On Fri, Jan 13, 2012 at 11:46 AM, Ralph Castain <[email protected]> wrote:
>> Adding some assertions in event_add_internal might track this down.
>> Trivially, you could do
>> if (tv && !tv_is_absolute) {
>> /* waiting one billion seconds should be enough for anyone */
>> EVUTIL_ASSERT(tv->tv_sec < 1000000000);
>> }
>>
>> to try to detect 1 and 2.
>
> Interesting. The above code never tripped, so I dug a little further and
> found that event_add_internal is never being called with a tv value that is
> large. I did find it to be a race condition - sometimes the code completes
> and exits before I get the error condition report.
>
> The timeout value clearly isn't a garbage value - I dumped the values out,
> compared to current time as of the error:
>
> warn] select: Invalid argument
> TV OUT OF SPEC AT CNT 2: value 1326472513:976848 curtime 1326472513:977043
> Ralph
> [warn] select: Invalid argument
> TV OUT OF SPEC AT CNT 3: value 1326472513:977327 curtime 1326472513:977413
>
> So the value is getting updated and appears valid. What's strange is why
> libevent is passing an absolute time to select as it is supposed to be a
> relative value per the man page:
Right.
[...]
> Any easy way I can output an identifier that would tell us something about
> which event is involved? I see that I'm not getting output from the
> event_debug calls in the code, even though I've configured with debug enabled
> and called:
>
> event_enable_debug_mode();
> event_set_debug_output(1);
>
> Anything else required to get that output? Would it help?
Maybe. I'd look at adding debugging logs or printfs to
event_base_loop and timeout_next() and timeout_correct(): Those are
the ones that determine the value of the timeout to be passed to
evsel->dispatch. The event that's getting the weird value is set by
ev = min_heap_top(&base->timeheap);
in timeout_next.
--
Nick
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