diff options
| author | NeilBrown <neilb@suse.com> | 2018-06-18 12:52:50 +1000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-06-22 13:43:27 +0900 |
| commit | 0ad66449aa3cbaedbdeaf55bffce74084bb7e9f9 (patch) | |
| tree | 32b444b2154c26c3936446dcc9d1d234521f23a5 /lib/rhashtable.c | |
| parent | 5af68ef7333c8606bfe6e400cb962081518c3acb (diff) | |
rhashtable: use cmpxchg() to protect ->future_tbl.
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib/rhashtable.c')
| -rw-r--r-- | lib/rhashtable.c | 15 |
1 files 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; } |