[dpdk-stable] [PATCH 1/2] hash: fix unlimited cuckoo path

[Yuanhan Liu]

Both are applied to dpdk stable branch 16.07.

Thanks.

	--yliu

On Wed, Nov 09, 2016 at 05:22:03PM +0000, Pablo de Lara wrote:
> When trying to insert a new entry, if its target bucket is full,
> the alternative location (bucket) of one of the entries is checked,
> to try to find an empty slot, with make_space_bucket.
> This function is called every time a new bucket is checked, recursively.
> To avoid having a very long insert operation (and to avoid filling up
> the stack), a limit in the number of pushes is introduced.
> 
> Fixes: 48a399119619 ("hash: replace with cuckoo hash implementation")
> 
> Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
> ---
>  lib/librte_hash/rte_cuckoo_hash.c | 6 +++++-
>  lib/librte_hash/rte_cuckoo_hash.h | 2 ++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
> index 26e54f6..53363ed 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.c
> +++ b/lib/librte_hash/rte_cuckoo_hash.c
> @@ -408,6 +408,7 @@ rte_hash_reset(struct rte_hash *h)
>  static inline int
>  make_space_bucket(const struct rte_hash *h, struct rte_hash_bucket *bkt)
>  {
> +	static unsigned int nr_pushes;
>  	unsigned i, j;
>  	int ret;
>  	uint32_t next_bucket_idx;
> @@ -444,11 +445,13 @@ make_space_bucket(const struct rte_hash *h, struct rte_hash_bucket *bkt)
>  			break;
>  
>  	/* All entries have been pushed, so entry cannot be added */
> -	if (i == RTE_HASH_BUCKET_ENTRIES)
> +	if (i == RTE_HASH_BUCKET_ENTRIES || nr_pushes > RTE_HASH_MAX_PUSHES)
>  		return -ENOSPC;
>  
>  	/* Set flag to indicate that this entry is going to be pushed */
>  	bkt->flag[i] = 1;
> +
> +	nr_pushes++;
>  	/* Need room in alternative bucket to insert the pushed entry */
>  	ret = make_space_bucket(h, next_bkt[i]);
>  	/*
> @@ -458,6 +461,7 @@ make_space_bucket(const struct rte_hash *h, struct rte_hash_bucket *bkt)
>  	 * or return error
>  	 */
>  	bkt->flag[i] = 0;
> +	nr_pushes = 0;
>  	if (ret >= 0) {
>  		next_bkt[i]->signatures[ret].alt = bkt->signatures[i].current;
>  		next_bkt[i]->signatures[ret].current = bkt->signatures[i].alt;
> diff --git a/lib/librte_hash/rte_cuckoo_hash.h b/lib/librte_hash/rte_cuckoo_hash.h
> index 6c76700..9625fff 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.h
> +++ b/lib/librte_hash/rte_cuckoo_hash.h
> @@ -138,6 +138,8 @@ enum add_key_case {
>  
>  #define LCORE_CACHE_SIZE		64
>  
> +#define RTE_HASH_MAX_PUSHES             100
> +
>  #define RTE_HASH_BFS_QUEUE_MAX_LEN       1000
>  
>  #define RTE_XABORT_CUCKOO_PATH_INVALIDED 0x4
> -- 
> 2.7.4