[dpdk-dev] [PATCH dpdk-dev v3] mempool: sort the rte_mempool_ops by name

[xiangxia.m.yue@gmail.com]

From: Tonghao Zhang <xiangxia.m.yue@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@gmail.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
---
v3:
* fix checkpatches.sh WARNING
* change "initiation -> initialization"

v2:
* use the qsort to sort the mempool_ops.
* tested: https://travis-ci.com/ovn-open-virtual-networks/dpdk-next-net/builds/151894026
---
 lib/librte_mempool/rte_mempool_ops.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/librte_mempool/rte_mempool_ops.c b/lib/librte_mempool/rte_mempool_ops.c
index 22c5251..b0da096 100644
--- a/lib/librte_mempool/rte_mempool_ops.c
+++ b/lib/librte_mempool/rte_mempool_ops.c
@@ -17,6 +17,15 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
 	.num_ops = 0
 };
 
+static int
+compare_mempool_ops(const void *a, const void *b)
+{
+	const struct rte_mempool_ops *m_a = a;
+	const struct rte_mempool_ops *m_b = b;
+
+	return strcmp(m_a->name, m_b->name);
+}
+
 /* add a new ops struct in rte_mempool_ops_table, return its index. */
 int
 rte_mempool_register_ops(const struct rte_mempool_ops *h)
@@ -63,6 +72,13 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
 	ops->get_info = h->get_info;
 	ops->dequeue_contig_blocks = h->dequeue_contig_blocks;
 
+	/*
+	 * sort the rte_mempool_ops by name. the order of the mempool
+	 * lib initialization will not affect rte_mempool_ops index.
+	 */
+	qsort(rte_mempool_ops_table.ops, rte_mempool_ops_table.num_ops,
+	      sizeof(rte_mempool_ops_table.ops[0]), compare_mempool_ops);
+
 	rte_spinlock_unlock(&rte_mempool_ops_table.sl);
 
 	return ops_index;
-- 
1.8.3.1