Re: Broadcom bge(4) panics while shutting down

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Hi, Alexander,

Alexander Sack wrote:
[...]
>>> Preliminary testing shows no more panics start and stopping ports
>>> under heavy load (panics were almost immediate otherwise).
>>>
>>> Thoughts?
>> I think this would solve the problem but I'm not sure whether this would
>> increase some overhead on the RX path.  It seems that there is a race
>> between bge_release_resources() and bge_intr(), I mean, it might be a
>> good idea to "drain" bge_intr() instead?
> 
> Are you talking about detach time?  Because bge_stop() gets called
> before bge_release_resources() and stops host interrupts so where is
> the race again?  I mean at this point no more interrupts should be
> delivered to bge_intr() (I can confirm from spec since BGE has
> released it in the wild).  So why would you "drain" it at this
> point....(the hardware is down including the firmware).
> 
> I agree it adds a little overhead to the standard bge_rxeof() path
> which I agree is very sensitive to change.  However, I think the check
> at top is tolerable since the other recourse is crash.  I mean its
> very easy to reproduce.  Flood a Broadcom card with traffic then stop
> the card and let the race begin...it will go down in bge_rxeof() after
> bge_stop releases the lock.
> 
> I actually did not look at changing anything structurally to perhaps
> make this whole predicament better but minimally there should be a
> shield against this no?

I'm all for a workaround at this point, but I really want to make sure
that we are doing things in a safer manner if we can reach it timely.

What about something like this, in my opinion, because bge_rxeof() would
unlock sc in the middle, it would be probably better to re-check the
IFF_DRV_RUNNING flag and avoid calling txeof after that (I've moved the
condition to after we re-grab the lock to match the rest of the code:

=====
[delphij_at_charlie] /sys/dev/bge> svn diff -x -p
Index: if_bge.c
===================================================================
- --- if_bge.c	(revision 191995)
+++ if_bge.c	(working copy)
_at__at_ -3073,7 +3073,7 _at__at_ bge_rxeof(struct bge_softc *sc)
 		bus_dmamap_sync(sc->bge_cdata.bge_rx_jumbo_ring_tag,
 		    sc->bge_cdata.bge_rx_jumbo_ring_map, BUS_DMASYNC_POSTREAD);

- -	while(sc->bge_rx_saved_considx !=
+	while (sc->bge_rx_saved_considx !=
 	    sc->bge_ldata.bge_status_block->bge_idx[0].bge_rx_prod_idx) {
 		struct bge_rx_bd	*cur_rx;
 		uint32_t		rxidx;
_at__at_ -3193,6 +3193,9 _at__at_ bge_rxeof(struct bge_softc *sc)
 		BGE_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);
 		BGE_LOCK(sc);
+
+		if (!(ifp->if_drv_flags & IFF_DRV_RUNNING))
+			return;
 	}

 	if (stdcnt > 0)
_at__at_ -3301,6 +3304,10 _at__at_ bge_poll(struct ifnet *ifp, enum poll_cmd cmd, int

 	sc->rxcycles = count;
 	bge_rxeof(sc);
+	if (!(ifp->if_drv_flags & IFF_DRV_RUNNING)) {
+		BGE_UNLOCK(sc);
+		return;
+	}
 	bge_txeof(sc);
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		bge_start_locked(ifp);
_at__at_ -3370,7 +3377,9 _at__at_ bge_intr(void *xsc)
 	if (ifp->if_drv_flags & IFF_DRV_RUNNING) {
 		/* Check RX return ring producer/consumer. */
 		bge_rxeof(sc);
+	}

+	if (ifp->if_drv_flags & IFF_DRV_RUNNING) {
 		/* Check TX ring producer/consumer. */
 		bge_txeof(sc);
 	}

Cheers,
- --
Xin LI <delphij_at_delphij.net>	http://www.delphij.net/
FreeBSD - The Power to Serve!
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