Date: Thu, 14 May 2009 12:47:16 -0700 From: Xin LI <delphij@delphij.net> To: Alexander Sack <pisymbol@gmail.com> Cc: freebsd-current@freebsd.org Subject: Re: Broadcom bge(4) panics while shutting down Message-ID: <4A0C7544.6010304@delphij.net> In-Reply-To: <3c0b01820905141202w113966dp4bfbab73d84d585@mail.gmail.com> References: <3c0b01820905141202w113966dp4bfbab73d84d585@mail.gmail.com>
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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
> @@ -3081,6 +3081,10 @@
> 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@delphij.net> http://www.delphij.net/
FreeBSD - The Power to Serve!
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