Broadcom bge(4) panics while shutting down

Alexander Sack pisymbol at
Thu May 14 19:27:55 UTC 2009


Under heavy traffic (100% utilization GIGE on a 2 port BGE card)
running BGE CURRENT driver I see panics on shutdown.  The reason is
because bge_rxeof() while processing its RX ring of BD's drops the
softc lock when it hands it off to its input function.  If bge_stop()
is waiting for it, it will then proceed to acquire lock and then
quiesce the hardware (reseting the card, clearing out BDs etc.).  Once
bge_stop() releases the softc lock, then bge_rxeof() under an
interrupt context (no polling here) will reacquire and continue to
process the ring which is a bad idea.  It should check to see if the
card is still running before continuing processing BDs (i.e. once
IF_DRV_RUNNING has been reset by bge_stop(), bge_rxeof() is done, bail

Here is my first go around with this patch:

-- if_bge.c.CURRENT	2009-05-14 14:39:39.000000000 -0400
+++ if_bge.c	2009-05-14 14:39:24.000000000 -0400
@@ -3081,6 +3081,10 @@
 		uint16_t		vlan_tag = 0;
 		int			have_tag = 0;

+		if (!(ifp->if_drv_flags & IFF_DRV_RUNNING)) {
+			return;
+		}
 		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)

This prevents any panics during shutdown under heavy load and AS IT
TURNS out (I feel stupid for not looking) that em(4) already had this
check in its em_rxeof() function (right at the top of the loop).  I'm
more than happy changing it to the em style but above seems reasonable
to me though I have to verify there isn't anything missing off the
loop from a hardware standpoint (I don't think so because bge_stop()
did all the dirty work so I believe touching any registers after that
from bge_rxeof() is a bad idea).

Preliminary testing shows no more panics start and stopping ports
under heavy load (panics were almost immediate otherwise).



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