Re: Thank you for trying out SWISH - here are the bugs

Hi again Jan,

Here's a goal that triggers a failed assertion:

?- thread_create((repeat, fail), Id, [detached(true)]),
thread_create(thread_get_message(Id, A),_,[]), thread_signal(Id,
abort).

Hope that can be fixed!

Best,
Torbjörn

On Sat, Jul 20, 2013 at 9:42 AM, Jan Wielemaker <[email protected]> wrote:
> Hi Torbjörn,
>
> Good to see it attracts attention!
>
> Destroying message queues is supposed to be safe at all times.  This
> is a bug.  Only, I need something to reproduce it, or at least a core
> dump in which I can poke around to examine the state of the system.
>
> (to do that, compile for debugging as indicated in build, enable core
> dumps using "ulimit -c unlimited" and provide me with a login).
>
>         --- Jan
>
> On 07/20/2013 09:36 AM, Torbjörn Lager wrote:
>> Hi All,
>>
>> Thanks to all of you who played with SWISH. The test release went well
>> I think, since only two bugs unknown to me has surfaced so far.
>> Norbert Fuchs found that when saving a program containing "\+" the
>> +-sign disappeared. Likely an encoding issue. Will fix it tomorrow or
>> on Monday.
>>
>> A more serios bug is related to the ending of sessions. Three times
>> last night the server crashed with the following message:
>>
>> [Thread 19] pl-thread.c:2899: destroy_message_queue: Assertion failed:
>> !queue->waiting && !queue->wait_for_drain
>> Stack trace labeled "crash":
>>   [0] swipl() [0x80eea93]
>>   [1] swipl() [0x80bcf0a]
>>   [2] swipl() [0x80bf0df]
>>   [3] swipl() [0x80c0b57]
>>   [4] swipl() [0x80c1d4b]
>>   [5] /lib/i686/cmov/libpthread.so.0(+0x5955) [0xb763b955]
>>   [6] /lib/i686/cmov/libc.so.6(clone+0x5e) [0xb75bbe7e]
>> Aborted
>>
>> I *think* that this occured when a session timed out (after ten
>> minutes of inactivity) and was supposed to clean up a few resources.
>> The relevant code is here:
>>
>> %   When a client session ends, the currently running goal (if any)
>> %   is aborted, the output queue is destroyed, and the client module
>> %   is emptied.
>>
>> :- listen(http_session(end(SessionId, _Peer)), end_session(SessionId)).
>>
>> end_session(SessionId) :-
>>     catch(thread_signal(SessionId, abort), _, true),
>>     atom_concat(SessionId, '.out', Output),
>>     message_queue_destroy(Output),
>>     forall(current_predicate(SessionId:PI),
>>         (   memberchk(PI, [read/1, write/1, writeln/1, nl/0])
>>         ->  true
>>         ;   abolish(SessionId:PI)
>>         )
>>     ).
>>
>> The message queue is created when the session begins and as far as I
>> can see it should be possible to destroy it in this way. Maybe you can
>> spot the problem?
>>
>> I will have to return to this on Monday. I will leave the server
>> running, but I guess it is likely to crash again and then I won't be
>> here to restart it.
>>
>> Best,
>> Torbjörn
>>
>> --
>> Torbjörn Lager
>> Professor of General and Computational Linguistics
>> Department of Philosophy, Linguistics and Theory of Science
>> University of Gothenburg
>> Box 200, SE-405 30 Gothenburg, Sweden
>> Phone: +46317864962
>> _______________________________________________
>> SWI-Prolog mailing list
>> [email protected]
>> https://lists.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
>>



-- 
Torbjörn Lager
Professor of General and Computational Linguistics
Department of Philosophy, Linguistics and Theory of Science
University of Gothenburg
Box 200, SE-405 30 Gothenburg, Sweden
Phone: +46317864962