linux-kernel - Re: [PATCH 07/33] nohz: Basic full dynticks interface

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Message-ID: <20130220163258.GB16780@pd.tnic>
Date:	Wed, 20 Feb 2013 17:32:58 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 07/33] nohz: Basic full dynticks interface

On Mon, Feb 11, 2013 at 03:35:29PM +0100, Borislav Petkov wrote:
> > +/* Parse the boot-time nohz CPU list from the kernel parameters. */
> > +static int __init tick_nohz_full_setup(char *str)
> > +{
> > +	alloc_bootmem_cpumask_var(&full_nohz_mask);
> > +	have_full_nohz_mask = true;
> > +	cpulist_parse(str, full_nohz_mask);
> 
> Don't you want to check retval of cpulist_parse first here before
> assigning have_full_nohz_mask and allocating cpumask var?
> 
> We don't trust userspace, you know.
> 
> > +	return 1;
> > +}
> > +__setup("full_nohz=", tick_nohz_full_setup);

One more thing. AFAICT, full_nohz requires rcu_nocbs to pass in the same
mask, right?

Maybe tick_nohz_full_setup() could be made to call rcu_nocb_setup()
without the need to pass "rcu_nocbs=" option on the cmd line; in the
sense that if user supplies a full_nohz mask, she wants the same mask
for rcu_nocbs...

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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