netdev - Re: 2.6.24 BUG: soft lockup

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Message-ID: <20080328110621.GA23342@gondor.apana.org.au>
Date:	Fri, 28 Mar 2008 19:06:21 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	David Miller <davem@...emloft.net>, Matheos.Worku@....COM,
	jesse.brandeburg@...el.com, jarkao2@...il.com,
	netdev@...r.kernel.org, hadi@...erus.ca
Subject: Re: 2.6.24 BUG: soft lockup - CPU#X

On Fri, Mar 28, 2008 at 11:56:29AM +0100, Ingo Molnar wrote:
>
> hm, what's the context of this discussion? The call chain looks ok, 
> that's how we preempt tasks from the timer tick. But other code besides 
> the scheduler shouldnt do this.

The code under discussion is __qdisc_run from net/sched/sch_generic.c.

It runs with BH off from either process context or softirq context.
As it is it can keep running forever.  We were discussing adding
a need_resched check in there.  So the question is would need_resched
ever get updated while BH is disabled?

Anyway, I've just realised that even if it does get updated, we still
need a better bound to avoid starving other local softirq events so
this is probably moot.

Thanks,
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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