[RFC][PATCH 4/7] x86: Add atomic_test_and_set_bit()

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-atomic_set_and_test_bit.patch --]
[-- Type: text/plain, Size: 817 bytes --]

For use in qspinlock because unconditional atomic ops scale better
than cmpxchg loops.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
 arch/x86/include/asm/atomic.h |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -218,6 +218,19 @@ static inline short int atomic_inc_short
 	return *v;
 }
 
+/**
+ * test_and_set_bit - Set a bit and return its old value
+ * @nr: Bit to set
+ * @addr: Address to count from
+ *
+ * This operation is atomic and cannot be reordered.
+ * It also implies a memory barrier.
+ */
+static inline int atomic_test_and_set_bit(int nr, atomic_t *v)
+{
+	GEN_BINARY_RMWcc(LOCK_PREFIX "bts", v->counter, "Ir", nr, "%0", "c");
+}
+
 #ifdef CONFIG_X86_64
 /**
  * atomic_or_long - OR of two long integers