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-rw-r--r--tdb/spinlock.c430
1 files changed, 430 insertions, 0 deletions
diff --git a/tdb/spinlock.c b/tdb/spinlock.c
new file mode 100644
index 0000000000..2370ce3bdd
--- /dev/null
+++ b/tdb/spinlock.c
@@ -0,0 +1,430 @@
+/*
+ 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 <signal.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
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