linux-kernel - Re: [PATCH] hardlockup: detect hard lockups without NMIs using secondary cpus

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]

Date:	Thu, 10 Jan 2013 17:18:40 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Don Zickus <dzickus@...hat.com>, Colin Cross <ccross@...roid.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	liu chuansheng <chuansheng.liu@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] hardlockup: detect hard lockups without NMIs using
 secondary cpus

2013/1/10 Russell King - ARM Linux <linux@....linux.org.uk>:
> On Thu, Jan 10, 2013 at 09:02:15AM -0500, Don Zickus wrote:
>> On Wed, Jan 09, 2013 at 05:57:39PM -0800, Colin Cross wrote:
>> > Emulate NMIs on systems where they are not available by using timer
>> > interrupts on other cpus.  Each cpu will use its softlockup hrtimer
>> > to check that the next cpu is processing hrtimer interrupts by
>> > verifying that a counter is increasing.
>> >
>> > This patch is useful on systems where the hardlockup detector is not
>> > available due to a lack of NMIs, for example most ARM SoCs.
>>
>> I have seen other cpus, like Sparc I think, create a 'virtual NMI' by
>> reserving an IRQ line as 'special' (can not be masked).  Not sure if that
>> is something worth looking at here (or even possible).
>
> No it isn't, because that assumes that things like spin_lock_irqsave()
> won't mask that interrupt.  We don't have the facility to do that.

I believe sparc is doing something like this though. Look at
arch/sparc/include/asm/irqflags_64.h, it seems NMIs are implemented
there using an irq number that is not masked by this function.

Not all archs can do that so easily I guess.
--
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/