On Mon, Sep 09, 2019 at 05:42:02PM +0200, Raimo Niskanen wrote:
> On Wed, Jul 31, 2019 at 05:46:08PM +0200, Raimo Niskanen wrote:
> > On Mon, Jul 29, 2019 at 01:20:58PM +0000, Stuart Henderson wrote:
> > > On 2019-07-29, Raimo Niskanen <raimo+open...@erix.ericsson.se> wrote:
> > > > A new hang, I tried to invstigate:
> > > >
> > > > At July 19 the last log entry from my 'ps' log was from 14:55, which is
> > > > also the time on the 'systat vmstat' screen when it froze. Then the
> > > > machine
> > > > hums along but just after midnight at 00:42:01 the first "/bsd: process:
> > > > table is full" entry appears. That message repeats until I rebooted it
> > > > today at July 29 10:48.
> > > >
> > > > I had a terminal with top running. It was still updating. It showed
> > > > about
> > > > 98% sys and 2% spin on one of 4 CPUs, the others 100% idle. Then (after
> > > > the process table had gotten full) it had 1282 idle processes and 1 on
> > > > processor, which was 'top' itself.
> > > > Memory: Real: 456M/1819M act/tot Free: 14G Cache: 676M Swap: 0K/16G.
> > > >
> > > > I had 8 shells under tmux ready for debugging. 'ls worked.
> > > > 'systat' on one hung. 'top' on another failed with "cannot fork".
> > > > 'exec ps ajxww" printed two lines with /sbin/init and /sbin/slaac
> > > > and then hung. 'exec reboot' did not succeed. Neither did a short
> > > > power
> > > > button, that at least caused a printout "stopping daemon nginx(failed)",
> > > > but got no further. I had to do a hard power off.
> > > >
> > > > My theory now is that our daily tests right before 14:55 started a
> > > > process
> > > > (this process is the top 'top' process with 10:14 execution time) that
> > > > triggers a lock or other contention problem in the kernel which causes
> > > > one CPU to spin in the system, and blocks processes from dying.
> > > > About 10 hours later the process table gets full.
> > > >
> > > > Any, ANY ideas of how to proceed would be appreciated!
> > > >
> > > > Best Regards
> > >
> > > Did you notice any odd waitchan's (WAIT in top output)?
> > >
> > > Maybe set ddb.console=1 in sysctl.conf and reboot (if not already
> > > set), then try to break into DDB during a hang and see how things look
> > > in ps there. (Test breaking into DDB before a hang first so you know
> > > that you can do it .. you can just "c" to continue).
> > >
> > > There might also be clues in things like "sh malloc" or "sh all pools".
> > >
> > > Perhaps you could also get clues from running a kernel built with
> > > 'option WITNESS', you may get some messages in dmesg, or it adds commands
> > > to ddb like "show locks", "show all locks", "show witness" (see ddb(4) for
> > > details).
> >
> > I have enabled Witness, it went so-so. We'll see what it catches.
> >
> > I downloaded 6.5 amd64 src.tar.gz and sys.tar.gz, unpacked them,
> > applied all patches for stable 001-006 and built a kernel with:
> > include "arch/amd64/conf/GENERIC"
> > option MULTIPROCESSOR
> > option MP_LOCKDEBUG
> > option WITNESS
> >
> > Then I activated in /etc/sysctl.conf:
> > ddb.console=1
> > kern.witness.locktrace=1
> > kern.witness.watch=3
> >
> > For fun, I pressed Ctrl+Alt+Esc at the console, got a ddb> prompt and typed
> > "show witness". It printed lots of info, I scrolled down to the end, but
> > during the printout there was an UVM fault:
> >
> > Spin locks:
> > /usr/src/sys/....
> > :
> > bla bla bla
> > :
> > uvm_fault(0xffffffff81e03b50, 0xffff800022368360, 0, 1) -> e
> > kernel: page fault trap, code=0
> > Faulted in DDB: continuing...
> >
> > Then I typed "cont" and it panicked.
> > If anybody want details I took a picture.
> >
> > Have I combined too many debugging options, or is this sh*t that happens?
> >
> > Nevertheless, now the machine is running again, with Witness...
> >
> > I'll be back.
>
> I have encountered some kind of stop, oddly enought not a panic - it
> just sat in ddb and I missed it for a week (or more). Then I did not
> remember what I had planned to do so I "improvised" X-| , but anyway:
>
> ddb{0}> ps
> shows about 350 processes from cron, half of them in state netlock, half
Sorry, that should have been about 1350 processes...
> in state piperd. Then I have my test processes beam.smp: 6 in netlock, 6
> in piperd, about 70 in fsleep, 3 in poll, 3 in select, 4 in kqread.
> Then about 100 more ordinary looking processes...
>
> ddb{0}> trace
> db_enter()...
> softclock(0)...
> softintr_dispatch(0)...
> Xsoftclock(0,0,1388,....)...
> acpicpu_idle()...
> shed_idle(ffffffff81ceff0)...
> end trace frame: 0x0, count: -6
>
> ddb{0}> show locks
> exclusive kernel_lock &kernel_lock r = 0 (0xffffffff81e37b10) locked @
> /usr/src/sys/arch/amd64/amd64/softintr.c:87
> #0 witness_lock+0x41f
> #1 softintr_dispatc+0x56
> #2 Xsoftclock+0x1f
> #3 acpicpu_idle+0x271
> #4 sched_idle+0x235
> #5 proc_trampoline+0x1c
>
> ddb{0}> show nfsnode
> size 5476515891122113356 flag 0 vnode 0xd080c7d8 accstamp 1099511681152
>
> (I think the size looks strange)
>
> Then I tried show map and got a protection fault trap, gave up and
> rebooted.
>
> That was it! Next time I will try:
> trace
> ps
> show malloc
> show all pools
> show locks
> show all locks
> unless anyone has got more or better suggestions...
>
> Best Regards
> --
>
> / Raimo Niskanen, Erlang/OTP, Ericsson AB
--
/ Raimo Niskanen, Erlang/OTP, Ericsson AB
