Re: [Libevent-users] [2.0.19-stable] Infinite loop

[sahil aggarwal <sahil.agg15@xxxxxxxxx>]

Azat,

Yes this happens every time server close the connection. To reproduce i :
* start my client (multiple threads but event_base being exclusive to
1 thread handling the events)
* start server
* generate some requests from client which succeed
* stop server
* generate some requests where now it loops forever.

I can write reproducer and try it with latest libevent too. In the
mean time i have live GDB attached, if you need any info let me know.

Thanks

On 14 September 2016 at 16:37, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
> On Wed, Sep 14, 2016 at 04:33:41PM +0530, sahil aggarwal wrote:
>> Hi,
>>
>> Getting stuck in infinite loop after retry on evhttp_connection. After
>> attaching GDB this is what i found:
>>
>> ----------
>>
>> #0  0x00007f9a8f5efdb9 in event_queue_remove (base=base@entry=0x24bf830,
>> ev=ev@entry=0x7f9a84006da0, queue=queue@entry=8)
>>     at event.c:2495
>> #1  0x00007f9a8f5f4040 in event_del_internal (ev=0x7f9a84006da0) at
>> event.c:2234
>> #2  timeout_process (base=0x24bf830) at event.c:2481
>> #3  event_base_loop (base=base@entry=0x24bf830, flags=flags@entry=0) at
>> event.c:1614
>>
>>
>> ---------
>>
>> #0  event_active_nolock (ev=<optimized out>, res=<optimized out>,
>> ncalls=<optimized out>) at event.c:2315
>> #1  0x00007f9a8f5f3f76 in timeout_process (base=0x24bf830) at event.c:2485
>> #2  event_base_loop (base=base@entry=0x24bf830, flags=flags@entry=0) at
>> event.c:1614
>>
>>
>> So the event is getting removed and queued in active queue. And event given
>> by
>>
>> ev = min_heap_top(&base->timeheap)
>>
>> doesn't have EV_TIMEOUT flag set due which it won't remove from the
>> min_heap and it always get the same event on the top hence the infinite
>> loop.
>>
>> * event_base not being shared across multiple threads.
>>
>> * How 1 have event in min_heap without EV_TIMEOUT  flag set and
>> e->ev_timeout_pos.min_heap_idx = -1  as on adding we always set the flag ?
>
> Hi,
>
> Does it triggers every time? If so can you please try libevent from
> sources (https://github.com/libevent/libevent)? And does you program
> single-threaded or multi?
>
> Also if you have a reproducer (~100 lines) it will be useful to see it.
>
> Thanks,
> Azat.
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