linux-kernel - Re: floppy driver assumes INITIAL

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Message-ID: <alpine.LFD.2.00.1006031606040.8175@i5.linux-foundation.org>
Date:	Thu, 3 Jun 2010 16:09:12 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Stephen Hemminger <shemminger@...tta.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: floppy driver assumes INITIAL_JIFFIES == 0

On Thu, 3 Jun 2010, Stephen Hemminger wrote:
> 
> Thank you for confirming my suspicions.  Given the state of destruction
> there, bug fixing is like playing Jenga.

I suspect it's fixable, but it would probably involve a lot of careful 
moving around of that "floppy_lock" spinlock. Add various asserts to make 
sure that it's held in all cases, and then for each warning you get, you 
add the proper spinlock until it's all properly protected.

The _original_ protection was just from irqs being atomic (UP, remember), 
and the block layer queueing happening from irq-safe context. You're still 
running it on UP, but we've even lost the irq-handler protection (and then 
later, the bottom-half mutual exclusion).

			Linus
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