On Fri, May 11, 2018 at 12:08:33PM -0700, Eric Dumazet wrote:

On 05/11/2018 11:41 AM, Marcelo Ricardo Leitner wrote:

quoted

But calling ip6_xmit with rcu_read_lock is expected. tcp stack also
does it.
Thus I think this is more of an issue with IPv6 stack. If a host has
an extensive ip6tables ruleset, it probably generates this more
easily.

quoted

quoted

 sctp_v6_xmit+0x4a5/0x6b0 net/sctp/ipv6.c:225
 sctp_packet_transmit+0x26f6/0x3ba0 net/sctp/output.c:650
 sctp_outq_flush+0x1373/0x4370 net/sctp/outqueue.c:1197
 sctp_outq_uncork+0x6a/0x80 net/sctp/outqueue.c:776
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1820 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
 sctp_do_sm+0x596/0x7160 net/sctp/sm_sideeffect.c:1191
 sctp_generate_heartbeat_event+0x218/0x450 net/sctp/sm_sideeffect.c:406
 call_timer_fn+0x230/0x940 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]

Having this call from a timer means it wasn't processing sctp stack
for too long.

I feel the problem is that this part is looping, in some infinite loop.

I have seen this stack traces in other reports.

Checked mail history now, seems at least two other reports on RCU
stalls had sctp_generate_heartbeat_event involved.

Maybe some kind of list corruption.

Could be.
Do we know if it generated a flood of packets?

  Marcelo