return;
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}
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__spin_unlock(&rwlock->lock);
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while(rwlock->count != 0) {
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if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
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continue;
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yield_cpu();
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}
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}
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}
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static void __write_unlock(tdb_rwlock_t *rwlock)
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{
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__spin_lock(&rwlock->lock);
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#ifdef DEBUG
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if (!(rwlock->count & RWLOCK_BIAS))
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fprintf(stderr, "bug: write_unlock\n");
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#endif
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rwlock->count &= ~RWLOCK_BIAS;
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__spin_unlock(&rwlock->lock);
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}
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static void __read_unlock(tdb_rwlock_t *rwlock)
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{
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__spin_lock(&rwlock->lock);
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#ifdef DEBUG
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if (!rwlock->count)
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fprintf(stderr, "bug: read_unlock\n");
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if (rwlock->count & RWLOCK_BIAS)
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fprintf(stderr, "bug: read_unlock\n");
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#endif
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rwlock->count--;
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__spin_unlock(&rwlock->lock);
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}
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/* TDB SPECIFIC */
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/* lock a list in the database. list -1 is the alloc list */
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int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
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{
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tdb_rwlock_t *rwlocks;
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if (!tdb->map_ptr) return -1;
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rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
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switch(rw_type) {
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case F_RDLCK:
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__read_lock(&rwlocks[list+1]);
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break;
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case F_WRLCK:
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__write_lock(&rwlocks[list+1]);
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break;
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default:
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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}
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return 0;
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}
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/* unlock the database. */
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int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
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{
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tdb_rwlock_t *rwlocks;
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if (!tdb->map_ptr) return -1;
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rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
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switch(rw_type) {
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case F_RDLCK:
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__read_unlock(&rwlocks[list+1]);
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break;
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case F_WRLCK:
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__write_unlock(&rwlocks[list+1]);
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break;
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default:
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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}
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return 0;
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}
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int tdb_create_rwlocks(int fd, unsigned int hash_size)
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{
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unsigned size, i;
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tdb_rwlock_t *rwlocks;
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size = (hash_size + 1) * sizeof(tdb_rwlock_t);
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rwlocks = malloc(size);
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if (!rwlocks)
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return -1;
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for(i = 0; i < hash_size+1; i++) {
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__spin_lock_init(&rwlocks[i].lock);
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rwlocks[i].count = 0;
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}
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/* Write it out (appending to end) */
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if (write(fd, rwlocks, size) != size) {
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free(rwlocks);
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return -1;
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}
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smp_machine = this_is_smp();
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free(rwlocks);
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return 0;
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}
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int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
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{
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tdb_rwlock_t *rwlocks;
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unsigned i;
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if (tdb->header.rwlocks == 0) return 0;
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if (!tdb->map_ptr) return -1;
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/* We're mmapped here */
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rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
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for(i = 0; i < tdb->header.hash_size+1; i++) {
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__spin_lock_init(&rwlocks[i].lock);
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rwlocks[i].count = 0;
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}
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return 0;
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}
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#else
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int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
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int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
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int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
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/* Non-spinlock version: remove spinlock pointer */
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int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
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{
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tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
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- (char *)&tdb->header);
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tdb->header.rwlocks = 0;
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if (lseek(tdb->fd, off, SEEK_SET) != off
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|| write(tdb->fd, (void *)&tdb->header.rwlocks,
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sizeof(tdb->header.rwlocks))
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!= sizeof(tdb->header.rwlocks))
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return -1;
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return 0;
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}
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#endif
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