From: NeilBrown <neilb@suse.com>
To: Thomas Graf <tgraf@suug.ch>,
Herbert Xu <herbert@gondor.apana.org.au>,
David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 6/7] rhashtable: use cmpxchg() to protect ->future_tbl.
Date: Mon, 18 Jun 2018 12:52:50 +1000 [thread overview]
Message-ID: <152929037051.23173.18373322147570571861.stgit@noble> (raw)
In-Reply-To: <152929034948.23173.8671757672560065344.stgit@noble>
Rather than borrowing one of the bucket locks to
protect ->future_tbl updates, use cmpxchg().
This gives more freedom to change how bucket locking
is implemented.
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NeilBrown <neilb@suse.com>
---
lib/rhashtable.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 2aa41c15df17..52ec83212856 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -297,21 +297,14 @@ static int rhashtable_rehash_attach(struct rhashtable *ht,
struct bucket_table *old_tbl,
struct bucket_table *new_tbl)
{
- /* Protect future_tbl using the first bucket lock. */
- spin_lock_bh(old_tbl->locks);
-
- /* Did somebody beat us to it? */
- if (rcu_access_pointer(old_tbl->future_tbl)) {
- spin_unlock_bh(old_tbl->locks);
- return -EEXIST;
- }
-
/* Make insertions go into the new, empty table right away. Deletions
* and lookups will be attempted in both tables until we synchronize.
+ * As cmpxchg() provides strong barriers, we do not need
+ * rcu_assign_pointer().
*/
- rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
- spin_unlock_bh(old_tbl->locks);
+ if (cmpxchg(&old_tbl->future_tbl, NULL, new_tbl) != NULL)
+ return -EEXIST;
return 0;
}
next prev parent reply other threads:[~2018-06-18 2:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-18 2:52 [PATCH 0/7] Assorted rhashtables cleanups NeilBrown
2018-06-18 2:52 ` [PATCH 5/7] rhashtable: simplify nested_table_alloc() and rht_bucket_nested_insert() NeilBrown
2018-06-18 2:52 ` NeilBrown [this message]
2018-06-18 2:52 ` [PATCH 3/7] rhashtable: remove nulls_base and related code NeilBrown
2018-06-18 2:52 ` [PATCH 2/7] rhashtable: split rhashtable.h NeilBrown
2018-06-18 2:52 ` [PATCH 7/7] rhashtable: clean up dereference of ->future_tbl NeilBrown
2018-06-18 2:52 ` [PATCH 4/7] rhashtable: simplify INIT_RHT_NULLS_HEAD() NeilBrown
2018-06-18 2:52 ` [PATCH 1/7] rhashtable: silence RCU warning in rhashtable_test NeilBrown
2018-06-22 4:43 ` [PATCH 0/7] Assorted rhashtables cleanups David Miller
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