@@ -201,6 +201,147 @@ extern "C" {
uint32_t *: __rte_bit_assign32, \
uint64_t *: __rte_bit_assign64)(addr, nr, value)
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Generic selection macro to test exactly once the value of a bit in
+ * a 32-bit or 64-bit word. The type of operation depends on the type
+ * of the @c addr parameter.
+ *
+ * This function is guaranteed to result in exactly one memory load
+ * (e.g., it may not be eliminate or merged by the compiler).
+ *
+ * \code{.c}
+ * rte_bit_once_set(addr, 17);
+ * if (rte_bit_once_test(addr, 17)) {
+ * ...
+ * }
+ * \endcode
+ *
+ * In the above example, rte_bit_once_set() may not be removed by
+ * the compiler, which would be allowed in case rte_bit_set() and
+ * rte_bit_test() was used.
+ *
+ * \code{.c}
+ * while (rte_bit_once_test(addr, 17);
+ * ;
+ * \endcode
+ *
+ * In case rte_bit_test(addr, 17) was used instead, the resulting
+ * object code could (and in many cases would be) replaced with
+ * the equivalent to
+ * \code{.c}
+ * if (rte_bit_test(addr, 17)) {
+ * for (;;) // spin forever
+ * ;
+ * }
+ * \endcode
+ *
+ * rte_bit_once_test() does not give any guarantees in regards to
+ * memory ordering or atomicity.
+ *
+ * The regular bit set operations (e.g., rte_bit_test()) should be
+ * preferred over the "once" family of operations (e.g.,
+ * rte_bit_once_test()) if possible, since the latter may prevent
+ * optimizations crucial for run-time performance.
+ *
+ * @param addr
+ * A pointer to the word to query.
+ * @param nr
+ * The index of the bit.
+ * @return
+ * Returns true if the bit is set, and false otherwise.
+ */
+
+#define rte_bit_once_test(addr, nr) \
+ _Generic((addr), \
+ uint32_t *: __rte_bit_once_test32, \
+ uint64_t *: __rte_bit_once_test64)(addr, nr)
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Set bit in word exactly once.
+ *
+ * Set bit specified by @c nr in the word pointed to by @c addr to '1'
+ * exactly once.
+ *
+ * This function is guaranteed to result in exactly one memory load
+ * and exactly one memory store, *or* an atomic bit set operation.
+ *
+ * See rte_bit_test_once32() for more information and uses cases for
+ * the "once" class of functions.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ * A pointer to the word to modify.
+ * @param nr
+ * The index of the bit.
+ */
+#define rte_bit_once_set(addr, nr) \
+ _Generic((addr), \
+ uint32_t *: __rte_bit_once_set32, \
+ uint64_t *: __rte_bit_once_set64)(addr, nr)
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Clear bit in word exactly once.
+ *
+ * Set bit specified by @c nr in the word pointed to by @c addr to '0'
+ * exactly once.
+ *
+ * This function is guaranteed to result in exactly one memory load
+ * and exactly one memory store, *or* an atomic bit clear operation.
+ *
+ * See rte_bit_test_once32() for more information and uses cases for
+ * the "once" class of functions.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ * A pointer to the word to modify.
+ * @param nr
+ * The index of the bit.
+ */
+#define rte_bit_once_clear(addr, nr) \
+ _Generic((addr), \
+ uint32_t *: __rte_bit_once_clear32, \
+ uint64_t *: __rte_bit_once_clear64)(addr, nr)
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Assign a value to bit in a word exactly once.
+ *
+ * Set bit specified by @c nr in the word pointed to by @c addr to the
+ * value indicated by @c value exactly once.
+ *
+ * This function is guaranteed to result in exactly one memory load
+ * and exactly one memory store, *or* an atomic bit clear operation.
+ *
+ * This function does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ * A pointer to the word to modify.
+ * @param nr
+ * The index of the bit.
+ * @param value
+ * The new value of the bit - true for '1', or false for '0'.
+ */
+#define rte_bit_once_assign(addr, nr, value) \
+ _Generic((addr), \
+ uint32_t *: __rte_bit_once_assign32, \
+ uint64_t *: __rte_bit_once_assign64)(addr, nr, value)
+
#define __RTE_GEN_BIT_TEST(name, size, qualifier) \
static inline bool \
name(const qualifier uint ## size ## _t *addr, unsigned int nr) \
@@ -239,6 +380,14 @@ __RTE_GEN_BIT_TEST(__rte_bit_test64, 64,)
__RTE_GEN_BIT_SET(__rte_bit_set64, 64,)
__RTE_GEN_BIT_CLEAR(__rte_bit_clear64, 64,)
+__RTE_GEN_BIT_TEST(__rte_bit_once_test32, 32, volatile)
+__RTE_GEN_BIT_SET(__rte_bit_once_set32, 32, volatile)
+__RTE_GEN_BIT_CLEAR(__rte_bit_once_clear32, 32, volatile)
+
+__RTE_GEN_BIT_TEST(__rte_bit_once_test64, 64, volatile)
+__RTE_GEN_BIT_SET(__rte_bit_once_set64, 64, volatile)
+__RTE_GEN_BIT_CLEAR(__rte_bit_once_clear64, 64, volatile)
+
__rte_experimental
static inline void
__rte_bit_assign32(uint32_t *addr, unsigned int nr, bool value)
@@ -259,6 +408,27 @@ __rte_bit_assign64(uint64_t *addr, unsigned int nr, bool value)
__rte_bit_clear64(addr, nr);
}
+
+__rte_experimental
+static inline void
+__rte_bit_once_assign32(uint32_t *addr, unsigned int nr, bool value)
+{
+ if (value)
+ __rte_bit_once_set32(addr, nr);
+ else
+ __rte_bit_once_clear32(addr, nr);
+}
+
+__rte_experimental
+static inline void
+__rte_bit_once_assign64(volatile uint64_t *addr, unsigned int nr, bool value)
+{
+ if (value)
+ __rte_bit_once_set64(addr, nr);
+ else
+ __rte_bit_once_clear64(addr, nr);
+}
+
/*------------------------ 32-bit relaxed operations ------------------------*/
/**