Re: Broadcom bge(4) panics while shutting down

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Hi, Alexander,

Alexander Sack wrote:
> Hello:
> 
> 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
> out).
> 
> 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
> _at__at_ -3081,6 +3081,10 _at__at_
>  		uint16_t		vlan_tag = 0;
>  		int			have_tag = 0;
> 
> +		if (!(ifp->if_drv_flags & IFF_DRV_RUNNING)) {
> +			return;
> +		}
> +
>  #ifdef DEVICE_POLLING
>  		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).
> 
> 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?

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