linux-kernel - Re: Threaded irqs + 100% CPU RT task = RCU stall

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Message-ID: <alpine.LFD.2.02.1303061651360.22263@ionos>
Date:	Wed, 6 Mar 2013 16:58:54 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Threaded irqs + 100% CPU RT task = RCU stall

On Wed, 6 Mar 2013, Paul Gortmaker wrote:
> So, I guess the question is, whether we want to try and make the system
> fail in a more meaningful way -- kind of like the rt throttling message
> does - as it lets users know they've hit the wall?  Something watching

That Joe Doe should have noticed the throttler message, which came
before the stall, shouldn't he?

> for kstat_incr_softirqs traffic perhaps?  Or other options?

The rcu stall detector could use the softirq counter and if it did not
change in the stall period print: "Caused by softirq starvation" or
something like that.

Thanks,

	tglx


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