Date: Mon, 23 Mar 2015 01:41:55 +0100 From: Zbigniew Bodek <zbb@freebsd.org> To: Paul Mather <paul@gromit.dlib.vt.edu> Cc: "freebsd-arm@freebsd.org" <arm@freebsd.org> Subject: Re: panic: pmap_demote_section: No l2_bucket for wired mapping Message-ID: <CALF_Txn85FYTNsvnjUpSc7aGaNB=wZ8pSGP7nUBwQvjqvOx%2Bvg@mail.gmail.com> In-Reply-To: <1EFF2C41-456C-476E-9BA8-712E62DF0D4E@gromit.dlib.vt.edu> References: <AF7A0CA1-6A0C-47CC-B096-646BBD235862@freebsd.org> <1EFF2C41-456C-476E-9BA8-712E62DF0D4E@gromit.dlib.vt.edu>
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2015-03-22 20:45 GMT+01:00 Paul Mather <paul@gromit.dlib.vt.edu>: > On Mar 22, 2015, at 7:54 AM, Michael Tuexen <tuexen@freebsd.org> wrote: > >> 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 > > > I get this panic when booting to multi-user on my newly-updated BBB (FreeBSD 11.0-CURRENT #0 r280350). As pointed out later in this thread, setting vm.pmap.sp_enabled=0 prevents the panic (so far) and allows booting. > > Cheers, > > Paul. > I was able to reproduce this on my R-Pi too. The bug may be related to shared libraries mapping since excluding pmap_enter_section() (the one in the pmap_enter_object() that is responsible for doing the work for shared libraries mappings) results in normal operation even with page promotion/demotion enabled. I will try to find some time to look into that to ensure that this is not just covering the problem. If it doesn't then we may consider disabling pmap_enter_section() (by adding "return FALSE;") to have WA (without disabling superpages) until we find the real solution. pmap_enter_section() was being used very rarely before shared libraries superpage mappings were enabled so it is reasonable to think that the bug is somewhere around. Please let me know in case you find something. Best regards zbb
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