[Pvfs2-developers] Re: pointer aliasing and interface->set_info semantics

[Scott Atchley]

On Mar 4, 2008, at 6:58 PM, Pete Wyckoff wrote:

> troy at scl.ameslab.gov wrote on Tue, 04 Mar 2008 17:35 -0600:
>> It looks like the IB BMI layer is ending up double-freeing the  
>> method_addr
>> structure on the BMI_ib_set_info function, but it only happens  
>> when the
>> Metadata server is also a data server.
>>
>> If you look at the following GDB output, the last two entries have  
>> the same
>> method_addr, and I can't figure out a good way to tell in  
>> BMI_set_info if
>> the method_address has already been freed. It also looks like the  
>> id_string
>> has been mangled or freed somewhere earlier as well.
>
> All your deadref were different values there, so I'm not seeing the
> double-free aspect.  But I have no doubt that you're on to something
> in here.  Also, at this location, the id_string and method_addr have
> already been freed, so we shouldn't count on them having reasonable
> values in them.
>
> I've always had a hard time keeping these references straight.  Can
> you verify that you're getting to these spots via dealloc_ref_st(),
> and maybe a couple steps up from there, for sanity?
>
> Trying to figure out what other devices do in the DROP_ADDR handler.
> MX goes and calls bmi_method_addr_forget_callback() in there, but
> that doesn't seem right, as it will just wind around through
> dealloc_ref_st() again.  It looks like TCP is doing more or less
> what IB is doing.

Pete,

I do not see where bmi_ib uses bmi_method_addr_forget_callback() at  
all. I am looking at the tcp code and I do need to fix how/where I  
use the above.

Scott