[PVFS-users] Re: PVFS Hangups during concurrent reads/writes

[Rob Ross]

Hi Brannen,

I did a quick search and couldn't find any mention of 2.4.20 select() 
problems.  Of couse I would like this to be a kernel problem, or perhaps a 
libc problem, but I don't see anything indicating that others have had the 
same issues.

At the same time, no, we haven't had anything like this reported either!  
It's particularly odd to me that things work fine when on different 
machines while working just fine on the same machine!  Usually it is the 
other way around :).

Your test program is a little odd in that it moves back and forth between 
using the kernel and using the user library (if my cursory skim got the 
right impression).  Also, you're playing a dangerous game keeping extra 
copies of the PVFS headers in the test subdirectory; there are changes 
between what I see in there and CVS for sure.

Have you tried just using the kernel interface or just using the library?  
If so, did those work ok?  Do you have an /etc/pvfstab file set up on your 
machine pointing exactly to the same directory as the mount point?

Can you verify for me that PVFS_USE_NODELAY is defined in pvfs/config.h 
(not pvfs-kernel)?  It's probably defined twice (it's ok).

Thanks, and sorry we don't have a quick solution for you!

Rob


On Mon, 9 Aug 2004, Brannen S Hough wrote:

>              I've been trying to isolate this problem and find a way around
> it.  At its core it seems to be a select() call problem, which would mean a
> linux kernel problem.   Attached is a screen shot of the trace from running
> ddd on pvfsd, gets hung up on line 199 in sockset.c, which is calling
> dfd_select() (in pvfs-1.6.3-pre3/shared/dfd_set.c), which is calling
> select().  
> 
>              I tried updating my RedHat 9 to kernel version 2.4.20-31.9,
> recompiling everything, and rerunning my tests, but I got the same results.
> Any other ideas?   I could try rewriting the dfd_select routine to break out
> each socket file descriptor individually and calling select() on each
> instead of passing the array of file descriptors to select(), but I'm not
> sure that would fix the problem (and would make things slightly less
> efficient).