netdev - Re: 2.6.24 BUG: soft lockup

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Date:	Fri, 28 Mar 2008 11:56:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Herbert Xu <herbert@...dor.apana.org.au>
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


* Herbert Xu <herbert@...dor.apana.org.au> wrote:

> > This runs from softirqs, the local thread's scheduling state is 
> > updated from timers which also run from softirqs, so this 
> > need_resched() test won't work.
> 
> I had a trawl through the scheduler/timer code and it appears that 
> even with softirqs disabled we should able to set the flag through 
> this call chain (on x86-32):
> 
> timer_interrupt => do_timer_interrupt_hook => tick_handle_periodic => 
> tick_periodic => update_process_times => scheduler_tick
> 
> Ingo, could you confirm that the scheduler is capable of setting 
> need_resched even with BH disabled?

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.

	Ingo
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