The R13B03 release.OTP_R13B03

1 files changed, 92 insertions, 0 deletions

diff --git a/erts/include/internal/i386/spinlock.h b/erts/include/internal/i386/spinlock.h
new file mode 100644
index 0000000000..2b4832e26a
--- /dev/null
+++ b/erts/include/internal/i386/spinlock.h
@@ -0,0 +1,92 @@
+/*
+ * %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 spinlocks on x86/x86-64.
+ * Author: Mikael Pettersson.
+ */
+#ifndef ETHREAD_I386_SPINLOCK_H
+#define ETHREAD_I386_SPINLOCK_H
+
+/* A spinlock is the low byte of an aligned 32-bit integer.
+ * A non-zero value means that the lock is locked.
+ */
+typedef struct {
+    volatile unsigned int lock;
+} ethr_native_spinlock_t;
+
+#ifdef ETHR_TRY_INLINE_FUNCS
+
+static ETHR_INLINE void
+ethr_native_spinlock_init(ethr_native_spinlock_t *lock)
+{
+    lock->lock = 0;
+}
+
+static ETHR_INLINE void
+ethr_native_spin_unlock(ethr_native_spinlock_t *lock)
+{
+    /* To unlock we move 0 to the lock.
+     * On i386 this needs to be a locked operation
+     * to avoid Pentium Pro errata 66 and 92.
+     */
+#if defined(__x86_64__)
+    __asm__ __volatile__("" : : : "memory");
+    *(unsigned char*)&lock->lock = 0;
+#else
+    char tmp = 0;
+    __asm__ __volatile__(
+	"xchgb %b0, %1"
+	: "=q"(tmp), "=m"(lock->lock)
+	: "0"(tmp) : "memory");
+#endif
+}
+
+static ETHR_INLINE int
+ethr_native_spin_trylock(ethr_native_spinlock_t *lock)
+{
+    char tmp = 1;
+    __asm__ __volatile__(
+	"xchgb %b0, %1"
+	: "=q"(tmp), "=m"(lock->lock)
+	: "0"(tmp) : "memory");
+    return tmp == 0;
+}
+
+static ETHR_INLINE int
+ethr_native_spin_is_locked(ethr_native_spinlock_t *lock)
+{
+    return *(volatile unsigned char*)&lock->lock != 0;
+}
+
+static ETHR_INLINE void
+ethr_native_spin_lock(ethr_native_spinlock_t *lock)
+{
+    for(;;) {
+	if (__builtin_expect(ethr_native_spin_trylock(lock) != 0, 1))
+	    break;
+	do {
+	    __asm__ __volatile__("rep;nop" : "=m"(lock->lock) : : "memory");
+	} while (ethr_native_spin_is_locked(lock));
+    }
+}
+
+#endif /* ETHR_TRY_INLINE_FUNCS */
+
+#endif /* ETHREAD_I386_SPINLOCK_H */