[Libevent-users] Infinite loop in event_process_active()

[nicolas dumont]

Hi,

I'm using events in 1.4.12-stable.

Sometimes, my daemon, which uses event_base_loop()
goes in an infinite loop ( verbose traces below ).

This infinite loop is inside function event_process_active() which
calls event_del() with ev_flags=0x80 ( =EVLIST_INIT)
This flags is not managed by event_del(), then the ev is never deleted
from the queue, then the loop "for" retries again and again.

static void event_process_active(struct event_base *base)
{
...
     for (ev = TAILQ_FIRST(activeq); ev; ev = TAILQ_FIRST(activeq)) {
             if (ev->ev_events & EV_PERSIST)
                     event_queue_remove(base, ev, EVLIST_ACTIVE);
             else
                     event_del(ev);
...
   }
}


[2009-08-26 17:12:29] ev  : event_add: event: 0xb13a7e0, EV_READ
call 0x280b789c
[2009-08-26 17:12:29] ev  : kq_insert: fd 43 EVFILT_READ
[2009-08-26 17:12:29] ev  : event_queue_insert queue=0x2  ev_flags=0x1082
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x1082 ev_events 0x2
[2009-08-26 17:12:29] ev  : event_queue_remove queue=0x2  ev_flags=0x1080
[2009-08-26 17:12:29] ev  : kq_insert: fd 74 EVFILT_READ (del)
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x80 ev_events 0x2
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x80 ev_events 0x2
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x80 ev_events 0x2
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x80 ev_events 0x2
[2009-08-26 17:12:29] ev  : event_process_active: call event_del
[2009-08-26 17:12:29] ev  : event_del: 0xb13e6a0, callback 0x280b7dd4,
ev_flags 0x80 ev_events 0x2
.....
....
...
..
.

After investigating my code, I found that I call in this order :

event_set(&ev, EV_READ,callback_one);
event_add(&ev);

and later :
event_set(&ev, EV_READ,callback_two);


After that I fall into the infinite loop describe behind.



Finnaly, to prevent to go in the infinite loop ,
do I have to run event_del(&ev) each time before using event_set(&ev) ?

Thank's a lot for your answer.

Nicolas.

--
Nicolas Dumont
System development engineer

NETASQ - We secure IT
3 rue Archimede
59650 Villeneuve d'Ascq
France
Tel :  +33 (0)3.20.61.90.44

The pb is that the second event_set which is called to set another callback resets the ev->flags with EVLIST_INIT So, even if I'm doing something wrong with the usage of the API, it should not go in an infinite loop. Fax : +33 (0)3.20.61.97.48

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