linux-kernel - Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <alpine.LFD.2.00.1003251211350.3147@localhost.localdomain>
Date:	Thu, 25 Mar 2010 12:16:17 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>, jesse.brandeburg@...el.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] Prevent nested interrupts when the IRQ stack is near
 overflowing v2

On Thu, 25 Mar 2010, Alan Cox wrote:

> > Which leads to the general question why we have that IRQF_DISABLED
> > shite at all. AFAICT the historical reason were IDE drivers, but we
> > grew other abusers like USB, SCSI and other crap which runs hard irq
> > handlers for hundreds of micro seconds in the worst case.
> 
> Anyone you've forgotten to offend ?

Hmm, not sure. Have not measured IRQ handler run times for quite a
while :)

> Pretty much the only 'core' driver today which enables IRQs in the irq
> handlers and needs it is the old IDE layer. There are also a couple of
> drivers which play games with disable/enable_irq in the IRQ paths for
> other reasons (lack of irq threads when written and a hardware model thats
> totally SMP unfriendly). 8390 is the obvious one here and it at least
> would be far far saner using threaded IRQs and normal locking with IRQs
> unmasked.

Right, but that's not the problem here. We talk about a (hopefully)
well written interrupt handler which runs for a very short
time. What's the point of running it with interrupts enabled ?
Nothing, we just run into stack overflow problems. So what's better:
an unreliable and ugly hackaround or just avoiding the possible stack
overflow in the first place ?

Thanks,

	tglx


--
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/