diff options
Diffstat (limited to 'source3/tdb/spinlock.c')
-rw-r--r-- | source3/tdb/spinlock.c | 429 |
1 files changed, 429 insertions, 0 deletions
diff --git a/source3/tdb/spinlock.c b/source3/tdb/spinlock.c new file mode 100644 index 0000000000..74472854cf --- /dev/null +++ b/source3/tdb/spinlock.c @@ -0,0 +1,429 @@ +/* + Unix SMB/CIFS implementation. + Samba database functions + Copyright (C) Anton Blanchard 2001 + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. +*/ +#if HAVE_CONFIG_H +#include <config.h> +#endif + +#if STANDALONE +#include <stdlib.h> +#include <stdio.h> +#include <unistd.h> +#include <string.h> +#include <fcntl.h> +#include <errno.h> +#include <sys/stat.h> +#include <time.h> +#include "tdb.h" +#include "spinlock.h" + +#define DEBUG +#else +#include "includes.h" +#endif + +#ifdef USE_SPINLOCKS + +/* + * ARCH SPECIFIC + */ + +#if defined(SPARC_SPINLOCKS) + +static inline int __spin_trylock(spinlock_t *lock) +{ + unsigned int result; + + asm volatile("ldstub [%1], %0" + : "=r" (result) + : "r" (lock) + : "memory"); + + return (result == 0) ? 0 : EBUSY; +} + +static inline void __spin_unlock(spinlock_t *lock) +{ + asm volatile("":::"memory"); + *lock = 0; +} + +static inline void __spin_lock_init(spinlock_t *lock) +{ + *lock = 0; +} + +static inline int __spin_is_locked(spinlock_t *lock) +{ + return (*lock != 0); +} + +#elif defined(POWERPC_SPINLOCKS) + +static inline int __spin_trylock(spinlock_t *lock) +{ + unsigned int result; + + __asm__ __volatile__( +"1: lwarx %0,0,%1\n\ + cmpwi 0,%0,0\n\ + li %0,0\n\ + bne- 2f\n\ + li %0,1\n\ + stwcx. %0,0,%1\n\ + bne- 1b\n\ + isync\n\ +2:" : "=&r"(result) + : "r"(lock) + : "cr0", "memory"); + + return (result == 1) ? 0 : EBUSY; +} + +static inline void __spin_unlock(spinlock_t *lock) +{ + asm volatile("eieio":::"memory"); + *lock = 0; +} + +static inline void __spin_lock_init(spinlock_t *lock) +{ + *lock = 0; +} + +static inline int __spin_is_locked(spinlock_t *lock) +{ + return (*lock != 0); +} + +#elif defined(INTEL_SPINLOCKS) + +static inline int __spin_trylock(spinlock_t *lock) +{ + int oldval; + + asm volatile("xchgl %0,%1" + : "=r" (oldval), "=m" (*lock) + : "0" (0) + : "memory"); + + return oldval > 0 ? 0 : EBUSY; +} + +static inline void __spin_unlock(spinlock_t *lock) +{ + asm volatile("":::"memory"); + *lock = 1; +} + +static inline void __spin_lock_init(spinlock_t *lock) +{ + *lock = 1; +} + +static inline int __spin_is_locked(spinlock_t *lock) +{ + return (*lock != 1); +} + +#elif defined(MIPS_SPINLOCKS) + +static inline unsigned int load_linked(unsigned long addr) +{ + unsigned int res; + + __asm__ __volatile__("ll\t%0,(%1)" + : "=r" (res) + : "r" (addr)); + + return res; +} + +static inline unsigned int store_conditional(unsigned long addr, unsigned int value) +{ + unsigned int res; + + __asm__ __volatile__("sc\t%0,(%2)" + : "=r" (res) + : "0" (value), "r" (addr)); + return res; +} + +static inline int __spin_trylock(spinlock_t *lock) +{ + unsigned int mw; + + do { + mw = load_linked(lock); + if (mw) + return EBUSY; + } while (!store_conditional(lock, 1)); + + asm volatile("":::"memory"); + + return 0; +} + +static inline void __spin_unlock(spinlock_t *lock) +{ + asm volatile("":::"memory"); + *lock = 0; +} + +static inline void __spin_lock_init(spinlock_t *lock) +{ + *lock = 0; +} + +static inline int __spin_is_locked(spinlock_t *lock) +{ + return (*lock != 0); +} + +#else +#error Need to implement spinlock code in spinlock.c +#endif + +/* + * OS SPECIFIC + */ + +static void yield_cpu(void) +{ + struct timespec tm; + +#ifdef USE_SCHED_YIELD + sched_yield(); +#else + /* Linux will busy loop for delays < 2ms on real time tasks */ + tm.tv_sec = 0; + tm.tv_nsec = 2000000L + 1; + nanosleep(&tm, NULL); +#endif +} + +static int this_is_smp(void) +{ + return 0; +} + +/* + * GENERIC + */ + +static int smp_machine = 0; + +static inline void __spin_lock(spinlock_t *lock) +{ + int ntries = 0; + + while(__spin_trylock(lock)) { + while(__spin_is_locked(lock)) { + if (smp_machine && ntries++ < MAX_BUSY_LOOPS) + continue; + yield_cpu(); + } + } +} + +static void __read_lock(tdb_rwlock_t *rwlock) +{ + int ntries = 0; + + while(1) { + __spin_lock(&rwlock->lock); + + if (!