[openib-general] RFC: deadlock in uverbs_cmd.c

[Michael S. Tsirkin]

Hello!

uverbs_cmd currently locks both send and receive cq with down_write during
ib_uverbs_create_qp operation.

It seems that it is easy to create a deadlock here by creating 2 QPs:

QP1 - send completions go to CQ1, receive completions go to CQ2
QP2 - send completions go to CQ2, receive completions go to CQ1

Comments?
Further, Roland, would you mind writing up something about the
lock nesting in uverbs?

-- 
MST