Compiler implementations may provide sub-optimal support for
a memory_order passed in as a run-time value
(ref. https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html).
Document that OVS atomics require the memory order to be passed in as
a compile-time constant, and modify lib/cmap.c to comply with this.
Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
---
lib/cmap.c | 18 +++++++++++-------
lib/ovs-atomic.h | 3 +++
2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/lib/cmap.c b/lib/cmap.c
index ba744cc..60629b1 100644
--- a/lib/cmap.c
+++ b/lib/cmap.c
@@ -163,19 +163,23 @@ struct cmap_impl {
};
BUILD_ASSERT_DECL(sizeof(struct cmap_impl) == CACHE_LINE_SIZE);
-static uint32_t cmap_get_hash__(const atomic_uint32_t *hash,
- memory_order order)
+static inline uint32_t cmap_get_hash(const atomic_uint32_t *hash)
{
uint32_t hash__;
- atomic_read_explicit(CONST_CAST(ATOMIC(uint32_t) *, hash), &hash__, order);
+ atomic_read_explicit(CONST_CAST(ATOMIC(uint32_t) *, hash), &hash__,
+ memory_order_acquire);
return hash__;
}
-#define cmap_get_hash(HASH) \
- cmap_get_hash__(HASH, memory_order_acquire)
-#define cmap_get_hash_protected(HASH) \
- cmap_get_hash__(HASH, memory_order_relaxed)
+static inline uint32_t cmap_get_hash_protected(const atomic_uint32_t *hash)
+{
+ uint32_t hash__;
+
+ atomic_read_explicit(CONST_CAST(ATOMIC(uint32_t) *, hash), &hash__,
+ memory_order_relaxed);
+ return hash__;
+}
static struct cmap_impl *cmap_rehash(struct cmap *, uint32_t mask);
diff --git a/lib/ovs-atomic.h b/lib/ovs-atomic.h
index a76fe14..2633e5e 100644
--- a/lib/ovs-atomic.h
+++ b/lib/ovs-atomic.h
@@ -175,6 +175,9 @@
* whole system, providing a total order for stores an all atomic
* variables.
*
+ * OVS atomics require the memory_order to be passed as a compile-time constant
+ * value.
+ *
* The following functions insert explicit barriers. Most of the other atomic
* functions also include barriers.
*
--
1.7.10.4
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