On Wed, Mar 23, 2022 at 12:43:03PM +0100, Hans Schultz wrote: > On ons, mar 23, 2022 at 13:21, Vladimir Oltean <olteanv@xxxxxxxxx> wrote: > > On Wed, Mar 23, 2022 at 11:57:16AM +0100, Hans Schultz wrote: > >> >> >> Another issue I see, is that there is a deadlock or similar issue when > >> >> >> receiving violations and running 'bridge fdb show' (it seemed that > >> >> >> member violations also caused this, but not sure yet...), as the unit > >> >> >> freezes, not to return... > >> >> > > >> >> > Have you enabled lockdep, debug atomic sleep, detect hung tasks, things > >> >> > like that? > >> >> > >> >> I have now determined that it is the rtnl_lock() that causes the > >> >> "deadlock". The doit() in rtnetlink.c is under rtnl_lock() and is what > >> >> takes care of getting the fdb entries when running 'bridge fdb show'. In > >> >> principle there should be no problem with this, but I don't know if some > >> >> interrupt queue is getting jammed as they are blocked from rtnetlink.c? > >> > > >> > Sorry, I forgot to respond yesterday to this. > >> > By any chance do you maybe have an AB/BA lock inversion, where from the > >> > ATU interrupt handler you do mv88e6xxx_reg_lock() -> rtnl_lock(), while > >> > from the port_fdb_dump() handler you do rtnl_lock() -> mv88e6xxx_reg_lock()? > >> > >> If I release the mv88e6xxx_reg_lock() before calling the handler, I need > >> to get it again for the mv88e6xxx_g1_atu_loadpurge() call at least. But > >> maybe the vtu_walk also needs the mv88e6xxx_reg_lock()? > >> I could also just release the mv88e6xxx_reg_lock() before the > >> call_switchdev_notifiers() call and reacquire it immediately after? > > > > The cleanest way to go about this would be to have the call_switchdev_notifiers() > > portion of the ATU interrupt handling at the very end of mv88e6xxx_g1_atu_prob_irq_thread_fn(), > > with no hardware access needed, and therefore no reg_lock() held. > > So something like? > mv88e6xxx_reg_unlock(chip); > rtnl_lock(); > err = call_switchdev_notifiers(SWITCHDEV_FDB_ADD_TO_BRIDGE, brport, &info.info, NULL); > rtnl_unlock(); > mv88e6xxx_reg_lock(chip); No, call_switchdev_notifiers() should be the very end, no reg_lock() afterwards. Do all the hardware handling you need, populate some variables to denote that you need to notify switchdev, and if you do, lock the rtnetlink mutex and do it.
