"Got signal before environment was installed on our thread"

Mon Sep 11 23:13:16 UTC 2017

On Mon, Sep 4, 2017 at 11:15 AM, Daniel Kochmański <daniel at turtleware.eu> wrote:
> From the backtrace it is sure that fail is caused inside the call to
> GC_init. Such errors are known to have happened when another GC was
> initialized already on the system (I've linked the issue). It might be
> caused by something else in bdwgc, I don't know. Either way I'd focus on
> GC_init part.

Our project (sagemath) only uses libgc within the embedded ECL. Thus I
am really puzzled how another libgc instance might kick in and spoil
the game for ECL.

One possibility is that clang is using libgc, and thus, in principle,
libgc might be sitting somewhere in the runtime?!

>
> To make sure, that I'm right with my assertion you may put printf before and
> after call to GC_init. I'm not quite familiar with bdwgc internals to say,
> what is wrong though. Maybe updating bundled sources of GC will help? Or
> linking with libgc on the system? It might be that it was a bug in bdwgc
> which got already fixed.

We are not using the bdwgc shipped with ECL, we use a separate libgc
7.6.0, which is the latest stable.
(Is there a reason to ship bdwgc sources with ECL - do you patch it?)

Thanks,
Dima

>
> Regards,
>
> Daniel
>
>
>
> On 04.09.2017 12:04, Dima Pasechnik wrote:
>>
>> On Fri, Sep 1, 2017 at 1:57 PM, Daniel Kochmański <daniel at turtleware.eu>
>> wrote:
>>>
>>> I dont think its related to shared vs static - rather two gc running
>>> concurrently. Try commenting out GC_init call in ecl and see what
>>> happens.
>>
>> I don't understand how two GCs can run concurrently on a memory region
>> controlled by ECL which is statically linked to GC...
>> In fact I am pretty sure no other instances of GC are running anywhere
>> within our process tree.
>>
>> By the way, I don't know whether it's obvious from the backtrace that
>> cl_boot() has been completed, or not.
>>
>> If it actually was completed, could it be a bug that invalidates the
>> bit indicating that cl_boot() has been done?
>>
>> We have seen similar troubles with clang recently, related to FPE.
>> There an FPE bit was flipped by assignment of a double to an
>> integer type (sic!).
>> It took us a lot of head banging on various hard surfaces to debug this:
>> https://trac.sagemath.org/ticket/22799
>> it turned out we did hit a known bug:
>> https://bugs.llvm.org//show_bug.cgi?id=17686
>>
>>> Do you need sigchld for anything? Run-program was rewritten and sigchld
>>> handling wasnt viable option anymore for it.
>>>
>> We do set ECL_OPT_TRAP_SIGCHLD to 0, thus I presume we
>> now can simply skip it all together.
>>
>> Thanks,
>> Dima
>>
>>> Im on phone, will be avail after the weekend.
>>>
>>> Regards, D.
>>>
>>>
>>> Dnia 1 września 2017 14:47:57 CEST, Dima Pasechnik
>>> <dimpase+ecl at gmail.com>
>>> napisał(a):
>>>>
>>>> Hi Daniel,
>>>> Thanks for the message. The scenario you talk about only happens if GC
>>>> is a shared library, right?
>>>>
>>>> I've rebuilt GC disabling shared libs, and ECL doing static linking to
>>>> GC.
>>>> And I still get very similar segfaults:
>>>>
>>>> ;;; ECL C Backtrace
>>>> ;;;    0 ecl_internal_error (0x87d79b375)
>>>> ;;;    1 init_unixint (0x87d7c17e0)
>>>> ;;;    2 init_unixint (0x87d7c1582)
>>>> ;;;    3 pthread_sigmask (0x80103779d)
>>>> ;;;    4 pthread_getspecific (0x801036d6f)
>>>> ;;;    5 unknown (0x7ffffffff193)
>>>> ;;;    6 GC_push_current_stack (0x87d7ef7c3)
>>>> ;;;    7 GC_with_callee_saves_pushed (0x87d7f7360)
>>>> ;;;    8 GC_push_roots (0x87d7ef9c2)
>>>> ;;;    9 GC_mark_some (0x87d7ec97c)
>>>> ;;;   10 GC_stopped_mark (0x87d7e6b7a)
