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Diffstat (limited to 'erts/include/internal/ppc32/rwlock.h')
| -rw-r--r-- | erts/include/internal/ppc32/rwlock.h | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/erts/include/internal/ppc32/rwlock.h b/erts/include/internal/ppc32/rwlock.h new file mode 100644 index 0000000000..9bdab12826 --- /dev/null +++ b/erts/include/internal/ppc32/rwlock.h @@ -0,0 +1,153 @@ +/* + * %CopyrightBegin% + * + * Copyright Ericsson AB 2005-2009. All Rights Reserved. + * + * The contents of this file are subject to the Erlang Public License, + * Version 1.1, (the "License"); you may not use this file except in + * compliance with the License. You should have received a copy of the + * Erlang Public License along with this software. If not, it can be + * retrieved online at http://www.erlang.org/. + * + * Software distributed under the License is distributed on an "AS IS" + * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + * the License for the specific language governing rights and limitations + * under the License. + * + * %CopyrightEnd% + */ + +/* + * Native ethread rwlocks on PowerPC. + * Author: Mikael Pettersson. + * + * Based on the examples in Appendix E of Motorola's + * "Programming Environments Manual For 32-Bit Implementations + * of the PowerPC Architecture". Uses eieio instead of sync + * in the unlock sequence, as suggested in the manual. + */ +#ifndef ETHREAD_PPC_RWLOCK_H +#define ETHREAD_PPC_RWLOCK_H + +/* Unlocked if zero, read-locked if negative, write-locked if +1. */ +typedef struct { + volatile int lock; +} ethr_native_rwlock_t; + +#ifdef ETHR_TRY_INLINE_FUNCS + +static ETHR_INLINE void +ethr_native_rwlock_init(ethr_native_rwlock_t *lock) +{ + lock->lock = 0; +} + +static ETHR_INLINE void +ethr_native_read_unlock(ethr_native_rwlock_t *lock) +{ + int tmp; + + /* this is eieio + ethr_native_atomic_inc() - isync */ + __asm__ __volatile__( + "eieio\n\t" + "1:\t" + "lwarx %0,0,%1\n\t" + "addic %0,%0,1\n\t" + "stwcx. %0,0,%1\n\t" + "bne- 1b" + : "=&r"(tmp) + : "r"(&lock->lock) + : "cr0", "memory"); +} + +static ETHR_INLINE int +ethr_native_read_trylock(ethr_native_rwlock_t *lock) +{ + int counter; + + __asm__ __volatile__( + "1:\t" + "lwarx %0,0,%1\n\t" /* read lock to counter */ + "addic. %0,%0,-1\n\t" /* decrement counter */ + "bge- 2f\n\t" /* bail if >= 0 (write-locked) */ + "stwcx. %0,0,%1\n\t" /* try to store decremented counter */ + "bne- 1b\n\t" /* loop if lost reservation */ + "isync\n\t" /* wait for previous insns to complete */ + "2:" + : "=&r"(counter) + : "r"(&lock->lock) + : "cr0", "memory" +#if __GNUC__ > 2 + ,"xer" +#endif + ); + return counter < 0; +} + +static ETHR_INLINE int +ethr_native_read_is_locked(ethr_native_rwlock_t *lock) +{ + return lock->lock > 0; +} + +static ETHR_INLINE void +ethr_native_read_lock(ethr_native_rwlock_t *lock) +{ + for(;;) { + if (__builtin_expect(ethr_native_read_trylock(lock) != 0, 1)) + break; + do { + __asm__ __volatile__("":::"memory"); + } while (ethr_native_read_is_locked(lock)); + } +} + +static ETHR_INLINE void +ethr_native_write_unlock(ethr_native_rwlock_t *lock) +{ + __asm__ __volatile__("eieio" : : : "memory"); + lock->lock = 0; +} + +static ETHR_INLINE int +ethr_native_write_trylock(ethr_native_rwlock_t *lock) +{ + int prev; + + /* identical to ethr_native_spin_trylock() */ + __asm__ __volatile__( + "1:\t" + "lwarx %0,0,%1\n\t" /* read lock to prev */ + "cmpwi 0,%0,0\n\t" + "bne- 2f\n\t" /* bail if non-zero (any lock) */ + "stwcx. %2,0,%1\n\t" /* try to make the lock positive */ + "bne- 1b\n\t" /* loop if lost reservation */ + "isync\n\t" /* wait for previous insns to complete */ + "2:" + : "=&r"(prev) + : "r"(&lock->lock), "r"(1) + : "cr0", "memory"); + return prev == 0; +} + +static ETHR_INLINE int +ethr_native_write_is_locked(ethr_native_rwlock_t *lock) +{ + return lock->lock != 0; +} + +static ETHR_INLINE void +ethr_native_write_lock(ethr_native_rwlock_t *lock) +{ + for(;;) { + if (__builtin_expect(ethr_native_write_trylock(lock) != 0, 1)) + break; + do { + __asm__ __volatile__("":::"memory"); + } while (ethr_native_write_is_locked(lock)); + } +} + +#endif /* ETHR_TRY_INLINE_FUNCS */ + +#endif /* ETHREAD_PPC_RWLOCK_H */ |