| Message ID | 20151208090904.GA17605@gondor.apana.org.au |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On 12/08/15 at 05:09pm, Herbert Xu wrote: > The patch 9497df88ab5567daa001829051c5f87161a81ff0 ("rhashtable: > Fix reader/rehash race") added a pair of barriers. In fact the > wmb is superfluous because every subsequent write to the old or > new hash table uses rcu_assign_pointer, which itself carriers a > full barrier prior to the assignment. > > Therefore we may remove the explicit wmb. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> The RELEASE which is now in place afterwards act as a wmb as well, we are well protected ;-) Acked-by: Thomas Graf <tgraf@suug.ch> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Herbert Xu <herbert@gondor.apana.org.au> Date: Tue, 8 Dec 2015 17:09:04 +0800 > The patch 9497df88ab5567daa001829051c5f87161a81ff0 ("rhashtable: > Fix reader/rehash race") added a pair of barriers. In fact the > wmb is superfluous because every subsequent write to the old or > new hash table uses rcu_assign_pointer, which itself carriers a > full barrier prior to the assignment. > > Therefore we may remove the explicit wmb. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Applied to net-next. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 1c624db..d1f94b4 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -232,9 +232,6 @@ static int rhashtable_rehash_attach(struct rhashtable *ht, */ rcu_assign_pointer(old_tbl->future_tbl, new_tbl); - /* Ensure the new table is visible to readers. */ - smp_wmb(); - spin_unlock_bh(old_tbl->locks); return 0;
The patch 9497df88ab5567daa001829051c5f87161a81ff0 ("rhashtable: Fix reader/rehash race") added a pair of barriers. In fact the wmb is superfluous because every subsequent write to the old or new hash table uses rcu_assign_pointer, which itself carriers a full barrier prior to the assignment. Therefore we may remove the explicit wmb. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>