Initial import

1 files changed, 168 insertions, 0 deletions

diff --git a/lib/atomic64.c b/lib/atomic64.c
new file mode 100644
index 000000000..1298c05ef
--- /dev/null
+++ b/lib/atomic64.c
@@ -0,0 +1,168 @@
+/*
+ * Generic implementation of 64-bit atomics using spinlocks,
+ * useful on processors that don't have 64-bit atomic instructions.
+ *
+ * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/types.h>
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/atomic.h>
+
+/*
+ * We use a hashed array of spinlocks to provide exclusive access
+ * to each atomic64_t variable.  Since this is expected to used on
+ * systems with small numbers of CPUs (<= 4 or so), we use a
+ * relatively small array of 16 spinlocks to avoid wasting too much
+ * memory on the spinlock array.
+ */
+#define NR_LOCKS	16
+
+/*
+ * Ensure each lock is in a separate cacheline.
+ */
+static union {
+	raw_spinlock_t lock;
+	char pad[L1_CACHE_BYTES];
+} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
+	[0 ... (NR_LOCKS - 1)] = {
+		.lock =  __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
+	},
+};
+
+static inline raw_spinlock_t *lock_addr(const atomic64_t *v)
+{
+	unsigned long addr = (unsigned long) v;
+
+	addr >>= L1_CACHE_SHIFT;
+	addr ^= (addr >> 8) ^ (addr >> 16);
+	return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;
+}
+
+long long atomic64_read(const atomic64_t *v)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+	long long val;
+
+	raw_spin_lock_irqsave(lock, flags);
+	val = v->counter;
+	raw_spin_unlock_irqrestore(lock, flags);
+	return val;
+}
+EXPORT_SYMBOL(atomic64_read);
+
+void atomic64_set(atomic64_t *v, long long i)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+
+	raw_spin_lock_irqsave(lock, flags);
+	v->counter = i;
+	raw_spin_unlock_irqrestore(lock, flags);
+}
+EXPORT_SYMBOL(atomic64_set);
+
+#define ATOMIC64_OP(op, c_op)						\
+void atomic64_##op(long long a, atomic64_t *v)				\
+{									\
+	unsigned long flags;						\
+	raw_spinlock_t *lock = lock_addr(v);				\
+									\
+	raw_spin_lock_irqsave(lock, flags);				\
+	v->counter c_op a;						\
+	raw_spin_unlock_irqrestore(lock, flags);			\
+}									\
+EXPORT_SYMBOL(atomic64_##op);
+
+#define ATOMIC64_OP_RETURN(op, c_op)					\
+long long atomic64_##op##_return(long long a, atomic64_t *v)		\
+{									\
+	unsigned long flags;						\
+	raw_spinlock_t *lock = lock_addr(v);				\
+	long long val;							\
+									\
+	raw_spin_lock_irqsave(lock, flags);				\
+	val = (v->counter c_op a);					\
+	raw_spin_unlock_irqrestore(lock, flags);			\
+	return val;							\
+}									\
+EXPORT_SYMBOL(atomic64_##op##_return);
+
+#define ATOMIC64_OPS(op, c_op)						\
+	ATOMIC64_OP(op, c_op)						\
+	ATOMIC64_OP_RETURN(op, c_op)
+
+ATOMIC64_OPS(add, +=)
+ATOMIC64_OPS(sub, -=)
+
+#undef ATOMIC64_OPS
+#undef ATOMIC64_OP_RETURN
+#undef ATOMIC64_OP
+
+long long atomic64_dec_if_positive(atomic64_t *v)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+	long long val;
+
+	raw_spin_lock_irqsave(lock, flags);
+	val = v->counter - 1;
+	if (val >= 0)
+		v->counter = val;
+	raw_spin_unlock_irqrestore(lock, flags);
+	return val;
+}
+EXPORT_SYMBOL(atomic64_dec_if_positive);
+
+long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+	long long val;
+
+	raw_spin_lock_irqsave(lock, flags);
+	val = v->counter;
+	if (val == o)
+		v->counter = n;
+	raw_spin_unlock_irqrestore(lock, flags);
+	return val;
+}
+EXPORT_SYMBOL(atomic64_cmpxchg);
+
+long long atomic64_xchg(atomic64_t *v, long long new)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+	long long val;
+
+	raw_spin_lock_irqsave(lock, flags);
+	val = v->counter;
+	v->counter = new;
+	raw_spin_unlock_irqrestore(lock, flags);
+	return val;
+}
+EXPORT_SYMBOL(atomic64_xchg);
+
+int atomic64_add_unless(atomic64_t *v, long long a, long long u)
+{
+	unsigned long flags;
+	raw_spinlock_t *lock = lock_addr(v);
+	int ret = 0;
+
+	raw_spin_lock_irqsave(lock, flags);
+	if (v->counter != u) {
+		v->counter += a;
+		ret = 1;
+	}
+	raw_spin_unlock_irqrestore(lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(atomic64_add_unless);