Date: Tue, 26 Apr 2016 23:28:42 +0200 From: Svatopluk Kraus <onwahe@gmail.com> To: bob prohaska <fbsd@www.zefox.net> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: Another reboot hang Message-ID: <CAFHCsPXjxHzHr2-4jiLJThSLQGJOqF9Z3hWXfF=3nH4F=%2BgfFg@mail.gmail.com> In-Reply-To: <20160426204016.GO71221@www.zefox.net> References: <20160426183030.GN71221@www.zefox.net> <CAFHCsPU94vrXgHRSNPvwAFNE0Hnd-6zzhsCSUGDGkVyGQ6jNMg@mail.gmail.com> <20160426204016.GO71221@www.zefox.net>
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On Tue, Apr 26, 2016 at 10:40 PM, bob prohaska <fbsd@www.zefox.net> wrote:
> On Tue, Apr 26, 2016 at 10:18:24PM +0200, Svatopluk Kraus wrote:
>> > exception_exit() at exception_exit
>> > pc = 0xc05687fc lr = 0xc0515a44 (ffs_sync+0x104)
>> > sp = 0xd75ebb88 fp = 0xd75ebba8
>> > r0 = 0x00000004 r1 = 0xc3a5f000
>> > r2 = 0xc3fdb2c0 r3 = 0xc3a5f000
>> > r4 = 0xc0620546 r5 = 0x00000001
>> > r6 = 0xc3fdb2c0 r7 = 0x00000608
>> > r8 = 0x00000000 r9 = 0xc3fdb2b0
>> > r10 = 0xd75ebbf0 r12 = 0xc061cf05
>>
>> The break to debugger happened here. So system was in
>> __mtx_lock_flags() called from ffs_sync(). It's impossible to say from
>> the backtrace if system was stuck or you just break it there. However,
>> interrupts was working, so system was not dead totally. One method how
>> to learn more is to break to debugger repeatedly to see if system is
>> stuck to one place or not. You also can try to type the following
>> commands in ddb to see if there is any deadlock.
>>
>> show all pcpu
>> show all procs
>> show all locks
>>
>> For the second command, kernel must be built with WITNESS option.
>>
>
> In past occurences I've waited considerably longer than the normal
> reboot time, so it really did seem stuck. The hangs aren't repeatable,
> so I'll try the first and third comands at the next opportunity and
> turn on WITNESS as a last resort; it really slows the machine down.
Hmm, it's third command which needs WITNESS option. I added 'show all
pcpu' on first place later and did not fix the reference. By breaking
to debugger repeatedly I mean - type 'c' in ddb ('continue' command)
and then break to debugger again.
>
> Thanks for your help!
>
> bob prohaska
>
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