linux-kernel - Re: lockdep and threaded IRQs (was: ...)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 2 Mar 2009 18:37:08 -0800
From:	David Brownell <david-b@...bell.net>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>, me@...ipebalbi.com,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	felipe.balbi@...ia.com, dmitry.torokhov@...il.com,
	sameo@...nedhand.com, tglx@...utronix.de
Subject: Re: lockdep and threaded IRQs (was: ...)

On Monday 02 March 2009, Ingo Molnar wrote:
> > 
> > p.s. Note that those changes would still leave the
> >      lockdep bug around ... it will still be breaking
> >      various drivers that use normal IRQs, by forcibly
> >      enabling IRQF_DISABLED.
> 
> it's not a bug - and i think Peter explained that already. 

No.  But I did get a non-response that didn't include any
explanation, and relied totally on unfounded assertions
combined with the presumption that someday IRQF_DISABLED
will be forced on in all drivers.

> It's  
> not really breaking things either - we've had this for more than 
> 2 years.

I happened across two MMC host adapter drivers which it
broke.  They preceded the patch whereby lockdep changes
request_irq() semantics.  The drivers break only with
lockdep ... so platforms relying on those can't use lockdep.
No reason to think there aren't more such bugs lurking.

We also wasted quite a few months tracking down USB bugs
that were masked by that patch ... the indeterminacy of
IRQF_DISABLED behavior given IRQF_SHARED was hidden by
enabling lockdep.  Led to a lot of totally crapulous oops
traces, I assure you.

So ... it has most certainly broken things.  There has
seemed to be a bit of stick-fingers-in-ears going on, that
prevents hearing about such problems though.

- Dave

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/