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/*
* %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 */
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