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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
commit84adefa331c4159d432d22840663c38f155cd4c1 (patch)
treebff9a9c66adda4df2106dfd0e5c053ab182a12bd /erts/include/internal/ppc32/rwlock.h
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The R13B03 release.OTP_R13B03
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-rw-r--r--erts/include/internal/ppc32/rwlock.h153
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diff --git a/erts/include/internal/ppc32/rwlock.h b/erts/include/internal/ppc32/rwlock.h
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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 */