Message-ID: <1339424543.7350.101.camel@marge.simpson.net>
Subject: Re: rcu: endless stalls
From: Mike Galbraith <mgalbraith@novell.com>
To: paulmck@linux.vnet.ibm.com
Cc: LKML <linux-kernel@vger.kernel.org>
Date: Mon, 11 Jun 2012 16:22:23 +0200
In-Reply-To: <20120611133953.GI2425@linux.vnet.ibm.com>
References: <1339409176.7350.26.camel@marge.simpson.net>
	 <20120611133953.GI2425@linux.vnet.ibm.com>
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On Mon, 2012-06-11 at 06:39 -0700, Paul E. McKenney wrote: 
> On Mon, Jun 11, 2012 at 12:06:16PM +0200, Mike Galbraith wrote:
> > Greetings,
> > 
> > I received a report of a 48 core UV box hitting a gripe, taking longer
> > than timeout to emit same, so box griped endlessly, forcing reboot.
> 
> So it took minutes to print an RCU CPU stall warning?  On only 48 CPUs?
> 
> If so, yow!!!

The report was a tad fuzzy on details, but serial console can take a
while at low baud rate, and the box was apparently perma-stalled.

> My guess is that rcu_cpu_stall_suppress must be manipulated atomically
> for this to work reliably, for example, using xchg().

Ah, thanks.

-Mike

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