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Date: Tue, 14 May 2013 17:11:56 +0200
From: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
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Subject: Re: [Qemu-devel] segfault in aio_bh_poll async.c:80 WAS: Re: kvm
 process disappears
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, "pve-devel@pve.proxmox.com" <pve-devel@pve.proxmox.com>, Michael Roth <mdroth@linux.vnet.ibm.com>

Am 14.05.2013 17:05, schrieb Stefan Hajnoczi:
> On Tue, May 14, 2013 at 4:29 PM, Stefan Priebe - Profihost AG
> <s.priebe@profihost.ag> wrote:
>> Am 10.05.2013 13:09, schrieb Stefan Hajnoczi:
>>> On Fri, May 10, 2013 at 11:07 AM, Stefan Priebe - Profihost AG
>>> <s.priebe@profihost.ag> wrote:
>>>> Am 10.05.2013 09:42, schrieb Stefan Hajnoczi:
>>>>> On Fri, May 10, 2013 at 08:12:39AM +0200, Stefan Priebe - Profihost AG wrote:
>>>>> 3. Either use gdb or an LD_PRELOAD library that catches exit(3) and
>>>>>    _exit(2) and dumps core using abort(3).  Make sure core dumps are
>>>>>    enabled.
>>
>> This time i had a segfault Qemu 1.4.1 plus
>> http://git.qemu.org/?p=qemu.git;a=commitdiff;h=dc7588c1eb3008bda53dde1d6b890cd299758155.
>>
>> aio_bh_poll    async.c:80
>>
>> Code...
>>
>>    for (bh = ctx->first_bh; bh; bh = next) {
>>         next = bh->next;
>>         if (!bh->deleted && bh->scheduled) {
>>             bh->scheduled = 0;
>>             if (!bh->idle)
>>                 ret = 1;
>>             bh->idle = 0;
>>             bh->cb(bh->opaque);
>>         }
>>     }
>>
>>     ctx->walking_bh--;
>>
>>     /* remove deleted bhs */
>>     if (!ctx->walking_bh) {
>>         bhp = &ctx->first_bh;
>>         while (*bhp) {
>>             bh = *bhp;
>> ===== THIS IS THE SEGFAULT LINE =====            if (bh->deleted) {
>>                 *bhp = bh->next;
>>                 g_free(bh);
>>             } else {
>>                 bhp = &bh->next;
>>             }
>>         }
>>     }
>>
>>     return ret;
> 
> Interesting crash.  Do you have the output of "thread apply all bt"?
> 
> I would try looking at the AioContext using "p *ctx", and print out
> the ctx->first_bh linked list.

Hi,

as i can't reproduce no ;-( i just saw the kernel segfault message and
used addr2line and a qemu dbg package to get the code line.

Stefan