[dpdk-dev] [PATCH] mempool: sort the rte_mempool_ops by name

[Jerin Jacob]

On Mon, Mar 2, 2020 at 7:27 AM <xiangxia.m.yue at gmail.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue at gmail.com>
>
> The order of mempool initiation affects mempool index in the
> rte_mempool_ops_table. For example, when building APPs with:
>
> $ gcc -lrte_mempool_bucket -lrte_mempool_ring ...
>
> The "bucket" mempool will be registered firstly, and its index
> in table is 0 while the index of "ring" mempool is 1. DPDK
> uses the mk/rte.app.mk to build APPs, and others, for example,
> Open vSwitch, use the libdpdk.a or libdpdk.so to build it.
> The mempool lib linked in dpdk and Open vSwitch is different.
>
> The mempool can be used between primary and secondary process,
> such as dpdk-pdump and pdump-pmd/Open vSwitch(pdump enabled).
> There will be a crash because dpdk-pdump creates the "ring_mp_mc"
> ring which index in table is 0, but the index of "bucket" ring
> is 0 in Open vSwitch. If Open vSwitch use the index 0 to get
> mempool ops and malloc memory from mempool. The crash will occur:
>
>     bucket_dequeue (access null and crash)
>     rte_mempool_get_ops (should get "ring_mp_mc",
>                          but get "bucket" mempool)
>     rte_mempool_ops_dequeue_bulk
>     ...
>     rte_pktmbuf_alloc
>     rte_pktmbuf_copy
>     pdump_copy
>     pdump_rx
>     rte_eth_rx_burst
>
> To avoid the crash, there are some solution:
> * constructor priority: Different mempool uses different
>   priority in RTE_INIT, but it's not easy to maintain.
>
> * change mk/rte.app.mk: Change the order in mk/rte.app.mk to
>   be same as libdpdk.a/libdpdk.so, but when adding a new mempool
>   driver in future, we must make sure the order.
>
> * register mempool orderly: Sort the mempool when registering,
>   so the lib linked will not affect the index in mempool table.
>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> ---
>  lib/librte_mempool/rte_mempool_ops.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool_ops.c b/lib/librte_mempool/rte_mempool_ops.c
> index 22c5251..06dfe16 100644
> --- a/lib/librte_mempool/rte_mempool_ops.c
> +++ b/lib/librte_mempool/rte_mempool_ops.c
> @@ -22,7 +22,7 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
>  rte_mempool_register_ops(const struct rte_mempool_ops *h)
>  {
>         struct rte_mempool_ops *ops;
> -       int16_t ops_index;
> +       unsigned ops_index, i;
>
>         rte_spinlock_lock(&rte_mempool_ops_table.sl);
>
> @@ -50,7 +50,19 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
>                 return -EEXIST;
>         }
>
> -       ops_index = rte_mempool_ops_table.num_ops++;
> +       /* sort the rte_mempool_ops by name. the order of the mempool
> +        * lib initiation will not affect rte_mempool_ops index. */

+1 for the fix.
For the implementation, why not use qsort_r() for sorting?


> +       ops_index = rte_mempool_ops_table.num_ops;
> +       for (i = 0; i < rte_mempool_ops_table.num_ops; i++) {
> +               if (strcmp(h->name, rte_mempool_ops_table.ops[i].name) < 0) {
> +                       do {
> +                               rte_mempool_ops_table.ops[ops_index] =
> +                                       rte_mempool_ops_table.ops[ops_index -1];
> +                       } while (--ops_index > i);
> +                       break;
> +               }
> +       }
> +
>         ops = &rte_mempool_ops_table.ops[ops_index];
>         strlcpy(ops->name, h->name, sizeof(ops->name));
>         ops->alloc = h->alloc;
> @@ -63,6 +75,8 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
>         ops->get_info = h->get_info;
>         ops->dequeue_contig_blocks = h->dequeue_contig_blocks;
>
> +       rte_mempool_ops_table.num_ops++;
> +
>         rte_spinlock_unlock(&rte_mempool_ops_table.sl);
>
>         return ops_index;
> --
> 1.8.3.1
>