linux-kernel - Re: start_kernel(): bug: interrupts were enabled early

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Message-ID: <4BB3CE6A.2080406@zytor.com>
Date:	Wed, 31 Mar 2010 15:36:26 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rabin Vincent <rabin@....in>,
	lkml <linux-kernel@...r.kernel.org>, penberg@...helsinki.fi,
	cl@...ux-foundation.org, linux-arch@...r.kernel.org
Subject: Re: start_kernel(): bug: interrupts were enabled early

On 03/31/2010 03:31 PM, Benjamin Herrenschmidt wrote:
> On Wed, 2010-03-31 at 13:47 -0700, Yinghai Lu wrote:
>>> perhaps the second one isn't needed?  Perhaps no architecture
>> requires
>>> that local interrupts be disabled across the above initialisations?
>>         
>> spin_unlock_irq from arm is different from other archs?
> 
> No, it's not, it will enable IRQs and thats illegal to do so early
> during boot. We've been over that one again and again, the problem is
> that people want to keep using that instead of irqsave/restore because
> it's a nano-optimisation on x86... oh well...
> 

Well, guess what... the particular user in this case *isn't used at all
on x86* so it is a non-issue here.  So I take it we have your particular
vote to use irqsave/irqrestore in lib/rwsem-spinlock.c?

	-hpa
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