[PATCH v3 1/7] eal: generic 64 bit counter

[Stephen Hemminger <stephen@networkplumber.org>]

This header implements 64 bit counters that are NOT atomic
but are safe against load/store splits on 32 bit platforms.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
---
 lib/eal/include/meson.build   |  1 +
 lib/eal/include/rte_counter.h | 91 +++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 lib/eal/include/rte_counter.h

diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build
index e94b056d46..c070dd0079 100644
--- a/lib/eal/include/meson.build
+++ b/lib/eal/include/meson.build
@@ -12,6 +12,7 @@ headers += files(
         'rte_class.h',
         'rte_common.h',
         'rte_compat.h',
+        'rte_counter.h',
         'rte_debug.h',
         'rte_dev.h',
         'rte_devargs.h',
diff --git a/lib/eal/include/rte_counter.h b/lib/eal/include/rte_counter.h
new file mode 100644
index 0000000000..8068d6d26e
--- /dev/null
+++ b/lib/eal/include/rte_counter.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) Stephen Hemminger <stephen@networkplumber.org>
+ */
+
+#ifndef _RTE_COUNTER_H_
+#define _RTE_COUNTER_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file
+ * RTE Counter
+ *
+ * A counter is 64 bit value that is safe from split read/write
+ * on 32 bit platforms. It assumes that only one cpu at a time
+ * will update the counter, and another CPU may want to read it.
+ *
+ * This is a much weaker guarantee than full atomic variables
+ * but is faster since no locked operations are required for update.
+ */
+
+#include <stdatomic.h>
+
+#ifdef RTE_ARCH_64
+/*
+ * On a platform that can support native 64 bit type, no special handling.
+ * These are just wrapper around 64 bit value.
+ */
+typedef uint64_t rte_counter64_t;
+
+/**
+ * Add value to counter.
+ */
+__rte_experimental
+static inline void
+rte_counter64_add(rte_counter64_t *counter, uint32_t val)
+{
+	*counter += val;
+}
+
+__rte_experimental
+static inline uint64_t
+rte_counter64_fetch(const rte_counter64_t *counter)
+{
+	return *counter;
+}
+
+__rte_experimental
+static inline void
+rte_counter64_reset(rte_counter64_t *counter)
+{
+	*counter = 0;
+}
+
+#else
+/*
+ * On a 32 bit platform need to use atomic to force the compler to not
+ * split 64 bit read/write.
+ */
+typedef RTE_ATOMIC(uint64_t) rte_counter64_t;
+
+__rte_experimental
+static inline void
+rte_counter64_add(rte_counter64_t *counter, uint32_t val)
+{
+	rte_atomic_fetch_add_explicit(counter, val, rte_memory_order_relaxed);
+}
+
+__rte_experimental
+static inline uint64_t
+rte_counter64_fetch(const rte_counter64_t *counter)
+{
+	return rte_atomic_load_explicit(counter, rte_memory_order_relaxed);
+}
+
+__rte_experimental
+static inline void
+rte_counter64_reset(rte_counter64_t *counter)
+{
+	rte_atomic_store_explicit(counter, 0, rte_memory_order_relaxed);
+}
+#endif
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_COUNTER_H_ */
-- 
2.43.0