panic: pmap_demote_section: No l2_bucket for wired mapping

[Michael Tuexen]

Dear all,

running head on a Raspberry Pi became unstable. When running
r280329 for a while (the machine is exposed to the Internet, so
ssh logins are continuously tried), the machine panics:

panic: pmap_demote_section: No l2_bucket for wired mapping
KDB: enter: panic
[ thread pid 15 tid 100049 ]
Stopped at      $d.13:  ldrb    r15, [r15, r15, ror r15]!
db> where
Tracing pid 15 tid 100049 td 0xc25cc660
db_trace_self() at db_trace_self
         pc = 0xc04ed3a0  lr = 0xc0132110 ($a.30+0xf4)
         sp = 0xdbf88980  fp = 0xdbf88998
        r10 = 0xc070598c
$a.30() at $a.30+0xf4
         pc = 0xc0132110  lr = 0xc0131a98 ($a.12+0x270)
         sp = 0xdbf889a0  fp = 0xdbf88a40
         r4 = 0x00000000  r5 = 0x00000000
         r6 = 0x00000072 r10 = 0xc070598c
$a.12() at $a.12+0x270
         pc = 0xc0131a98  lr = 0xc0131800 (db_command_loop+0x5c)
         sp = 0xdbf88a48  fp = 0xdbf88a58
         r4 = 0xc0543cf6  r5 = 0xc0563963
         r6 = 0xc0705978  r7 = 0xc0619a84
         r8 = 0xc06fba20  r9 = 0xc06fba24
        r10 = 0xdbf88c28
db_command_loop() at db_command_loop+0x5c
         pc = 0xc0131800  lr = 0xc013423c (db_trap+0xd8)
         sp = 0xdbf88a60  fp = 0xdbf88b80
         r4 = 0x00000000  r5 = 0xc0705984
         r6 = 0xc06fba48 r10 = 0xdbf88c28
db_trap() at db_trap+0xd8
         pc = 0xc013423c  lr = 0xc02d1180 (kdb_trap+0xbc)
         sp = 0xdbf88b88  fp = 0xdbf88ba8
         r4 = 0x00000000  r5 = 0x00000001
         r6 = 0xc06fba48  r7 = 0xc0619a84
kdb_trap() at kdb_trap+0xbc
         pc = 0xc02d1180  lr = 0xc0500784 (undefinedinstruction+0x2b8)
         sp = 0xdbf88bb0  fp = 0xdbf88c20
         r4 = 0x00000000  r5 = 0x00000000
         r6 = 0xc050041c  r7 = 0xe7ffffff
         r8 = 0xc25cc660  r9 = 0xc02d0a6c
        r10 = 0xdbf88c28
undefinedinstruction() at undefinedinstruction+0x2b8
         pc = 0xc0500784  lr = 0xc04eea54 (exception_exit)
         sp = 0xdbf88c28  fp = 0xdbf88cc0
         r4 = 0xc05639b8  r5 = 0xdbf88d14
         r6 = 0xc0590e4a  r7 = 0xc06edf78
         r8 = 0xc25cc660  r9 = 0xc07074d8
        r10 = 0xc06edde0
exception_exit() at exception_exit
         pc = 0xc04eea54  lr = 0xc02d0a60 (kdb_enter+0x3c)
         sp = 0xdbf88cb8  fp = 0xdbf88cc0
         r0 = 0xc06fba34  r1 = 0x00000000
         r2 = 0xc056701c  r3 = 0x000000aa
         r4 = 0xc05639b8  r5 = 0xdbf88d14
         r6 = 0xc0590e4a  r7 = 0xc06edf78
         r8 = 0xc25cc660  r9 = 0xc07074d8
        r10 = 0xc06edde0 r12 = 0x00000000
$a.14() at $a.14
         pc = 0xc02d0a70  lr = 0xc0297928 ($a.14+0xb4)
         sp = 0xdbf88cc8  fp = 0xdbf88ce8
         r4 = 0x00000100 r10 = 0xc06edde0
$a.14() at $a.14+0xb4
         pc = 0xc0297928  lr = 0xc0297864 ($d.13)
         sp = 0xdbf88cf0  fp = 0xdbf88d08
         r4 = 0xc06ede78  r5 = 0xc0590e4a
         r6 = 0xdbf88d14  r7 = 0xc06edde0
         r8 = 0xc0d54800  r9 = 0x00000203
        r10 = 0xc2bda0bc
$d.13() at $d.13
         pc = 0xc0297864  lr = 0xc04f4bd0 ($a.16+0x62c)
         sp = 0xdbf88d20  fp = 0xdbf88d60
         r4 = 0xc2bda0bc  r5 = 0x0bf09c2e
         r6 = 0xc2c01df0  r7 = 0x20300000
$a.16() at $a.16+0x62c
         pc = 0xc04f4bd0  lr = 0xc04fabd8 ($a.110+0xc0)
         sp = 0xdbf88d68  fp = 0xdbf88da8
         r4 = 0xc152a830  r5 = 0x20300000
         r6 = 0xd9fa0000  r7 = 0x00000203
         r8 = 0xc2bda0bc  r9 = 0xc2bda0cc
        r10 = 0x00000000
$a.110() at $a.110+0xc0
         pc = 0xc04fabd8  lr = 0xc04db974 ($a.27+0x84)
         sp = 0xdbf88db0  fp = 0xdbf88e28
         r4 = 0xc0d57500  r5 = 0x00000005
         r6 = 0x00000562  r7 = 0x00000006
         r8 = 0x00000001  r9 = 0xc058d0d7
        r10 = 0xc058d0d7
$a.27() at $a.27+0x84
         pc = 0xc04db974  lr = 0xc0265bc8 (fork_exit+0x80)
         sp = 0xdbf88e30  fp = 0xdbf88e48
         r4 = 0xc25cc660  r5 = 0xc2760000
         r6 = 0xc04da8a4  r7 = 0x00000000
         r8 = 0xdbf88e50  r9 = 0xc06fb5c0
        r10 = 0xc065ae00
fork_exit() at fork_exit+0x80
         pc = 0xc0265bc8  lr = 0xc04ee9e4 (swi_exit)
         sp = 0xdbf88e50  fp = 0x00000000
         r4 = 0xc04da8a4  r5 = 0x00000000
         r6 = 0xc06fc70c  r7 = 0xc06fb5c4
         r8 = 0x00000104 r10 = 0xc065ae00
swi_exit() at swi_exit
         pc = 0xc04ee9e4  lr = 0xc04ee9e4 (swi_exit)
         sp = 0xdbf88e50  fp = 0x00000000
db>  

It might be related to
https://svnweb.freebsd.org/changeset/base/280324

Any idea what is going on?

Best regards
Michael