[Pvfs2-developers] Odd problem

Pete Wyckoff pw at padd.com
Wed Jul 15 16:33:06 EDT 2009


walt at clemson.edu wrote on Wed, 15 Jul 2009 16:09 -0400:
> whilst working with a branch (not the trunk) I came upon an odd bug.  
> During server initialization in the function lebf_initialize() the  
> function creates a dummy request and encodes it over and over again,  
> once for each request type in order to discover the max size.  This  
> dummy request is never zero'd between iterations.  I found that in some  
> instances this caused a seg fault - but changing almost anything might  
> undo it.  Same code compiled/linked a different way may or may not fail.  
>  Simply putting a memset() in the loop fixes it, as far as I can tell.
>
> Anyone know why we don't zero the request, or object to adding that?  
> Seems to have no performance impact since it is in initialization.

I toyed around with this code almost six years ago.  The idea at the
time was that the switch in lebf_initialize set just the right
parameters needed by the various encode_PVFS_servreq_....  handlers.
Although now that you mention it, setting everything back to zero
does make sense, in that things generally behave nicely when
presented with zeroes.

Since this code has in the past failed to make valgrind complain, I
do have to wonder if you forgot to initialize some fields needed for
your new request type.  But a memset() in that loop would be pretty
harmless if it fixes things for you; it only happens once at
client/server startup.

		-- Pete


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