Re: [LTP] [PATCH] Synchronization between two processes

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Wei Yongjun (yjwei@cn.fujitsu.com):
> Serge E. Hallyn wrote:
>> Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
>>   
>>> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote:     
>>>> Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
>>>>       
>>>>> The child-process wait SIGUSR1 which would be sended by parent-process,
>>>>> if the child-process execute sigtimedwait() after parent-process 
>>>>> send the signal, it would never receive the SIGUSR1 from 
>>>>> parent-process.
>>>>> I cann't make sure the SIGUSR1 be sended after child-process 
>>>>> execute sigtimedwait() with 100 percent, and i try my best.
>>>>>         
>>>> Well, in theory I suppose this could happen, but you'd have to have
>>>> a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
>>>> between the pipe read and signal send, while the child goes straight
>>>> from pipe write to sigtimedwait.
>>>>
>>>> Have you seen this signal be missed?  If not, then I'd rather assume
>>>> things are reasonable.  If you have seen this happen, then why not
>>>> instead set up a SIGUSR1 handler in the child before doing the pipe
>>>> write, then just sleep for 3 seconds instead of doing sigtimedwait?
>>>>       
>>> Thanks Serge.
>>>     
>>
>> Or, if I'm being unreasonable, then at least have the parent only wait
>> for at most 1 second, and leave the child alone.  Every every ltp test
>> is going to hang for 5 seconds...
>>
>> But I prefer setting the signal handler ahead of time.
>>
>>   
> Sorry to relpy late.
>
> As your last advice, i change the test case, and it work will.
>
> [PATCH] fix sync problem between two processes of pidns12 test
>
> The child-process wait SIGUSR1 which would be sended by parent-process,
> if the child-process execute sigtimedwait() after parent-process send
> the signal, it would never receive the SIGUSR1 from parent-process.
>
> This patch rewrite child_signal_handler() to handle to SIGUSR1 and
> instead sigtimedwait() with sleep for 3 seconds.

Thank you, this looks right.

I assume the reason it wasn't originally done this way, was out of
a concern that the TPASS/TFAIL out of signal handler wouldn't
count...

-serge

------------------------------------------------------------------------------
Register Now for Creativity and Technology (CaT), June 3rd, NYC. CaT
is a gathering of tech-side developers & brand creativity professionals. Meet
the minds behind Google Creative Lab, Visual Complexity, Processing, & 
iPhoneDevCamp asthey present alongside digital heavyweights like Barbarian
Group, R/GA, & Big Spaceship. http://www.creativitycat.com 
_______________________________________________
Ltp-list mailing list
Ltp-list@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/ltp-list