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

[Dennis Dalessandro]

On 10/20/22 9:37 AM, Jia-Ju Bai wrote:
> 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>

Thanks, we'll look into them.

-Denny