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

[Tonghao Zhang]

On Mon, Mar 2, 2020 at 9:45 PM Jerin Jacob <jerinjacobk at gmail.com> wrote:
>
> 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?
The implementation is easy, and the number of mempool driver is not too large.
But we can use the qsort_r to implement it.
>
> > +       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
> >



-- 
Thanks,
Tonghao