[ovs-dev] [PATCH 15/19] datapath: Don't rcu_dereference() objects in table.

Jesse Gross jesse at nicira.com
Wed Dec 8 22:14:13 PST 2010


Each time that we modify the flow/port table, we reallocate the
array of pointers to objects in a particular bucket.  We then use
RCU to update the link to that bucket.  This means that we don't
need to use RCU to access the individual object pointers, since
they are constant for a given instance of the bucket data structure.
This doesn't cause a problem per se (though it does restrict the
optimizations that the compiler can perform and adds a memory barrier
on Alpha).  However, it is confusing and inconsistent since the
pointers are not protected by RCU and we don't use rcu_assign_pointer().

Found by sparse.

Signed-off-by: Jesse Gross <jesse at nicira.com>
---
 datapath/table.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/datapath/table.c b/datapath/table.c
index 86236e9..cfe7b2b 100644
--- a/datapath/table.c
+++ b/datapath/table.c
@@ -174,7 +174,7 @@ static int search_bucket(const struct tbl_bucket *bucket, void *target, u32 hash
 	int i;
 
 	for (i = 0; i < bucket->n_objs; i++) {
-		struct tbl_node *obj = rcu_dereference(bucket->objs[i]);
+		struct tbl_node *obj = bucket->objs[i];
 		if (obj->hash == hash && likely(cmp(obj, target)))
 			return i;
 	}
-- 
1.7.1





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