[BUG] infiniband: hw: hfi1: possible ABBA deadlock in pio_wait() and sc_disable()

[Jia-Ju Bai]

Hello,

My static analysis tool reports a possible ABBA deadlock in the hfi1 
driver in Linux 5.10:

sc_disable()
  write_seqlock(&sc->waitlock); --> Line 956 (Lock A)
  hfi1_qp_wakeup()
    spin_lock_irqsave(&qp->s_lock, flags); --> Line 441 (Lock B)

pio_wait()
  spin_lock_irqsave(&qp->s_lock, flags); --> Line 939 (Lock B)
  write_seqlock(&sc->waitlock); --> Line 941 (Lock A)

When sc_disable() and pio_wait() are concurrently executed, the deadlock 
can occur.

I am not quite sure whether this possible deadlock is real and how to 
fix it if it is real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>


Best wishes,
Jia-Ju Bai