Date: Mon, 29 Jun 2015 13:55:28 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>, laijs@cn.fujitsu.com,
        dipankar@in.ibm.com, Andrew Morton <akpm@linux-foundation.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        David Howells <dhowells@redhat.com>,
        Eric Dumazet <edumazet@google.com>,
        Darren Hart <dvhart@linux.intel.com>,
        =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, pranith kumar <bobby.prani@gmail.com>
Subject: Re: [PATCH tip/core/rcu 24/24] rcu: Conditionally compile RCU's eqs
 warnings
Message-ID: <20150629205528.GQ3717@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <20150512223034.GA1396@linux.vnet.ibm.com>
 <1431469854-3826-1-git-send-email-paulmck@linux.vnet.ibm.com>
 <1431469854-3826-24-git-send-email-paulmck@linux.vnet.ibm.com>
 <CAMuHMdVjuZhhMhcpupZteXMvfLKK=nyw8--HCW-c+PKT-k8kxA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAMuHMdVjuZhhMhcpupZteXMvfLKK=nyw8--HCW-c+PKT-k8kxA@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1861
Lines: 51

On Mon, Jun 29, 2015 at 11:39:13AM +0200, Geert Uytterhoeven wrote:
> Hi Paul,
> 
> On Wed, May 13, 2015 at 12:30 AM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -1373,6 +1373,17 @@ config RCU_TRACE
> >           Say Y here if you want to enable RCU tracing
> >           Say N if you are unsure.
> >
> > +config RCU_EQS_DEBUG
> > +       bool "Use this when adding any sort of NO_HZ support to your arch"
> 
> This sounds a bit fuzzy. Can you please provide a better one-line description?
> Thanks!

So the point of this Kconfig option is to provide WARN_ON()s that catch
bug such as telling RCU that a given CPU entered idle, but failing to
tell RCU when that CPU later leaves idle.  So how about this?

+       bool "Provide debugging asserts for adding NO_HZ support to an arch"

							Thanx, Paul

> > +       depends on DEBUG_KERNEL
> > +       help
> > +         This option provides consistency checks in RCU's handling of
> > +         NO_HZ.  These checks have proven quite helpful in detecting
> > +         bugs in arch-specific NO_HZ code.
> > +
> > +         Say N here if you need ultimate kernel/user switch latencies
> > +         Say Y if you are unsure
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/