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-rw-r--r--Documentation/memory-barriers.txt14
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diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index eaabc3134294..ff07cd3b2f82 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1935,6 +1935,20 @@ There are some more advanced barrier functions:
relaxed I/O accessors and the Documentation/DMA-API.txt file for more
information on consistent memory.
+ (*) pmem_wmb();
+
+ This is for use with persistent memory to ensure that stores for which
+ modifications are written to persistent storage reached a platform
+ durability domain.
+
+ For example, after a non-temporal write to pmem region, we use pmem_wmb()
+ to ensure that stores have reached a platform durability domain. This ensures
+ that stores have updated persistent storage before any data access or
+ data transfer caused by subsequent instructions is initiated. This is
+ in addition to the ordering done by wmb().
+
+ For load from persistent memory, existing read memory barriers are sufficient
+ to ensure read ordering.
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IMPLICIT KERNEL MEMORY BARRIERS