>>>> ;;;   11 GC_try_to_collect_inner (0x87d7e6a75)
>>>> ;;;   12 GC_init (0x87d7f08ea)
>>>> ;;;   13 init_alloc (0x87d7d5669)
>>>> ;;;   14 cl_boot (0x87d69f66b)
>>>> ...
>>>>
>>>> And a very similar picture on the develop branch of ECL - although
>>>> I had to change our code, as  in particular
>>>> ECL_OPT_TRAP_SIGCHLD is gone...
>>>>
>>>> So, what can it be? Some signals issue?
>>>>
>>>> Thanks,
>>>> Dima
>>>>
>>>> On Fri, Sep 1, 2017 at 7:38 AM, Daniel Kochmański <daniel at turtleware.eu>
>>>> wrote:
>>>>>
>>>>>   Hey Dima,
>>>>>
>>>>>   this looks like the issue with having GC initialized before ECL kicks
>>>>> in.
>>>>>   See https://gitlab.com/embeddable-common-lisp/ecl/issues/371 for a
>>>>>   discussion about this problem. Basically some other component already
>>>>> called
>>>>>   GC_init and ECL calls it once more. It's arguably not a bug.
>>>>>
>>>>>   Best regards,
>>>>>
>>>>>   Daniel
>>>>>
>>>>>
>>>>>   On 31.08.2017 15:29, Dima Pasechnik wrote:
>>>>>>
>>>>>>
>>>>>>   Dear all,
>>>>>>
>>>>>>   I'm struggling to understand strange segfaults coming from
>>>>>>   ECL(+Maxima) on FreeBSD embedded into Python; they typically look as
>>>>>>   follows:
>>>>>>
>>>>>>   Got signal before environment was installed on our thread
>>>>>>      [2: No such file or directory]
>>>>>>
>>>>>>   ;;; ECL C Backtrace
>>>>>>   ;;;    0 ecl_internal_error (0x87d790765)
>>>>>>   ;;;    1 init_unixint (0x87d7b6bd0)
>>>>>>   ;;;    2 init_unixint (0x87d7b6972)
>>>>>>   ;;;    3 pthread_sigmask (0x80103779d)
>>>>>>   ;;;    4 pthread_getspecific (0x801036d6f)
>>>>>>   ;;;    5 unknown (0x7ffffffff193)
>>>>>>   ;;;    6 GC_push_all_stacks (0x87db1ea2c)
>>>>>>   ;;;    7 GC_mark_some (0x87db12eec)
>>>>>>   ;;;    8 GC_stopped_mark (0x87db09baa)
>>>>>>   ;;;    9 GC_try_to_collect_inner (0x87db09a75)
>>>>>>   ;;;   10 GC_init (0x87db16f4f)
>>>>>>   ;;;   11 init_alloc (0x87d7caa59)
>>>>>>   ;;;   12 cl_boot (0x87d694a5b)
>>>>>>   ;;;   13 initecl (0x87d218340)
>>>>>>   ;;;   14 initecl (0x87d20a43f)
>>>>>>   ;;;   15 initecl (0x87d207e28)
>>>>>>   ;;;   16 _PyImport_LoadDynamicModule (0x800b3ed1c)
>>>>>>   ;;;   17 PyImport_AppendInittab (0x800b3d71f)
>>>>>>   ;;;   18 PyImport_AppendInittab (0x800b3d1a8)
>>>>>>   ;;;   19 PyImport_ImportModuleLevel (0x800b3c2ce)
>>>>>>   ;;;   20 _PyBuiltin_Init (0x800b162d7)
>>>>>>   ;;;   21 PyObject_Call (0x800a7d3e3)
>>>>>>   ;;;   22 PyEval_EvalFrameEx (0x800b2121c)
>>>>>>   ;;;   23 PyEval_EvalCodeEx (0x800b1b5d4)
>>>>>>   ;;;   24 PyEval_EvalCode (0x800b1ad96)
>>>>>>   ;;;   25 PyImport_ExecCodeModuleEx (0x800b3ad11)
>>>>>>   ;;;   26 PyImport_AppendInittab (0x800b3ddb8)
>>>>>>   ;;;   27 PyImport_AppendInittab (0x800b3d71f)
>>>>>>   ;;;   28 PyImport_AppendInittab (0x800b3d1a8)
>>>>>>   ;;;   29 PyImport_ImportModuleLevel (0x800b3c2ce)
>>>>>>   ;;;   30 _PyBuiltin_Init (0x800b162d7)
>>>>>>   ;;;   31 PyEval_EvalFrameEx (0x800b22dd1)
>>>>>>   Segmentation fault (core dumped)
>>>>>>
>>>>>>   It looks as if ECL (version 16.1.2) is being called before an
>>>>>>   initialisation is complete, but it it possible to say more without a
>>>>>>   debugger?
>>>>>>
>>>>>>   More details: is is on FreeBSD 11.0, clang 3.8.0, GC version 7.6.0
>>>>>>   with libatomic_ops version 7.4.6.
>>>>>>   And only reproducible on FreeBSD.
>>>>>>
>>>>>>   ECL is built with --disable-threads; GC is built with or without
>>>>>>   threads---result is still the same.
>>>>>>   (so it's unclear to me where pthread_* calls in the trace
>>>>>>   come from).
>>>>>>
>>>>>>   Thanks,
>>>>>>   Dima
>>>>>>
>>>>>>   PS. the segfault is at the bottom of
>>>>>>   https://trac.sagemath.org/ticket/22679#comment:87
>>>>>
>>>>>
>>>>>
>>> -- Wysłane za pomocą K-9 Mail.
>
>