[PATCHv6 1/4] RDMA/rxe: Fix dead lock caused by __rxe_add_to_pool interrupted by rxe_pool_get_index

[yanjun.zhu@xxxxxxxxx]

From: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>

This is a dead lock problem.
The ah_pool xa_lock first is acquired in this:

{SOFTIRQ-ON-W} state was registered at:

  lock_acquire+0x1d2/0x5a0
  _raw_spin_lock+0x33/0x80
  __rxe_add_to_pool+0x183/0x230 [rdma_rxe]

Then ah_pool xa_lock is acquired in this:

{IN-SOFTIRQ-W}:

Call Trace:
 <TASK>
  dump_stack_lvl+0x44/0x57
  mark_lock.part.52.cold.79+0x3c/0x46
  __lock_acquire+0x1565/0x34a0
  lock_acquire+0x1d2/0x5a0
  _raw_spin_lock_irqsave+0x42/0x90
  rxe_pool_get_index+0x72/0x1d0 [rdma_rxe]
  rxe_get_av+0x168/0x2a0 [rdma_rxe]
</TASK>