linux-kernel - Re: [Bugme-new] [Bug 10326] New: inconsistent lock state in net_rx

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Date:	Thu, 27 Mar 2008 04:03:34 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	a.p.zijlstra@...llo.nl
Cc:	akpm@...ux-foundation.org, jarkao2@...il.com,
	netdev@...r.kernel.org, bugme-daemon@...zilla.kernel.org,
	marcus@...ter.se, shemminger@...ux-foundation.org, rjw@...k.pl,
	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [Bugme-new] [Bug 10326] New: inconsistent lock state in
 net_rx_action

From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Thu, 27 Mar 2008 11:56:19 +0100

> How about this:
> 
> <irqs disabled>
> 
>   netpoll_poll()
>     poll_napi()
>       spin_trylock(&napi->poll_lock)
>       poll_one_napi()
>         napi->poll() := sky2_poll()
>           napi_complete()
>             local_irq_disable()
>             local_irq_enable() <--- *BUG*
> 
>   <irq>
>     irq_exit()
>       do_softirq()
>         net_rx_action()
>           spin_lock(&napi->poll_lock) <--- Deadlock!
> 
> Because we still hold the lock....

Yep, that will deadlock.

Can some test if using local_irq_{save,restore}() in
napi_complete() cures this lockdep warning?

Thanks.
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