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* [dpdk-users] Mbuf Free Segfaults in Secondary application
@ 2019-08-16 19:02 Kyle Ames
  0 siblings, 0 replies; only message in thread
From: Kyle Ames @ 2019-08-16 19:02 UTC (permalink / raw)
  To: users

I'm running into an issue with primary/secondary DPDK processes. I am using DPDK 19.02.

I'm trying to explore a setup where one process pulls packets off the NIC, and then sends them over a rte_ring for additional processing. Unlike the client_server_mp example, I don't need to send the packets out a given port in the client. Once the client is done with them they can just go back into the mbuf mempool. In order to test this, I took the mp_client example and modified it immediately call rte_pktmbuf_free on the packet and not do anything else with it after receiving the packet over the shared ring.

This works fine for the first 1.5*N packets, where N is the value set for the per-lcore cache. Calling rte_pktmbuf_free on the next packet will segfault in bucket_enqueue. (backtrace from GDB below)

Program received signal SIGSEGV, Segmentation fault.
0x0000000000593822 in bucket_enqueue ()
Missing separate debuginfos, use: debuginfo-install glibc-2.17-196.el7_4.2.x86_64 libgcc-4.8.5-16.el7.x86_64 numactl-libs-2.0.9-6.el7_2.x86_64
(gdb) backtrace
#0  0x0000000000593822 in bucket_enqueue ()
#1  0x00000000004769f1 in rte_mempool_ops_enqueue_bulk (n=1, obj_table=0x7fffffffe398, mp=<optimized out>)
    at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mempool.h:704
#2  __mempool_generic_put (cache=<optimized out>, n=1, obj_table=0x7fffffffe398, mp=<optimized out>)
    at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mempool.h:1263
#3  rte_mempool_generic_put (cache=<optimized out>, n=1, obj_table=0x7fffffffe398, mp=<optimized out>)
    at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mempool.h:1285
#4  rte_mempool_put_bulk (n=1, obj_table=0x7fffffffe398, mp=<optimized out>) at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mempool.h:1308
#5  rte_mempool_put (obj=0x100800040, mp=<optimized out>) at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mempool.h:1326
#6  rte_mbuf_raw_free (m=0x100800040) at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mbuf.h:1185
#7  rte_pktmbuf_free_seg (m=<optimized out>) at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mbuf.h:1807
#8  rte_pktmbuf_free (m=0x100800040) at /home/kames/code/3rdparty/dpdk-hack/dpdk/build/include/rte_mbuf.h:1828
#9  main (argc=<optimized out>, argv=<optimized out>)
    at /home/kames/code/3rdparty/dpdk-hack/dpdk/examples/multi_process/client_server_mp/mp_client/client.c:90

I changed the size a few times, and the packet in the client that segfaults on free is always the 1.5N'th packet. This happens even if I set the cache_size to zero on mbuf pool creation. (The first mbuf free immediately segfaults)

I'm a bit stuck at the moment. There's clearly a pattern/interaction of some sort, but I don't know what it is or what to do about it. Is this even the right approach for such a scenario?

-Kyle Ames

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2019-08-16 19:02 [dpdk-users] Mbuf Free Segfaults in Secondary application Kyle Ames

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