[CRIU] crash when restoring with current git master?

[Pavel Emelyanov]

On 06/04/2015 07:52 PM, Tycho Andersen wrote:
> On Fri, Apr 24, 2015 at 10:40:39PM +0300, Pavel Emelyanov wrote:
>> On 04/24/2015 09:41 PM, Tycho Andersen wrote:
>>> On Fri, Apr 24, 2015 at 09:15:46PM +0300, Cyrill Gorcunov wrote:
>>>> On Fri, Apr 24, 2015 at 11:53:41AM -0600, Tycho Andersen wrote:
>>>>> Hi all,
>>>>>
>>>>> When doing a c/r of lxc containers (vivid host, vivid container), I'm
>>>>> getting a crash sometimes. It looks like something is dying in the
>>>>> restorer blob:
>>>>>
>>>>> http://paste.ubuntu.com/10880188/
>>>>>
>>>>> Has anyone seen this? Any idea what's causing it?
>>>>
>>>> Didn't see like this before. But definitely something goes bad in cgroups at least
>>>>
>>>>  | (00.084962)    333: Error (files-reg.c:1055): File sys/fs/cgroup/perf_event/lxc/u2-30/cgroup.procs has bad size 17 (expect 11)
>>>>
>>>> someone write another task there?
>>>
>>> Ah, whoops. I missed this somehow in the log. That's probably what's
>>> happening. Note that criu hangs on this error; the attached patch
>>> fixes the hang.
>>
>>> +
>>> +err:
>>> +	futex_abort_and_wake(&task_entries->nr_in_progress);
>>> +	return -1;
>>>  }
>>
>> But this thing has never been here. Instead, when child gets an error is
>> exits and then the sigchld_handler() runs and does futex_abort_and_wake().
>> Why hasn't this logic worked this time?
> 
> I just got around to looking at this again, and I'm seeing:
> 
> ShdPnd: 0000000000010000
> SigBlk: fffffffe7ffbfeff
> 
> in the parent of the process that died. If my math is right that's the
> 17th bit, which is SIGCHLD. I don't know enough about why that
> wouldn't get delivered, though, given SigBlk.

Yes, the SIGCHLD is pending and is blocked too. When restore starts CRIU,
before forking the root, blocks all signals but sigchild (criu_signals_setup).
Maybe SIGCHILD was blocked _before_ CRIU started and this block got inherited?

-- Pavel