Re: svn commit: r360233 - in head: contrib/jemalloc . . . : This partially breaks a 2-socket 32-bit powerpc (old PowerMac G4) based on head -r360311

On 2020-May-3, at 01:26, nonameless at ukr.net wrote:




> --- Original message ---
> From: "Mark Millard" <[email protected]>
> Date: 3 May 2020, 04:47:14
> 
> 
> 
>> [I'm only claiming the new jemalloc is involved and that
>> reverting avoids the problem.]
>> 
>> I've been reporting to some lists problems with:
>> 
>> dhclient
>> sendmail
>> rpcbind
>> mountd
>> nfsd
>> 
>> getting SIGSEGV (signal 11) crashes and some core
>> dumps on the old 2-socket (1 core per socket) 32-bit
>> PowerMac G4 running head -r<span data-ukrnet-code="360311">360311</span>.
>> 
>> Mikaël Urankar sent a note suggesting that I try
>> testing reverting head -r<span data-ukrnet-code="360233">360233</span> for my head -r<span data-ukrnet-code="360311">360311</span>
>> context. He got it right . . .
>> 
>> 
>> Context:
>> 
>> The problem was noticed by an inability to have
>> other machines do a:
>> 
>> mount -onoatime,soft OLDPOWERMAC-LOCAL-IP:/... /mnt
>> 
>> sort of operation and to have succeed. By contrast, on
>> the old PowerMac G4 I could initiate mounts against
>> other machines just fine.
>> 
>> I do not see any such problems on any of (all based
>> on head -r360311):
>> 
>> powerpc64 (old PowerMac G5 2-sockets with 2 cores each)
>> armv7 (OrangePi+ 2ed)
>> aarch64 (Rock64, RPi4, RPi3,
>> OverDrive <span data-ukrnet-code="1000">1000</span>,
>> Macchiatobin Double Shot)
>> amd64 (ThreadRipper 1950X)
>> 
>> So I expect something 32-bit powerpc specific
>> is somehow involved, even if jemalloc is only
>> using whatever it is.
>> 
>> (A kyua run with a debug kernel did not find other
>> unexpected signal 11 sources on the 32-bit PowerMac
>> compared to past kyua runs, at least that I noticed.
>> There were a few lock order reversals that I do not
>> know if they are expected or known-safe or not.
>> I've reported those reversals to the lists as well.)
>> 
>> 
>> Recent experiments based on the suggestion:
>> 
>> Doing the buildworld, buildkernel and installing just
>> the new kernel and rebooting made no difference.
>> 
>> But then installing the new world and rebooting did
>> make things work again: I no longer get core files
>> for the likes of (old cores from before the update):
>> 
>> # find / -name "*.core" -print
>> /var/spool/clientmqueue/sendmail.core
>> /rpcbind.core
>> /mountd.core
>> /nfsd.core
>> 
>> Nor do I see the various notices for sendmail
>> signal 11's that did not leave behind a core file
>> --or for dhclient (no core file left behind).
>> And I can mount the old PowerMac's drive from
>> other machines just fine.
>> 
>> 
>> Other notes:
>> 
>> I do not actively use sendmail but it was left
>> to do its default things, partially to test if
>> such default things are working. Unfortunately,
>> PowerMacs have a problematical status under
>> FreeBSD and my context has my historical
>> experiments with avoiding various problems.
>> 
>> ===
>> Mark Millard
>> marklmi at yahoo.com
>> ( dsl-only.net went
>> away in early <span data-ukrnet-code="2018">2018</span>-Mar)
>> 
> 
> Hi Mark,
> 
> It should be fixed, but not by reverting to old version. We can't stuck on old version because of ancient hardware. I think upstream is not interested in support such hardware. So, it have to patched locally.

Observing and reporting the reverting result is an initial
part of problem isolation. I made no request for FreeBSD
to give up on using the updated jemalloc. (Unfortunately,
I'm not sure what a good next step of problem isolation
might be for the dual-socket PowerMac G4 context.)

Other than reverting, no patch is known for the issue at
this point. More problem isolation is needed first.

While I do not have access, https://wiki.freebsd.org/powerpc
lists more modern 32-bit powerpc hardware as supported:
MPC85XX evaluation boards and AmigaOne A1222 (powerpcspe).
(The AmigaOne A1222 seems to be dual-ore/single-socket.)

So folks with access to one of those may want to see
if they also see the problem(s) with head -r360233 or
later.

Another interesting context to test could be single-socket
with just one core. (I might be able to do that on another
old PowerMac, booting the same media after moving the
media.)

If I understand right, the most common 32-bit powerpc
tier 2 hardware platforms may still be old PowerMac's.
They are considered supported and "mature", instead of
just "stable". See https://wiki.freebsd.org/powerpc .
However, the reality is that there are various problems
for old PowerMacs (32-bit and 64-bit, at least when
there is more than one socket present). The wiki page
does not hint at such. (I'm not sure about
single socket/multi-core PowerMacs: no access to
such.)

It is certainly possible for some problem to happen
that would lead to dropping the supported-status
for some or all old 32-bit PowerMacs, even as tier 2.
But that has not happened yet and I'd have no say in
such a choice.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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