[openib-general] oops with multicast patches

[dotanb at dev.mellanox.co.il]

>  > Roland is right: this test only attaches QPs to the mcg using verbs
> call
>  > (ibv_attach_mcast).
>
> What I don't understand is why the test has any affect on the kernel
> at all.  How could creating QPs and attaching them to MCGs with verbs
> calls cause the crash??

Everytime that the IPoIB finds out that there is a new SM (using the
client reregister or LID change event), it try to join several (3-4) mcgs.

The user level application uses almost all of the multicast groups in the
machine. Only 1,2,3,4 mcgs (depends on the test case) are available for
the IPoIB to use: it start to attach (and maybe join) all the mcgs that it
needs and fails when it reaches the HCA mcgs limit.

Maybe there is a problem with the multicast module when the attach to
multicast group verb fails?

Dotan