login: panic: pool_cache_item_magic_check: mbufpl cpu free list modified: item addr 0xfffffd806d732400+16 0x0!=0xf9ef81fdec24a3af
Stopped at      db_enter+0x18:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
 343728  60677      0     0x14000      0x200    1  reaper
*209997  87037      0     0x14000 0x40000200    0K softclock
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398
panic() at panic+0x15c sys/kern/subr_prf.c:207
pool_cache_get(ffffffff82658ba8) at pool_cache_get+0x323 pool_cache_item_magic_check sys/kern/subr_pool.c:1789 [inline]
pool_cache_get(ffffffff82658ba8) at pool_cache_get+0x323 sys/kern/subr_pool.c:1892
pool_get() at pool_get+0x91 sys/kern/subr_pool.c:572
m_get(2,1) at m_get+0x4c sys/kern/uipc_mbuf.c:250
mld6_sendpkt(ffff800000a5d100,83,0) at mld6_sendpkt+0xaf sys/netinet6/mld6.c:410
mld6_fasttimeo() at mld6_fasttimeo+0x162 mld6_checktimer sys/netinet6/mld6.c:363 [inline]
mld6_fasttimeo() at mld6_fasttimeo+0x162 sys/netinet6/mld6.c:341
pffasttimo(ffffffff8254c978) at pffasttimo+0x85 sys/kern/uipc_domain.c:292
timeout_run(ffffffff8254c978) at timeout_run+0xc4 timeout_sync_leave sys/kern/kern_timeout.c:177 [inline]
timeout_run(ffffffff8254c978) at timeout_run+0xc4 sys/kern/kern_timeout.c:477
softclock_thread(ffff800020a10000) at softclock_thread+0x16a sys/kern/kern_timeout.c:558
end trace frame: 0x0, count: 5
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports.  Insufficient info makes it difficult to find and fix bugs.
ddb{0}> 
ddb{0}> set $lines = 0
ddb{0}> set $maxwidth = 0
ddb{0}> show panic
pool_cache_item_magic_check: mbufpl cpu free list modified: item addr 0xfffffd806d732400+16 0x0!=0xf9ef81fdec24a3af
ddb{0}> trace
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398
panic() at panic+0x15c sys/kern/subr_prf.c:207
pool_cache_get(ffffffff82658ba8) at pool_cache_get+0x323 pool_cache_item_magic_check sys/kern/subr_pool.c:1789 [inline]
pool_cache_get(ffffffff82658ba8) at pool_cache_get+0x323 sys/kern/subr_pool.c:1892
pool_get() at pool_get+0x91 sys/kern/subr_pool.c:572
m_get(2,1) at m_get+0x4c sys/kern/uipc_mbuf.c:250
mld6_sendpkt(ffff800000a5d100,83,0) at mld6_sendpkt+0xaf sys/netinet6/mld6.c:410
mld6_fasttimeo() at mld6_fasttimeo+0x162 mld6_checktimer sys/netinet6/mld6.c:363 [inline]
mld6_fasttimeo() at mld6_fasttimeo+0x162 sys/netinet6/mld6.c:341
pffasttimo(ffffffff8254c978) at pffasttimo+0x85 sys/kern/uipc_domain.c:292
timeout_run(ffffffff8254c978) at timeout_run+0xc4 timeout_sync_leave sys/kern/kern_timeout.c:177 [inline]
timeout_run(ffffffff8254c978) at timeout_run+0xc4 sys/kern/kern_timeout.c:477
softclock_thread(ffff800020a10000) at softclock_thread+0x16a sys/kern/kern_timeout.c:558
end trace frame: 0x0, count: -10
ddb{0}> show registers
rdi                                0
rsi                              0x1
rbp               0xffff800020a25750
rbx               0xffff800020a25800
rdx                             0x8b
rcx                              0x2
rax                              0x1
r8                0xffffffff81ebdc8f    kprintf+0x16f
r9                               0x1
r10               0x6d5e77c31ce9713f
r11               0xe4fd54fa694ca076
r12                     0x3000000008
r13               0xffff800020a25760
r14                            0x100
r15                              0x1
rip               0xffffffff81c5afd8    db_enter+0x18
cs                               0x8
rflags                         0x246
rsp               0xffff800020a25740
ss                              0x10
db_enter+0x18:  addq    $0x8,%rsp
ddb{0}> show proc
PROC (softclock) pid=209997 stat=onproc
    flags process=14000<NOZOMBIE,SYSTEM> proc=40000200<SYSTEM,CPUPEG>
    pri=0, usrpri=50, nice=20
    forw=0xffffffffffffffff, list=0xffff800020a104f0,0xffff800020a10288
    process=0xffff800020a12700 user=0xffff800020a20000, vmspace=0xffffffff82626ed8
    estcpu=0, cpticks=1, pctcpu=0.0
    user=0, sys=1, intr=0
ddb{0}>