Re: ib_destroy_cm_id() versus cm callback race ?

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 04/27/12 17:18, Hefty, Sean wrote:

>> If I interpret the source code in drivers/infiniband/core/cm.c correctly
>> ib_destroy_cm_id() can return before an ongoing cm_id callback has
>> finished. Is this on purpose ? If not, isn't there a
>> flush_workqueue(cm.wq) call missing in cm_destroy_id() ?
> 
> ib_destroy_cm_id() will block while there's an outstanding reference

> held on the id.  We'll hold a reference on an id if we have any MAD
> outstanding against it (which can result in a send callback) or
> during the processing of a receive.

Hello Sean,

Thanks for the quick reply. Something else: I've noticed that the IB CM
work queue is created as follows:

    cm.wq = create_workqueue("ib_cm");

That makes me wonder how it is prevented that two CM callbacks for the
same CM ID run concurrently on different CPUs ?

Thanks,

Bart.
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