kern/37436: [hang] accept dead loop when out of file descriptors

[Jin Guojun]

Kip Macy wrote:

>On Nov 16, 2007 5:34 PM, Jin Guojun <jin at george.lbl.gov> wrote:
>  
>
>>kmacy at FreeBSD.org wrote:
>>
>>    
>>
>>>Synopsis: [hang] accept dead loop when out of file descriptors
>>>
>>>State-Changed-From-To: open->feedback
>>>State-Changed-By: kmacy
>>>State-Changed-When: Sat Nov 17 01:19:37 UTC 2007
>>>State-Changed-Why:
>>>
>>>Is this still an issue?
>>>
>>>http://www.freebsd.org/cgi/query-pr.cgi?pr=37436
>>>
>>>
>>>      
>>>
>>I will check into it in a week.
>>    
>>
>
>By "still", I mean RELENG_6 or better yet RELENG_7.
>
> -Kip
>  
>
Another slightly odd thing is discovered during repeat this test.
The maximum number of threads (pthread_create via libthr) can be created 
is 111.
Therefore, there is no way to reproduce this problem due to 
pthread_create problem.

The pthread_create() fails due to Error<35> Resource temporarily 
unavailable. However,
memory allocation is still functioning. I have tested on a 256MB laptop 
and a 1GB desktop,
both had the same problem for pthread creation -- maximum 111 threads 
can be created.
Below is my resource limits and I do not believe that is the problem:

/home/users/libthr: limit
cputime      unlimited
filesize     unlimited
datasize     1048028 kbytes
stacksize    65536 kbytes
coredumpsize unlimited
memoryuse    unlimited
vmemoryuse   unlimited
descriptors  11095
memorylocked unlimited
maxproc      5547
sbsize       unlimited

It looks like 6.2-R and RELENG_6/7 kernel has some restriction on number 
of threads to handle,
because all libthr, libpthread and libc_r all behave the same.
Is this true?

So, that only test can be done is to set descriptors limit to 117 on the 
server to test 111
connections from a client. Such test is Ok.
If the descriptors limit is set to 116, the accept will return error 
without hanging.
But I do not know if this will be true when the number of descriptors 
used is larger.

I tried to run the same command multiple times on the same client, it 
does not help much.
I will look this issue further.

-Jin