linux-kernel - Re: [PATCH v2] hardlockup: detect hard lockups without NMIs using secondary cpus

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Message-ID: <CAFTL4hxnCn13PigcWjrcnSV9RAz5gSX-VtQk9J8HEbQco7jbbQ@mail.gmail.com>
Date:	Tue, 15 Jan 2013 01:25:40 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Colin Cross <ccross@...roid.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Don Zickus <dzickus@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	liu chuansheng <chuansheng.liu@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v2] hardlockup: detect hard lockups without NMIs using
 secondary cpus

2013/1/15 Colin Cross <ccross@...roid.com>:
> On Mon, Jan 14, 2013 at 4:13 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>> I believe this is pretty much what the RCU stall detector does
>> already: checks for other CPUs being responsive. The only difference
>> is on how it checks that. For RCU it's about checking for CPUs
>> reporting quiescent states when requested to do so. In your case it's
>> about ensuring the hrtimer interrupt is well handled.
>>
>> One thing you can do is to enqueue an RCU callback (cal_rcu()) every
>> minute so you can force other CPUs to report quiescent states
>> periodically and thus check for lockups.
>
> That's a good point, I'll take a look at using that.  A minute is too
> long, some SoCs have maximum HW watchdog periods of under 30 seconds,
> but a call_rcu every 10-20 seconds might be sufficient.

Sure. And you can tune CONFIG_RCU_CPU_STALL_TIMEOUT accordingly.
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