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| author |   Herbert Xu <herbert@gondor.apana.org.au> | 2015-03-12 22:07:49 +1100 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2015-03-12 23:02:30 -0400 |
| commit | 9497df88ab5567daa001829051c5f87161a81ff0 (patch) | |
| tree | 4631c01eb33d6f8bbcf018f47d31d19ad4fac5a4 /lib | |
| parent | Merge branch 'listener_refactor' (diff) | |
| download | linux-dev-9497df88ab5567daa001829051c5f87161a81ff0.tar.xz linux-dev-9497df88ab5567daa001829051c5f87161a81ff0.zip | |
rhashtable: Fix reader/rehash race
There is a potential race condition between readers and the rehasher.
In particular, the rehasher could have started a rehash while the
reader finishes a scan of the old table but fails to see the new
table pointer.
This patch closes this window by adding smp_wmb/smp_rmb.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/rhashtable.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 6ffc793145f3..68210cc2bab8 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -271,6 +271,9 @@ static void rhashtable_rehash(struct rhashtable *ht, */ rcu_assign_pointer(ht->future_tbl, new_tbl); + /* Ensure the new table is visible to readers. */ + smp_wmb(); + for (old_hash = 0; old_hash < old_tbl->size; old_hash++) rhashtable_rehash_chain(ht, old_hash); @@ -618,6 +621,9 @@ restart: return rht_obj(ht, he); } + /* Ensure we see any new tables. */ + smp_rmb(); + old_tbl = tbl; tbl = rht_dereference_rcu(ht->future_tbl, ht); if (unlikely(tbl != old_tbl)) |