Re: Random segmentation fault

[John Dunlap]

I'll probably deal with this by staying on Debian 7 for the near future.
I'll attempt upgrading again in Debian 9.

On Mon, Sep 14, 2015 at 10:27 AM, Michael Schout  wrote:

> On 9/11/15 2:26 PM, John Dunlap wrote:
> > I found a lot of stuff like the following in my Apache logs. Is it
> > possible to get this kind of output from Apache when the server runs
> > out of memory? I wouldn't have expected so. It has all the hallmarks
> > of something more sinister.
>
> For whatever its worth, I started seen random segfaults starting between
> 5.18 and 5.20 somewhere.  I actually have a bizarre way to reproduce the
> one I see reliably by moving a return in my code.  I'm not sure if mine
> is related to the segfault you are seeing, but you might try downgrading
> to 5.18 if that is an option and see if the problem goes away.
>
> I'm stuck on 5.16 until I can figure this out because regexes have nasty
> bugs in 5.18 (see https://rt.perl.org/Public/Bug/Display.html?id=125491).
>
> I am planning to bisect against perl 5.19 git to figure out where this
> broke, but I just haven't had time yet.
>
> Regards,
> Michael Schout
>
>
>


-- 
John Dunlap
*CTO | Lariat *

*Direct:*
*j...@lariat.co *

*Customer Service:*
877.268.6667
supp...@lariat.co

Re: Random segmentation fault

[Michael Schout]

On 9/11/15 2:26 PM, John Dunlap wrote:
> I found a lot of stuff like the following in my Apache logs. Is it
> possible to get this kind of output from Apache when the server runs
> out of memory? I wouldn't have expected so. It has all the hallmarks
> of something more sinister.

For whatever its worth, I started seen random segfaults starting between
5.18 and 5.20 somewhere.  I actually have a bizarre way to reproduce the
one I see reliably by moving a return in my code.  I'm not sure if mine
is related to the segfault you are seeing, but you might try downgrading
to 5.18 if that is an option and see if the problem goes away.

I'm stuck on 5.16 until I can figure this out because regexes have nasty
bugs in 5.18 (see https://rt.perl.org/Public/Bug/Display.html?id=125491).

I am planning to bisect against perl 5.19 git to figure out where this
broke, but I just haven't had time yet.

Regards,
Michael Schout

Re: Random segmentation fault

[John Dunlap]

No, I have not. I don't have time to mess with compiling my own version and
I certainly don't have time to support a custom version. I always run the
version that comes with Debian out of the box.

On Mon, Sep 14, 2015 at 1:12 PM, Steve Hay 
wrote:

> Have you tried 5.20.3? This has just been released and contains a number
> of crash fixes. (I wonder if #123398 might be relevant?)
>
> On 14 September 2015 at 15:57, John Dunlap  wrote:
>
>> I'll probably deal with this by staying on Debian 7 for the near future.
>> I'll attempt upgrading again in Debian 9.
>>
>> On Mon, Sep 14, 2015 at 10:27 AM, Michael Schout  wrote:
>>
>>> On 9/11/15 2:26 PM, John Dunlap wrote:
>>> > I found a lot of stuff like the following in my Apache logs. Is it
>>> > possible to get this kind of output from Apache when the server runs
>>> > out of memory? I wouldn't have expected so. It has all the hallmarks
>>> > of something more sinister.
>>>
>>> For whatever its worth, I started seen random segfaults starting between
>>> 5.18 and 5.20 somewhere.  I actually have a bizarre way to reproduce the
>>> one I see reliably by moving a return in my code.  I'm not sure if mine
>>> is related to the segfault you are seeing, but you might try downgrading
>>> to 5.18 if that is an option and see if the problem goes away.
>>>
>>> I'm stuck on 5.16 until I can figure this out because regexes have nasty
>>> bugs in 5.18 (see https://rt.perl.org/Public/Bug/Display.html?id=125491
>>> ).
>>>
>>> I am planning to bisect against perl 5.19 git to figure out where this
>>> broke, but I just haven't had time yet.
>>>
>>> Regards,
>>> Michael Schout
>>>
>>>
>>>
>>
>>
>> --
>> John Dunlap
>> *CTO | Lariat *
>>
>> *Direct:*
>> *j...@lariat.co *
>>
>> *Customer Service:*
>> 877.268.6667
>> supp...@lariat.co
>>
>
>


-- 
John Dunlap
*CTO | Lariat *

*Direct:*
*j...@lariat.co *

*Customer Service:*
877.268.6667
supp...@lariat.co

Re: Random segmentation fault

[Steve Hay]

Have you tried 5.20.3? This has just been released and contains a number of
crash fixes. (I wonder if #123398 might be relevant?)

On 14 September 2015 at 15:57, John Dunlap  wrote:

> I'll probably deal with this by staying on Debian 7 for the near future.
> I'll attempt upgrading again in Debian 9.
>
> On Mon, Sep 14, 2015 at 10:27 AM, Michael Schout  wrote:
>
>> On 9/11/15 2:26 PM, John Dunlap wrote:
>> > I found a lot of stuff like the following in my Apache logs. Is it
>> > possible to get this kind of output from Apache when the server runs
>> > out of memory? I wouldn't have expected so. It has all the hallmarks
>> > of something more sinister.
>>
>> For whatever its worth, I started seen random segfaults starting between
>> 5.18 and 5.20 somewhere.  I actually have a bizarre way to reproduce the
>> one I see reliably by moving a return in my code.  I'm not sure if mine
>> is related to the segfault you are seeing, but you might try downgrading
>> to 5.18 if that is an option and see if the problem goes away.
>>
>> I'm stuck on 5.16 until I can figure this out because regexes have nasty
>> bugs in 5.18 (see https://rt.perl.org/Public/Bug/Display.html?id=125491).
>>
>> I am planning to bisect against perl 5.19 git to figure out where this
>> broke, but I just haven't had time yet.
>>
>> Regards,
>> Michael Schout
>>
>>
>>
>
>
> --
> John Dunlap
> *CTO | Lariat *
>
> *Direct:*
> *j...@lariat.co *
>
> *Customer Service:*
> 877.268.6667
> supp...@lariat.co
>

Re: Random segmentation fault

[Michael Schout]

On 9/14/15 12:12 PM, Steve Hay wrote:
> Have you tried 5.20.3? This has just been released and contains a
> number of crash fixes. (I wonder if #123398 might be relevant?)
I just tried 5.20.3.

For my issue (mentioned earlier in this thread), 5.20.3 does not help.

I'll post a followup message in  anew thread when I have time, but
basically, I started seeing two different problems somewhere between
5.19.0 and and 5.20.0:

1) "panic: attempt to copy freed scalar  to " reliably
reproduced when calling $cgi->param(x => ''); inside a TryCatch try { }
block. (and $cgi is CGI.pm here)

   Test case I have works perfectly against perl, but produces the above
panic under mod_perl.

  Seems to be something to do with TryCatch or Devel::Declare as the
problem goes away if I use eval { } instead of try { }.  Unfortunately
this is a large client codebase heavly invested in TryCatch so moving
away from that is not going to be fun/easy.

2) repeatable segfault by a certain subroutine doing something as simple as:

  sub foo {
my ($self, $field, $type) = @_;

if ($type = 'X') {
 return $self->_bar($field);
}
  }

  The fun part of this one is that if I remove the "return" keyword, the
segfault goes away.

Regards,
Michael Schout