Since this is not a DMA barrier we do not want to use wmb() here.
Replace it with a weak atomic fence.
For x86-64 this has no change to the assembly output.
Signed-off-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
---
providers/mlx5/mlx5.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/providers/mlx5/mlx5.h b/providers/mlx5/mlx5.h
index be52a0a75dded0..e63164c2caea7b 100644
--- a/providers/mlx5/mlx5.h
+++ b/providers/mlx5/mlx5.h
@@ -35,6 +35,7 @@
#include <stddef.h>
#include <stdio.h>
+#include <stdatomic.h>
#include <util/compiler.h>
#include <infiniband/driver.h>
@@ -683,7 +684,11 @@ static inline int mlx5_spin_lock(struct mlx5_spinlock *lock)
abort();
} else {
lock->in_use = 1;
- wmb();
+ /*
+ * This fence is not at all correct, but it increases the
+ * chance that in_use is detected by another thread without
+ * much runtime cost. */
+ atomic_thread_fence(memory_order_acq_rel);
}
return 0;
--
2.7.4
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