linux-kernel - Re: [PATCH v3] printk: Avoid softlockups in console

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Message-ID: <20130301215346.GF3285@linux.vnet.ibm.com>
Date:	Fri, 1 Mar 2013 13:53:46 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jan Kara <jack@...e.cz>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] printk: Avoid softlockups in console_unlock()

On Fri, Mar 01, 2013 at 01:43:21PM -0800, Andrew Morton wrote:
> On Fri, 1 Mar 2013 11:30:27 +0100
> Jan Kara <jack@...e.cz> wrote:
> 
> > > If a CPU remains in your loop where you invoke rcu_cpu_stall_reset(),
> > > there is no indication of the stall.  Now, I do understand why having
> > > RCU add a CPU stall warning into the mix would be very bad, but it
> > > would be good to have some sort of indication that there is stalling.
> > > Perhaps a counter visible in sysfs?  Whatever it is, at least some way
> > > of diagnosing the stall condition would be very good.
> >   I see. If others (Andrew, ping?) are OK with the rest of the patch, I can
> > extend it and add a counter of printk() breaks we had to make. That looks
> > like a good idea.
> 
> hmpf, spose so.  It sound lke the world's least interesting counter but
> perhaps it will look more interesting when we see its sparkly
> documentation.

Boredom is a good thing here, given that the goal is to reduce
excitement when bad things happen.  Or at least to increase awareness
of root causes.

							Thanx, Paul

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