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References: <20150127203103.GZ15484@glebius.int.ru>
 <20150128104842.GL42409@kib.kiev.ua>
 <20150128182230.GB15484@glebius.int.ru>
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 <20150128193315.GC15484@glebius.int.ru>
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Date: Mon, 9 Feb 2015 17:32:59 -0800
Message-ID: <CAFgRE9Gb0NLo+5J9iwKDvecMctP=bjzMwaV7bM8Q+=JY-1L6Hg@mail.gmail.com>
Subject: Re: panic in softdep_slowdown()
From: Neel Natu <neelnatu@gmail.com>
To: Gleb Smirnoff <glebius@freebsd.org>
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Cc: Konstantin Belousov <kostikbel@gmail.com>,
 "current@freebsd.org" <current@freebsd.org>, Peter Grehan <grehan@freebsd.org>
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A fix for this panic was submitted by kib@ as r277922:
https://svnweb.freebsd.org/base?view=revision&revision=277922

best
Neel

On Wed, Jan 28, 2015 at 11:54 AM, Neel Natu <neelnatu@gmail.com> wrote:
> Hi Gleb,
>
> On Wed, Jan 28, 2015 at 11:33 AM, Gleb Smirnoff <glebius@freebsd.org> wrote:
>> On Wed, Jan 28, 2015 at 09:04:42PM +0200, Konstantin Belousov wrote:
>> K> > I can't see where integer divide fault can happen with stat_flush_threads=1 :(
>> K>
>> K> Look at the exact asm instruction which faulted, also look at the registers
>> K> content.
>> K>
>> K> It might be hypervisor bug, after all.
>>
>> Yes, for me it looks like it. %edx should be one as well as -0x44(%rbp).
>>
>> 0xffffffff80895d43 <softdep_slowdown+435>:      mov    -0x20(%rbp),%ecx
>> 0xffffffff80895d46 <softdep_slowdown+438>:      mov    %ecx,%edx
>> 0xffffffff80895d48 <softdep_slowdown+440>:      shr    $0x1f,%edx
>> 0xffffffff80895d4b <softdep_slowdown+443>:      add    %edx,%ecx
>> 0xffffffff80895d4d <softdep_slowdown+445>:      sar    %ecx
>> 0xffffffff80895d4f <softdep_slowdown+447>:      mov    0xffffffff80ee24c8,%edx
>> 0xffffffff80895d56 <softdep_slowdown+454>:      mov    %rax,-0x40(%rbp)
>> 0xffffffff80895d5a <softdep_slowdown+458>:      mov    %ecx,%eax
>> 0xffffffff80895d5c <softdep_slowdown+460>:      mov    %edx,-0x44(%rbp)
>> 0xffffffff80895d5f <softdep_slowdown+463>:      cltd
>> 0xffffffff80895d60 <softdep_slowdown+464>:      mov    -0x44(%rbp),%ecx
>> 0xffffffff80895d63 <softdep_slowdown+467>:      idiv   %ecx
>>
>> (kgdb) p &stat_flush_threads
>> $5 = (int *) 0xffffffff80ee24c8
>> (kgdb) info registers
>> rax            0x12b86  76678
>> rbx            0x4      4
>> rcx            0x0      0
>> rdx            0x0      0
>> rsi            0x3e8    1000
>> rdi            0x99     153
>> rbp            0xfffffe001eb5f2b0       0xfffffe001eb5f2b0
>> ...
>> (kgdb) p *(int *)($rbp - 0x44)
>> $4 = 0
>> (kgdb) p *(int *)($rbp - 0x40)
>> $8 = 0
>> (kgdb) p &max_softdeps_hard
>> $11 = (int *) 0xfffffe001eb5f290
>> (kgdb) p (int *)($rbp - 0x20)
>> $12 = (int *) 0xfffffe001eb5f290
>> (kgdb) p max_softdeps_hard
>> $10 = 153357
>>
>
> Can you upload the core file and the kernel someplace that I can access?
>
> best
> Neel
>
>> --
>> Totus tuus, Glebius.
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