From 84adefa331c4159d432d22840663c38f155cd4c1 Mon Sep 17 00:00:00 2001
From: Erlang/OTP <otp@erlang.org>
Date: Fri, 20 Nov 2009 14:54:40 +0000
Subject: The R13B03 release.

---
 erts/include/internal/i386/rwlock.h | 134 ++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 erts/include/internal/i386/rwlock.h

(limited to 'erts/include/internal/i386/rwlock.h')

diff --git a/erts/include/internal/i386/rwlock.h b/erts/include/internal/i386/rwlock.h
new file mode 100644
index 0000000000..c009be8ef1
--- /dev/null
+++ b/erts/include/internal/i386/rwlock.h
@@ -0,0 +1,134 @@
+/*
+ * %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 x86/x86-64.
+ * Author: Mikael Pettersson.
+ *
+ * This code requires a 486 or newer processor.
+ */
+#ifndef ETHREAD_I386_RWLOCK_H
+#define ETHREAD_I386_RWLOCK_H
+
+/* XXX: describe the algorithm */
+typedef struct {
+    volatile int lock;
+} ethr_native_rwlock_t;
+
+#ifdef ETHR_TRY_INLINE_FUNCS
+
+#define ETHR_RWLOCK_OFFSET	(1<<24)
+
+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)
+{
+    __asm__ __volatile__(
+	"lock; decl %0"
+	: "=m"(lock->lock)
+	: "m"(lock->lock));
+}
+
+static ETHR_INLINE int
+ethr_native_read_trylock(ethr_native_rwlock_t *lock)
+{
+    int tmp;
+
+    tmp = 1;
+    __asm__ __volatile__(
+	"lock; xaddl %0, %1"
+	: "=r"(tmp)
+	: "m"(lock->lock), "0"(tmp));
+    /* tmp is now the lock's previous value */
+    if (__builtin_expect(tmp >= 0, 1))
+	return 1;
+    ethr_native_read_unlock(lock);
+    return 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__("rep;nop" : "=m"(lock->lock) : : "memory");
+	} while (ethr_native_read_is_locked(lock));
+    }
+}
+
+static ETHR_INLINE void
+ethr_native_write_unlock(ethr_native_rwlock_t *lock)
+{
+    __asm__ __volatile__(
+	"lock; addl %2,%0"
+	: "=m"(lock->lock)
+	: "m"(lock->lock), "i"(ETHR_RWLOCK_OFFSET));
+}
+
+static ETHR_INLINE int
+ethr_native_write_trylock(ethr_native_rwlock_t *lock)
+{
+    int tmp;
+
+    tmp = -ETHR_RWLOCK_OFFSET;
+    __asm__ __volatile__(
+	"lock; xaddl %0, %1"
+	: "=r"(tmp)
+	: "m"(lock->lock), "0"(tmp));
+    /* tmp is now the lock's previous value */
+    if (__builtin_expect(tmp == 0, 1))
+	return 1;
+    ethr_native_write_unlock(lock);
+    return 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__("rep;nop" : "=m"(lock->lock) : : "memory");
+	} while (ethr_native_write_is_locked(lock));
+    }
+}
+
+#endif /* ETHR_TRY_INLINE_FUNCS */
+
+#endif /* ETHREAD_I386_RWLOCK_H */
-- 
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