hi all: I want to send sk_buff by "dev_queue_xmit", when I just send 2 packets, the network card may be hang. I want to know how to debug this condition. the /var/log/messages is: ######################################### [root@10g-host2 test]# tail -f /var/log/messages Sep 29 10:38:22 10g-host2 acpid: waiting for events: event logging is off Sep 29 10:38:23 10g-host2 acpid: client connected from 2018[68:68] Sep 29 10:38:23 10g-host2 acpid: 1 client rule loaded Sep 29 10:38:24 10g-host2 automount[2210]: lookup_read_master: lookup(nisplus): couldn't locate nis+ table auto.master Sep 29 10:38:24 10g-host2 mcelog: failed to prefill DIMM database from DMI data Sep 29 10:38:24 10g-host2 xinetd[2246]: xinetd Version 2.3.14 started with libwrap loadavg labeled-networking options compiled in. Sep 29 10:38:24 10g-host2 xinetd[2246]: Started working: 0 available services Sep 29 10:38:25 10g-host2 abrtd: Init complete, entering main loop Sep 29 10:39:41 10g-host2 kernel: vmalloc mmap_buf=ffffc90016e29000 mmap_size=4096 Sep 29 10:39:41 10g-host2 kernel: insmod module wsmmap successfully! Sep 29 10:39:49 10g-host2 kernel: mmap_buf + 1024 is ffffc90016e29400 Sep 29 10:39:49 10g-host2 kernel: data ffffc90016e2942a, len is 42 Sep 29 10:39:49 10g-host2 kernel: udp data ffffc90016e29422 Sep 29 10:39:49 10g-host2 kernel: ip data ffffc90016e2940e Sep 29 10:39:49 10g-host2 kernel: eth data ffffc90016e29400 Sep 29 10:39:49 10g-host2 kernel: h_source is ffffc90016e29406, dev_addr is ffff880c235c4750, len is 6result is 0 Sep 29 10:39:50 10g-host2 kernel: mmap_buf + 1024 is ffffc90016e29400 Sep 29 10:39:50 10g-host2 kernel: data ffffc90016e2942a, len is 42 Sep 29 10:39:50 10g-host2 kernel: udp data ffffc90016e29422 Sep 29 10:39:50 10g-host2 kernel: ip data ffffc90016e2940e Sep 29 10:39:50 10g-host2 kernel: eth data ffffc90016e29400 Sep 29 10:39:50 10g-host2 kernel: h_source is ffffc90016e29406, dev_addr is ffff880c235c4750, len is 6result is 0 Sep 29 10:39:52 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: Detected Tx Unit Hang Sep 29 10:39:52 10g-host2 kernel: Tx Queue <11> Sep 29 10:39:52 10g-host2 kernel: TDH, TDT <0>, <5> Sep 29 10:39:52 10g-host2 kernel: next_to_use <5> Sep 29 10:39:52 10g-host2 kernel: next_to_clean <0> Sep 29 10:39:52 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: tx_buffer_info[next_to_clean] Sep 29 10:39:52 10g-host2 kernel: time_stamp <fffd3dd8> Sep 29 10:39:52 10g-host2 kernel: jiffies <fffd497f> Sep 29 10:39:52 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: tx hang 1 detected on queue 11, resetting adapter Sep 29 10:39:52 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: Reset adapter Sep 29 10:39:52 10g-host2 kernel: ixgbe 0000:03:00.0: master disable timed out Sep 29 10:39:53 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: detected SFP+: 5 Sep 29 10:39:54 10g-host2 kernel: ixgbe 0000:03:00.0: eth2: NIC Link is Up 10 Gbps, Flow Control: RX/TX ######################################### some information of my computer is: ######################################### ethtool -i eth2 driver: ixgbe version: 3.21.2 firmware-version: 0x1bab0001 bus-info: 0000:03:00.0 supports-statistics: yes supports-test: yes supports-eeprom-access: yes supports-register-dump: yes supports-priv-flags: no LSB Version: :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch Distributor ID: CentOS Description: CentOS release 6.5 (Final) Release: 6.5 Codename: Final ######################################### kernel version is: 2.6.32-431.el6.x86_64 Thank you for your help.