linux-kernel - Re: [RFC][PATCH] IRQ: Fix oneshot irq race between irq_finalize_oneshot and handle_level

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Message-ID: <20100311091339.GD8389@windriver.com>
Date:	Thu, 11 Mar 2010 17:13:39 +0800
From:	Yong Zhang <yong.zhang@...driver.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Lars-Peter Clausen <lars@...afoo.de>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] IRQ: Fix oneshot irq race between
 irq_finalize_oneshot and handle_level_irq

On Thu, Mar 11, 2010 at 09:41:45AM +0100, Thomas Gleixner wrote:
> No, it is _NOT_ harmless. interrupt handlers are guaranteed _NOT_ to
> be reentered. That's why we check the INPROGRESS flag. 
> 
> And you totally miss the case which caused the disussion in the first
> place: When the thread finishes _before_ the hard irq handler on the
> other CPU has set IRQ_MASKED. So this patch solves nothing at all, it
> just makes stuff worse than it was.
> 
> Here is the solution which solves the inconsistent lock state _AND_
> the reentrancy race.
> 
> http://git.kernel.org/?p=linux/kernel/git/tip/linux-2.6-tip.git;a=commit;h=0b1adaa031a55e44f5dd942f234bf09d28e8a0d6
> 
> The change log has a full explanation of the scenarios.

Yeah, I see. Thanks for your point.
It will smooth the concerns.

Thanks,
Yong
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