Hi Qiaobin, This patch: http://patchwork.dpdk.org/patch/46105/ covers the bug. Honnappa suggested a fix that would work well for the lock free implementation as well.
>-----Original Message----- >From: Qiaobin Fu [mailto:[email protected]] >Sent: Tuesday, October 9, 2018 12:29 PM >To: Richardson, Bruce <[email protected]>; De Lara Guarch, Pablo ><[email protected]> >Cc: [email protected]; [email protected]; Wiles, Keith <[email protected]>; >Gobriel, Sameh <[email protected]>; Tai, Charlie ><[email protected]>; [email protected]; [email protected]; >[email protected]; Wang, Yipeng1 ><[email protected]>; [email protected]; [email protected] >Subject: [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate() > >In current implementation of rte_hash_iterate(), it >tries to obtain the lock after the while loop. However, >this may lead to a bug. Notice the following racing condition: > >1. The while loop above finishes because it finds > a not empty slot. But it does so without a lock. >2. Then we get the lock. >3. The position that was once not empty is now empty. > BUG because next_key is invalid. > >This patch fixes this small bug. > >Signed-off-by: Qiaobin Fu <[email protected]> >Reviewed-by: Michel Machado <[email protected]> >--- > lib/librte_hash/rte_cuckoo_hash.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > >diff --git a/lib/librte_hash/rte_cuckoo_hash.c >b/lib/librte_hash/rte_cuckoo_hash.c >index f7b86c8c9..a3e76684d 100644 >--- a/lib/librte_hash/rte_cuckoo_hash.c >+++ b/lib/librte_hash/rte_cuckoo_hash.c >@@ -1317,16 +1317,18 @@ rte_hash_iterate(const struct rte_hash *h, const void >**key, void **data, uint32 > bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES; > idx = *next % RTE_HASH_BUCKET_ENTRIES; > >+ __hash_rw_reader_lock(h); > /* If current position is empty, go to the next one */ > while (h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) { > (*next)++; > /* End of table */ >- if (*next == total_entries) >+ if (*next == total_entries) { >+ __hash_rw_reader_unlock(h); > return -ENOENT; >+ } > bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES; > idx = *next % RTE_HASH_BUCKET_ENTRIES; > } >- __hash_rw_reader_lock(h); > /* Get position of entry in key table */ > position = h->buckets[bucket_idx].key_idx[idx]; > next_key = (struct rte_hash_key *) ((char *)h->key_store + >-- >2.17.1
