linux-kernel - Re: [PATCH 1/2] irq_flags_t: intro and core annotations

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Message-ID: <471EA9D6.9000004@garzik.org>
Date:	Tue, 23 Oct 2007 22:11:34 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	matthew@....cx, arnd@...db.de, ralf@...ux-mips.org,
	adobriyan@...il.com, viro@....linux.org.uk,
	viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/2] irq_flags_t: intro and core annotations

Herbert Xu wrote:
> Jeff Garzik <jeff@...zik.org> wrote:
>> Let me add to the chorus of voices:  I continually see two cases where 
>> real bugs crop up:
>>
>> 1) hacker uses spin_lock_irq() in incorrect context (where it is not 
>> safe to do a blind enable/disable)
>>
>> 2) hacker uses spin_lock_irq() correctly, but the surrounding code 
>> changes, thus invalidating prior assumptions.
>>
>> I would even go so far as to support the drastic measure of deleting 
>> spin_lock_irq().
>>
>> spin_lock_irqsave() generates fewer bugs, is more future-proof, and by 
>> virtue of 'flags' permits architectures a bit more flexibility.
> 
> Could we add a debug option that warned if spin_lock_irq is
> executed with IRQs turned off already?

Seems reasonable but perhaps arch-specific?

Also, I think someone (akpm?) mentioned an effort had been made before, 
and run into some problems.  I don't have details...

	Jeff



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