netdev - Re: 2.6.24 BUG: soft lockup

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Message-ID: <20080328102931.GA23039@gondor.apana.org.au>
Date:	Fri, 28 Mar 2008 18:29:31 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	Matheos.Worku@....COM, jesse.brandeburg@...el.com,
	jarkao2@...il.com, netdev@...r.kernel.org, hadi@...erus.ca,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: 2.6.24 BUG: soft lockup - CPU#X

On Thu, Mar 27, 2008 at 06:38:44PM -0700, David Miller 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?

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