(rwlock->count & RWLOCK_BIAS)) { + rwlock->count++; + __spin_unlock(&rwlock->lock); + return; + } + + __spin_unlock(&rwlock->lock); + + while(rwlock->count & RWLOCK_BIAS) { + if (smp_machine && ntries++ < MAX_BUSY_LOOPS) + continue; + yield_cpu(); + } + } +} + +static void __write_lock(tdb_rwlock_t *rwlock) +{ + int ntries = 0; + + while(1) { + __spin_lock(&rwlock->lock); + + if (rwlock->count == 0) { + rwlock->count |= RWLOCK_BIAS; + __spin_unlock(&rwlock->lock); + return; + } + + __spin_unlock(&rwlock->lock); + + while(rwlock->count != 0) { + if (smp_machine && ntries++ < MAX_BUSY_LOOPS) + continue; + yield_cpu(); + } + } +} + +static void __write_unlock(tdb_rwlock_t *rwlock) +{ + __spin_lock(&rwlock->lock); + +#ifdef DEBUG + if (!(rwlock->count & RWLOCK_BIAS)) + fprintf(stderr, "bug: write_unlock\n"); +#endif + + rwlock->count &= ~RWLOCK_BIAS; + __spin_unlock(&rwlock->lock); +} + +static void __read_unlock(tdb_rwlock_t *rwlock) +{ + __spin_lock(&rwlock->lock); + +#ifdef DEBUG + if (!rwlock->count) + fprintf(stderr, "bug: read_unlock\n"); + + if (rwlock->count & RWLOCK_BIAS) + fprintf(stderr, "bug: read_unlock\n"); +#endif + + rwlock->count--; + __spin_unlock(&rwlock->lock); +} + +/* TDB SPECIFIC */ + +/* lock a list in the database. list -1 is the alloc list */ +int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) +{ + tdb_rwlock_t *rwlocks; + + if (!tdb->map_ptr) return -1; + rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks); + + switch(rw_type) { + case F_RDLCK: + __read_lock(&rwlocks[list+1]); + break; + + case F_WRLCK: + __write_lock(&rwlocks[list+1]); + break; + + default: + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + return 0; +} + +/* unlock the database. */ +int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) +{ + tdb_rwlock_t *rwlocks; + + if (!tdb->map_ptr) return -1; + rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks); + + switch(rw_type) { + case F_RDLCK: + __read_unlock(&rwlocks[list+1]); + break; + + case F_WRLCK: + __write_unlock(&rwlocks[list+1]); + break; + + default: + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + return 0; +} + +int tdb_create_rwlocks(int fd, unsigned int hash_size) +{ + unsigned size, i; + tdb_rwlock_t *rwlocks; + + size = (hash_size + 1) * sizeof(tdb_rwlock_t); + rwlocks = malloc(size); + if (!rwlocks) + return -1; + + for(i = 0; i < hash_size+1; i++) { + __spin_lock_init(&rwlocks[i].lock); + rwlocks[i].count = 0; + } + + /* Write it out (appending to end) */ + if (write(fd, rwlocks, size) != size) { + free(rwlocks); + return -1; + } + smp_machine = this_is_smp(); + free(rwlocks); + return 0; +} + +int tdb_clear_spinlocks(TDB_CONTEXT *tdb) +{ + tdb_rwlock_t *rwlocks; + unsigned i; + + if (tdb->header.rwlocks == 0) return 0; + if (!tdb->map_ptr) return -1; + + /* We're mmapped here */ + rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks); + for(i = 0; i < tdb->header.hash_size+1; i++) { + __spin_lock_init(&rwlocks[i].lock); + rwlocks[i].count = 0; + } + return 0; +} +#else +int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; } +int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; } +int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; } + +/* Non-spinlock version: remove spinlock pointer */ +int tdb_clear_spinlocks(TDB_CONTEXT *tdb) +{ + tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks + - (char *)&tdb->header); + + tdb->header.rwlocks = 0; + if (lseek(tdb->fd, off, SEEK_SET) != off + || write(tdb->fd, (void *)&tdb->header.rwlocks, + sizeof(tdb->header.rwlocks)) + != sizeof(tdb->header.rwlocks)) + return -1; + return 0; +} +#endif |