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Subject: Re: [OMPI devel] openib unloaded before last mem dereg
From: Steve Wise (swise_at_[hidden])
Date: 2013-01-28 15:46:26


On 1/28/2013 2:04 PM, Ralph Castain wrote:
> On Jan 28, 2013, at 11:55 AM, Steve Wise <swise_at_[hidden]> wrote:
>
>> Do you know if the rdmacm CPC is really being used for your connection setup (vs other CPCs supported by IB)? Cuz iwarp only supports rdmacm. Maybe that's the difference?
> Dunno for certain, but I expect it is using the OOB cm since I didn't direct it to do anything different. Like I said, I suspect the problem is that the cluster doesn't have iWARP on it.

Definitely, or it could be the different CPC used for IWvs IB is
tickling the issue.

>> Steve.
>>
>> On 1/28/2013 1:47 PM, Ralph Castain wrote:
>>> Nope - still works just fine. I didn't receive that warning at all, and it ran to completion without problem.
>>>
>>> I suspect the problem is that the system I can use just isn't configured like yours, and so I can't trigger the problem. Afraid I can't be of help after all... :-(
>>>
>>>
>>> On Jan 28, 2013, at 11:25 AM, Steve Wise <swise_at_[hidden]> wrote:
>>>
>>>> On 1/28/2013 12:48 PM, Ralph Castain wrote:
>>>>> Hmmm...afraid I cannot replicate this using the current state of the 1.6 branch (which is the 1.6.4rcN) on the only IB-based cluster I can access.
>>>>>
>>>>> Can you try it with a 1.6.4 tarball and see if you still see the problem? Could be someone already fixed it.
>>>> I still hit it on 1.6.4rc2.
>>>>
>>>> Note iWARP != IB so you may not have this issue on IB systems for various reasons. Did you use the same mpirun line? Namely using this:
>>>>
>>>> --mca btl_openib_ipaddr_include "192.168.170.0/24"
>>>>
>>>> (adjusted to your network config).
>>>>
>>>> Because if I don't use ipaddr_include, then I don't see this issue on my setup.
>>>>
>>>> Also, did you see these logged:
>>>>
>>>> Right after starting the job:
>>>>
>>>> --------------------------------------------------------------------------
>>>> No OpenFabrics connection schemes reported that they were able to be
>>>> used on a specific port. As such, the openib BTL (OpenFabrics
>>>> support) will be disabled for this port.
>>>>
>>>> Local host: hpc-hn1.ogc.int
>>>> Local device: cxgb4_0
>>>> Local port: 2
>>>> CPCs attempted: oob, xoob, rdmacm
>>>> --------------------------------------------------------------------------
>>>> ...
>>>>
>>>> At the end of the job:
>>>>
>>>> [hpc-hn1.ogc.int:07850] 5 more processes have sent help message help-mpi-btl-openib-cpc-base.txt / no cpcs for port
>>>>
>>>>
>>>> I think these are benign, but prolly indicate a bug: the mpirun is restricting the job to use port 1 only, so the CPCs shouldn't be attempting port 2...
>>>>
>>>> Steve.
>>>>
>>>>
>>>>> On Jan 28, 2013, at 10:03 AM, Steve Wise <swise_at_[hidden]> wrote:
>>>>>
>>>>>> On 1/28/2013 11:48 AM, Ralph Castain wrote:
>>>>>>> On Jan 28, 2013, at 9:12 AM, Steve Wise <swise_at_[hidden]> wrote:
>>>>>>>
>>>>>>>> On 1/25/2013 12:19 PM, Steve Wise wrote:
>>>>>>>>> Hello,
>>>>>>>>>
>>>>>>>>> I'm tracking an issue I see in openmpi-1.6.3. Running this command on my chelsio iwarp/rdma setup causes a seg fault every time:
>>>>>>>>>
>>>>>>>>> /usr/mpi/gcc/openmpi-1.6.3-dbg/bin/mpirun --np 2 --host hpc-hn1,hpc-cn2 --mca btl openib,sm,self --mca btl_openib_ipaddr_include "192.168.170.0/24" /usr/mpi/gcc/openmpi-1.6.3/tests/IMB-3.2/IMB-MPI1 pingpong
>>>>>>>>>
>>>>>>>>> The segfault is during finalization, and I've debugged this to the point were I see a call to dereg_mem() after the openib blt is unloaded via dlclose(). dereg_mem() dereferences a function pointer to call the btl-specific dereg function, in this case it is openib_dereg_mr(). However, since that btl has already been unloaded, the deref causes a seg fault. Happens every time with the above mpi job.
>>>>>>>>>
>>>>>>>>> Now, I tried this same experiment with openmpi-1.7rc6 and I don't see the seg fault, and I don't see a call to dereg_mem() after the openib btl is unloaded. That's all well good. :) But I'd like to get this fix pushed into 1.6 since that is the current stable release.
>>>>>>>>>
>>>>>>>>> Question: Can someone point me to the fix in 1.7?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> Steve.
>>>>>>>> It appears that in ompi_mpi_finalize(), mca_pml_base_close() is called which unloads the openib btl. Then further down in ompi_mpi_finalize(), mca_mpool_base_close() is called which ends up calling dereg_mem() which seg faults trying to call into the unloaded openib btl.
>>>>>>>>
>>>>>>> That definitely sounds like a bug
>>>>>>>
>>>>>>>> Anybody have thoughts? Anybody care? :)
>>>>>>> I care! It needs to be fixed - I'll take a look. Probably something that forgot to be cmr'd.
>>>>>> Great! If you want me to try out a fix or gather more debug, just hollar.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Steve.
>>>>>>