Re: [LTP] [PATCH] pthread_detach/4-3: workaround for segment fault

[Kang Kai <Kai.Kang@windriver.com>]

On 2012年08月23日 19:07, Jan Stancek wrote:
> On 08/23/2012 09:09 AM, Jan Stancek wrote:
>>
>> ----- Original Message -----
>>> From: "Kang Kai"<Kai.Kang@windriver.com>
>>> To: "Jan Stancek"<jstancek@redhat.com>, gaowanlong@cn.fujitsu.com
>>> Cc: ltp-list@lists.sourceforge.net, "Zhenfeng Zhao"<Zhenfeng.Zhao@windriver.com>
>>> Sent: Thursday, 23 August, 2012 8:21:43 AM
>>> Subject: Re: [LTP] [PATCH] pthread_detach/4-3: workaround for segment fault
>>>
>>> On 2012年08月22日 22:20, Jan Stancek wrote:
>>>> On 08/22/2012 10:58 AM, Jan Stancek wrote:
>>>>> ----- Original Message -----
>>>>>> From: "Kang Kai"<Kai.Kang@windriver.com>
>>>>>> To: "Jan Stancek"<jstancek@redhat.com>
>>>>>> Cc: gaowanlong@cn.fujitsu.com, ltp-list@lists.sourceforge.net,
>>>>>> "Zhenfeng Zhao"<Zhenfeng.Zhao@windriver.com>
>>>>>> Sent: Wednesday, 22 August, 2012 10:28:59 AM
>>>>>> Subject: Re: [LTP] [PATCH] pthread_detach/4-3: workaround for
>>>>>> segment fault
>>>>>> Hi Jan,
>>>>>>
>>>>>>> Is the above output from mips or x86_64?
>>>>>>> Are you running it as root user?
>>>>>> This was tested on x86_64 with unprivileged  user. I retest it
>>>>>> with
>>>>>> root
>>>>>> and test passes.
>>>>> Your unprivileged user is hitting some resource limit, I'd be
>>>>> interested
>>>>> to see how many threads are actually running at the same time.
>>>>>
>>>>>> It passes on routerstation(mips) with your patch too.
>>>>>> So it looks like a race condition issue about stack attribute
>>>>>> between
>>>>>> threads, right?
>>>>> I think so. We can try different way of signalling when threaded()
>>>>> is done
>>>>> and try it again with all scenarios.
>>>> I think this testcase is broken in more than 1 way. At least on my
>>>> setup, I don't see
>>>> a single pthread_detach() while signals are firing - which is
>>>> exactly goal of this test.
>>>>
>>>> With following change:
>>>>
>>>> diff --git
>>>> a/testcases/open_posix_testsuite/conformance/interfaces/pthread_detach/4-3.c
>>>> b/testcases/open_posix_testsuite/conforman
>>>> index dfa6e19..48e1343 100644
>>>> ---
>>>> a/testcases/open_posix_testsuite/conformance/interfaces/pthread_detach/4-3.c
>>>> +++
>>>> b/testcases/open_posix_testsuite/conformance/interfaces/pthread_detach/4-3.c
>>>> @@ -277,6 +276,7 @@ int main(int argc, char *argv[])
>>>>                   do_it1 = 0;
>>>>           } while (do_it1);
>>>>
>>>> +       output("  %d thread detached while signals were firing.\n",
>>>> count_ope);
>>>>           sleep(1);
>>>>
>>>>           do {
>>>>
>>>> I get:
>>>> [16:11:23]  1 thread detached while signals are firing.
>>>> [16:11:24]Test executed successfully.
>>>> [16:11:24]  77865 thread detached.
>>>>
>>>> and that reported "1" is how many threads attempted to call
>>>> pthread_detach, not how many actually
>>>> succeeded. Signals are firing so frequently that threaded() can't
>>>> progress at all.
>>> Then how do we fix this case? sync sending the signals with
>>> pthread_detach?
>> I was thinking usleep(sleep_time) that progressively increases. So it
>> starts firing signals as quickly as it can and slows down over time.
>> Each pthread_detach() would reset the sleep_time.
>>
>> As for our original issue, idea I'm playing with is:
>>
>> main (procA) - do_child (procB) - send_sig (thread)
>>                                  \
>>                                    test (thread) - threaded (detached thread)
>>
>> - turn 'while' in test() to single 'for' loop
>> - loop in main, fork and call do_child, wait for child to finish
> Hi,
>
> attached is v1 of the idea above. I ran it 100x times on various
> setups as root and unprivileged user.

Hi Jan,

Great!
> Kai, would you like to give a try?
I have test it on routerstation, x86_64(ubuntu11.10 & redhat 5.3) and 
x86(redhat 5.3) each 100+ times, and all PASS.

Regards,
Kai

>
> Regards,
> Jan
>
>> This way we can be sure, that we don't reuse same stack for multiple threads,
>> and we can also be sure, there won't be more than NSCENAR threads, so unprivileged
>> user should not run out of resources.
>>
>> Regards,
>> Jan
>>
>>> Wanlong, any comments?
>>>
>>> Thanks,
>>> Kai
>>>
>>>> Regards,
>>>> Jan
>>>>
>>>
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