RHEL7.1: Softirq hang in fib6_run_gc()

Solution In Progress - Updated -

Issue

  • We see repeated occurrences in the /var/log/messages file of the following at a customer site:
[ 2691.938567] Call Trace:
[ 2691.938572]  [<ffffffff815bb278>] fib6_run_gc+0x28/0x100
[ 2691.938575]  [<ffffffff815b3ecf>] ip6_dst_gc+0x6f/0xf0
[ 2691.938579]  [<ffffffff81503f23>] dst_alloc+0x123/0x170
[ 2691.938582]  [<ffffffff814fdcc8>] ? dev_hard_start_xmit+0x328/0x580
[ 2691.938585]  [<ffffffff815b4b00>] ip6_rt_copy+0x40/0x340
[ 2691.938587]  [<ffffffff815b5a38>] ip6_pol_route.isra.46+0x398/0x480
[ 2691.938589]  [<ffffffff815b5b7a>] ip6_pol_route_output+0x2a/0x30
[ 2691.938592]  [<ffffffff815dc855>] fib6_rule_action+0xc5/0x200
[ 2691.938594]  [<ffffffff815b5b50>] ? ip6_pol_route_input+0x30/0x30
[ 2691.938597]  [<ffffffff81517c16>] fib_rules_lookup+0xd6/0x170
[ 2691.938600]  [<ffffffff815dcb53>] fib6_rule_lookup+0x53/0xa0
[ 2691.938602]  [<ffffffff815b5b50>] ? ip6_pol_route_input+0x30/0x30
[ 2691.938604]  [<ffffffff815b3a74>] ip6_route_output+0x74/0xb0
[ 2691.938607]  [<ffffffff815a5aa3>] ip6_dst_lookup_tail+0x283/0x2a0
[ 2691.938610]  [<ffffffff815a5b23>] ip6_dst_lookup_flow+0x43/0xb0
[ 2691.938613]  [<ffffffff815a455b>] inet6_sk_rebuild_header+0x10b/0x180
[ 2691.938616]  [<ffffffff815532e9>] ? tcp_transmit_skb+0x479/0x900
[ 2691.938618]  [<ffffffff815546ff>] __tcp_retransmit_skb+0x7f/0x5c0
[ 2691.938622]  [<ffffffff81080afd>] ? mod_timer+0x11d/0x240
[ 2691.938624]  [<ffffffff81554e69>] tcp_retransmit_skb+0x19/0x110
[ 2691.938627]  [<ffffffff81556df4>] tcp_retransmit_timer+0x274/0x720
[ 2691.938630]  [<ffffffff81557490>] ? tcp_write_timer_handler+0x1f0/0x1f0
[ 2691.938632]  [<ffffffff81557340>] tcp_write_timer_handler+0xa0/0x1f0
[ 2691.938634]  [<ffffffff815574fc>] tcp_write_timer+0x6c/0x70
[ 2691.938639]  [<ffffffff8107df56>] call_timer_fn+0x36/0x110
[ 2691.938641]  [<ffffffff81557490>] ? tcp_write_timer_handler+0x1f0/0x1f0
[ 2691.938643]  [<ffffffff8107fdcf>] run_timer_softirq+0x21f/0x320
[ 2691.938646]  [<ffffffff81077b2f>] __do_softirq+0xef/0x280
[ 2691.938649]  [<ffffffff81077cf0>] run_ksoftirqd+0x30/0x50
[ 2691.938652]  [<ffffffff8109fc7f>] smpboot_thread_fn+0xff/0x1a0
[ 2691.938654]  [<ffffffff816096a9>] ? schedule+0x29/0x70
[ 2691.938656]  [<ffffffff8109fb80>] ? lg_global_unlock+0xc0/0xc0
[ 2691.938659]  [<ffffffff8109726f>] kthread+0xcf/0xe0
[ 2691.938662]  [<ffffffff810971a0>] ? kthread_create_on_node+0x140/0x140
[ 2691.938665]  [<ffffffff81614158>] ret_from_fork+0x58/0x90

Environment

  • Red Hat Enterprise Linux 7.1
    • kernel-3.10.0-229.7.2.el7
  • Ipv6
  • Following kernel settings related to garbage collection:
net.ipv6.route.gc_elasticity = 8
net.ipv6.route.gc_interval = 30
net.ipv6.route.gc_min_interval = 0
net.ipv6.route.gc_min_interval_ms = 500
net.ipv6.route.gc_thresh = 524288
net.ipv6.route.gc_timeout = 60
net.ipv6.route.max_size = 8388608
net.ipv6.route.min_adv_mss = 1220
net.ipv6.route.mtu_expires = 600

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