On 20/10/2022 15:37, 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> > > > Best wishes, > Jia-Ju Bai Hi I don't know whether this deadlock is real or not, but I wrote the offending code. If it's a real bug, I'm sorry about that. If that's the case the bug is also present in 2 other places of rvt_ruc_loopback() in v5.19+: 1) spin_lock_irqsave(&sqp->s_lock, flags); --> Line 3133 spin_lock(&sqp->r_lock); --> Line 3137 2) spin_lock_irqsave(&sqp->s_lock, flags); --> Line 3192 spin_lock(&sqp->r_lock); --> Line 3193 Kind regards Niels
