After booting a GENERIC kernel with the addition of WITNESS+INVARIANTS+INVARIANTS_SUPPORT the following LRO is observed shortly after every boot: Mar 29 12:27:37 box kernel: lock order reversal: Mar 29 12:27:37 box kernel: 1st 0xfffff8000474d190 if_addr_lock (if_addr_lock) @ /usr/src/sys/netinet/igmp.c:1708 Mar 29 12:27:37 box kernel: 2nd 0xffffffff81e68d60 ifnet_rw (ifnet_rw) @ /usr/src/sys/net/if.c:258 Mar 29 12:27:37 box kernel: stack backtrace: Mar 29 12:27:37 box kernel: #0 0xffffffff80aa0010 at witness_debugger+0x70 Mar 29 12:27:37 box kernel: #1 0xffffffff80a9ff03 at witness_checkorder+0xe23 Mar 29 12:27:37 box kernel: #2 0xffffffff80a3df3d at __rw_rlock+0x8d Mar 29 12:27:37 box kernel: #3 0xffffffff80b28210 at ifnet_byindex+0x20 Mar 29 12:27:37 box kernel: #4 0xffffffff80b99a1d at igmp_intr+0x1d Mar 29 12:27:37 box kernel: #5 0xffffffff80b48a60 at netisr_dispatch_src+0x80 Mar 29 12:27:37 box kernel: #6 0xffffffff80b99826 at igmp_v1v2_queue_report+0x1c6 Mar 29 12:27:37 box kernel: #7 0xffffffff80b9774d at igmp_fasttimo+0x50d Mar 29 12:27:37 box kernel: #8 0xffffffff80ac2f94 at pffasttimo+0x54 Mar 29 12:27:37 box kernel: #9 0xffffffff80a59048 at softclock_call_cc+0x158 Mar 29 12:27:37 box kernel: #10 0xffffffff80a5942c at softclock+0x7c Mar 29 12:27:37 box kernel: #11 0xffffffff80a07e99 at intr_event_execute_handlers+0x99 Mar 29 12:27:37 box kernel: #12 0xffffffff80a08186 at ithread_loop+0xb6 Mar 29 12:27:37 box kernel: #13 0xffffffff80a05584 at fork_exit+0x84 Mar 29 12:27:37 box kernel: #14 0xffffffff80e9052e at fork_trampoline+0xe Mar 29 12:27:37 box kernel: lock order reversal: Mar 29 12:27:37 box kernel: 1st 0xfffff8000474d190 if_addr_lock (if_addr_lock) @ /usr/src/sys/netinet/igmp.c:1708 Mar 29 12:27:37 box kernel: 2nd 0xfffffe0000edb218 re0 (network driver) @ /usr/src/sys/dev/re/if_re.c:2912 Mar 29 12:27:37 box kernel: stack backtrace: Mar 29 12:27:37 box kernel: #0 0xffffffff80aa0010 at witness_debugger+0x70 Mar 29 12:27:37 box kernel: #1 0xffffffff80a9ff03 at witness_checkorder+0xe23 Mar 29 12:27:37 box kernel: #2 0xffffffff80a21add at __mtx_lock_flags+0x9d Mar 29 12:27:37 box kernel: #3 0xffffffff8078d9e9 at re_start+0x29 Mar 29 12:27:37 box kernel: #4 0xffffffff80b2f72d at if_transmit+0x10d Mar 29 12:27:37 box kernel: #5 0xffffffff80b317e0 at ether_output+0x750 Mar 29 12:27:37 box kernel: #6 0xffffffff80bac229 at ip_output+0x1439 Mar 29 12:27:37 box kernel: #7 0xffffffff80b99c7d at igmp_intr+0x27d Mar 29 12:27:37 box kernel: #8 0xffffffff80b48a60 at netisr_dispatch_src+0x80 Mar 29 12:27:37 box kernel: #9 0xffffffff80b99826 at igmp_v1v2_queue_report+0x1c6 Mar 29 12:27:37 box kernel: #10 0xffffffff80b9774d at igmp_fasttimo+0x50d Mar 29 12:27:37 box kernel: #11 0xffffffff80ac2f94 at pffasttimo+0x54 Mar 29 12:27:37 box kernel: #12 0xffffffff80a59048 at softclock_call_cc+0x158 Mar 29 12:27:37 box kernel: #13 0xffffffff80a5942c at softclock+0x7c Mar 29 12:27:37 box kernel: #14 0xffffffff80a07e99 at intr_event_execute_handlers+0x99 Mar 29 12:27:37 box kernel: #15 0xffffffff80a08186 at ithread_loop+0xb6 Mar 29 12:27:37 box kernel: #16 0xffffffff80a05584 at fork_exit+0x84 Mar 29 12:27:37 box kernel: #17 0xffffffff80e9052e at fork_trampoline+0xe There's seemingly no system impact - everything (including the network) works fine. Tested on FreeBSD 11.1-RELEASE-p8 running on amd64.
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