linux-kernel - Re: [PATCH -rt DO NOT APPLY] Fix for tg3 networking lockup

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Message-ID: <Pine.LNX.4.58.0608070124340.15870@gandalf.stny.rr.com>
Date:	Mon, 7 Aug 2006 01:34:56 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Theodore Tso <tytso@....edu>
cc:	David Miller <davem@...emloft.net>, mchan@...adcom.com,
	herbert@...dor.apana.org.au, LKML <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH -rt DO NOT APPLY] Fix for tg3 networking lockup

On Thu, 3 Aug 2006, Theodore Tso wrote:

> On Thu, Aug 03, 2006 at 02:48:45PM -0700, David Miller wrote:
> > > eth0: Tigon3 [partno(BCM95704s) rev 2100 PHY(serdes)] (PCIX:100MHz:64-bit) 10/100/1000BaseT Ethernet 00:14:5e:86:44:24
> >
> > The 5704 chip will set TG3_FLAG_TAGGED_STATUS, and therefore
> > doesn't need the periodic poking done by tg3_timer().
>
> Hmm.... all I can say is that I could reliably knock the box off the
> network by running a four processes that tied up all CPU's at high
> real-time priorities, and after I applied the horrible hack that
> guaranteed that tg3_timer() was run every 0.128 seconds, the system
> stayed on the network.  I'm not sure why, but it did fix the problem.
>
> Any suggestions on how I could figure out what was really going on and
> what would be a better fix would be greatly appreciated.
>

Ted,

I took a quick look at the tg3 driver and that timer interrupt as well
have read this thread.  My suggestion would be to separate that tg3_timer
into 4 different timers, which is what it actually looks like.  One I
believe (the first one) is an actual timeout and the other three are
timers that are expected to be triggered everytime (watchdog like: at 1
second, 2 seconds and 3 seconds) and thus should be converted into a
hrtimers that goes off when expected then having some crazy accounting
thing in one timer.

I don't fully understand the ASF part here, and if it definitely needs to
go off then set that timer  with the highest prio.  I've ask Thomas to
add a way to add a hrtimer with a given prio instead of always taking the
current->normal_prio.  But until he does that, you can do a hack of
changing the current prio to something very high (like 99) then start the
timer, and then lower the prio back to what it was.  This is a hack, but
it might lead to a better solution in the future.

-- Steve

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