[BUG] infiniband: sw: rdmavt: possible ABBA deadlocks in rvt_ruc_loopback()

[Jia-Ju Bai]

Hello,

My static analysis tool reports several possible ABBA deadlock in the 
rdmavt driver in Linux 5.18:

rvt_ruc_loopback()
  spin_lock_irqsave(&sqp->s_lock, flags); --> Line 3190 (Lock A)
  spin_lock(&sqp->r_lock); --> Line 3195 (Lock B)

rvt_qp_mr_clean()
  spin_lock_irq(&qp->r_lock); --> Line 698 (Lock B)
  spin_lock(&qp->s_lock); --> Line 700 (Lock A)

rvt_rc_timeout()
  spin_lock_irqsave(&qp->r_lock, flags); --> Line 2595 (Lock B)
  spin_lock(&qp->s_lock); --> Line 2596 (Lock A)

rvt_modify_qp()
  spin_lock_irq(&qp->r_lock); --> Line 1419 (Lock B)
  spin_lock(&qp->s_lock); --> Line 1421(Lock A)

_rvt_reset_qp()
  spin_lock_irq(&qp->r_lock); --> Line 907 (Lock B)
  spin_lock(&qp->s_lock); --> Line 909 (Lock A)

rvt_reset_qp()
  spin_lock_irq(&qp->r_lock); --> Line 936 (Lock B)
  spin_lock(&qp->s_lock); --> Line 938 (Lock A)

When rvt_ruc_loopback() is concurrently executed with rvt_qp_mr_clean(), 
rvt_rc_timeout(), rvt_modify_qp(), _rvt_reset_qp() or rvt_reset_qp(), 
the deadlocks can occur.

I am not quite sure whether these possible deadlocks are real and how to 
fix them if real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>


Best wishes,
Jia-Ju Bai