[dpdk-dev] [PATCH v5 01/15] eal: introduce atomic exchange operation

[Stephen Hemminger <stephen@networkplumber.org>]

To handle atomic update of link status (64 bit), every driver
was doing its own version using cmpset.
Atomic exchange is a useful primitive in its own right;
therefore make it a EAL routine.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 .../common/include/arch/x86/rte_atomic.h           | 24 +++++++
 .../common/include/arch/x86/rte_atomic_32.h        | 12 ++++
 .../common/include/arch/x86/rte_atomic_64.h        | 12 ++++
 lib/librte_eal/common/include/generic/rte_atomic.h | 78 ++++++++++++++++++++++
 4 files changed, 126 insertions(+)

diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic.h b/lib/librte_eal/common/include/arch/x86/rte_atomic.h
index 8469f97e193a..20d10cc18e4e 100644
--- a/lib/librte_eal/common/include/arch/x86/rte_atomic.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic.h
@@ -59,6 +59,18 @@ rte_atomic16_cmpset(volatile uint16_t *dst, uint16_t exp, uint16_t src)
 	return res;
 }
 
+static inline uint16_t
+rte_atomic16_exchange(volatile uint16_t *dst, uint16_t val)
+{
+	asm volatile(
+			MPLOCKED
+			"xchgw %0, %1;"
+			: "=r" (val), "=m" (*dst)
+			: "0" (val),  "m" (*dst)
+			: "memory");         /* no-clobber list */
+	return val;
+}
+
 static inline int rte_atomic16_test_and_set(rte_atomic16_t *v)
 {
 	return rte_atomic16_cmpset((volatile uint16_t *)&v->cnt, 0, 1);
@@ -133,6 +145,18 @@ rte_atomic32_cmpset(volatile uint32_t *dst, uint32_t exp, uint32_t src)
 	return res;
 }
 
+static inline uint32_t
+rte_atomic32_exchange(volatile uint32_t *dst, uint32_t val)
+{
+	asm volatile(
+			MPLOCKED
+			"xchgl %0, %1;"
+			: "=r" (val), "=m" (*dst)
+			: "0" (val),  "m" (*dst)
+			: "memory");         /* no-clobber list */
+	return val;
+}
+
 static inline int rte_atomic32_test_and_set(rte_atomic32_t *v)
 {
 	return rte_atomic32_cmpset((volatile uint32_t *)&v->cnt, 0, 1);
diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic_32.h b/lib/librte_eal/common/include/arch/x86/rte_atomic_32.h
index fb3abf187998..43fa59355ac5 100644
--- a/lib/librte_eal/common/include/arch/x86/rte_atomic_32.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_32.h
@@ -98,6 +98,18 @@ rte_atomic64_cmpset(volatile uint64_t *dst, uint64_t exp, uint64_t src)
 	return res;
 }
 
+static inline uint64_t
+rte_atomic64_exchange(volatile uint64_t *dest, uint64_t val)
+{
+	uint64_t old;
+
+	do {
+		old = *dest;
+	} while (rte_atomic64_t_cmpset(dest, old, val));
+
+	return old;
+}
+
 static inline void
 rte_atomic64_init(rte_atomic64_t *v)
 {
diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
index 1a53a766bd72..fd2ec9c53796 100644
--- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
@@ -71,6 +71,18 @@ rte_atomic64_cmpset(volatile uint64_t *dst, uint64_t exp, uint64_t src)
 	return res;
 }
 
+static inline uint64_t
+rte_atomic64_exchange(volatile uint64_t *dst, uint64_t val)
+{
+	asm volatile(
+			MPLOCKED
+			"xchgq %0, %1;"
+			: "=r" (val), "=m" (*dst)
+			: "0" (val),  "m" (*dst)
+			: "memory");         /* no-clobber list */
+	return val;
+}
+
 static inline void
 rte_atomic64_init(rte_atomic64_t *v)
 {
diff --git a/lib/librte_eal/common/include/generic/rte_atomic.h b/lib/librte_eal/common/include/generic/rte_atomic.h
index 3ba7245a3e17..d3348343c1fb 100644
--- a/lib/librte_eal/common/include/generic/rte_atomic.h
+++ b/lib/librte_eal/common/include/generic/rte_atomic.h
@@ -139,6 +139,32 @@ rte_atomic16_cmpset(volatile uint16_t *dst, uint16_t exp, uint16_t src)
 }
 #endif
 
+/**
+ * Atomic exchange.
+ *
+ * (atomic) equivalent to:
+ *   ret = *dst
+ *   *dst = val;
+ *   return ret;
+ *
+ * @param dst
+ *   The destination location into which the value will be written.
+ * @param val
+ *   The new value.
+ * @return
+ *   The original value at that location
+ */
+static inline uint16_t
+rte_atomic16_exchange(volatile uint16_t *dst, uint16_t val);
+
+#ifdef RTE_FORCE_INTRINSICS
+static inline uint16_t
+rte_atomic16_exchange(volatile uint16_t *dst, uint16_t val)
+{
+	return __atomic_exchange_2(dst, val, __ATOMIC_SEQ_CST);
+}
+#endif
+
 /**
  * The atomic counter structure.
  */
@@ -392,6 +418,32 @@ rte_atomic32_cmpset(volatile uint32_t *dst, uint32_t exp, uint32_t src)
 }
 #endif
 
+/**
+ * Atomic exchange.
+ *
+ * (atomic) equivalent to:
+ *   ret = *dst
+ *   *dst = val;
+ *   return ret;
+ *
+ * @param dst
+ *   The destination location into which the value will be written.
+ * @param val
+ *   The new value.
+ * @return
+ *   The original value at that location
+ */
+static inline uint32_t
+rte_atomic32_exchange(volatile uint32_t *dst, uint32_t val);
+
+#ifdef RTE_FORCE_INTRINSICS
+static inline uint32_t
+rte_atomic32_exchange(volatile uint32_t *dst, uint32_t val)
+{
+	return __atomic_exchange_4(dst, val, __ATOMIC_SEQ_CST);
+}
+#endif
+
 /**
  * The atomic counter structure.
  */
@@ -644,6 +696,32 @@ rte_atomic64_cmpset(volatile uint64_t *dst, uint64_t exp, uint64_t src)
 }
 #endif
 
+/**
+ * Atomic exchange.
+ *
+ * (atomic) equivalent to:
+ *   ret = *dst
+ *   *dst = val;
+ *   return ret;
+ *
+ * @param dst
+ *   The destination location into which the value will be written.
+ * @param val
+ *   The new value.
+ * @return
+ *   The original value at that location
+ */
+static inline uint64_t
+rte_atomic64_exchange(volatile uint64_t *dst, uint64_t val);
+
+#ifdef RTE_FORCE_INTRINSICS
+static inline uint64_t
+rte_atomic64_exchange(volatile uint64_t *dst, uint64_t val)
+{
+	return __atomic_exchange_4(dst, val, __ATOMIC_SEQ_CST);
+}
+#endif
+
 /**
  * The atomic counter structure.
  */
-- 
2.15.1