Date: Thu, 2 Feb 2012 10:00:48 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com,
        dipankar@in.ibm.com, akpm@linux-foundation.org,
        mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de,
        peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
        dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
        fweisbec@gmail.com, patches@linaro.org,
        "Paul E. McKenney" <paul.mckenney@linaro.org>,
        Julia Lawall <julia@diku.dk>
Subject: Re: [PATCH RFC tip/core/rcu 31/41] rcu: Add CPU-stall capability to
 rcutorture
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On Wed, Feb 01, 2012 at 09:53:11PM -0800, Josh Triplett wrote:
> On Wed, Feb 01, 2012 at 11:41:49AM -0800, Paul E. McKenney wrote:
> > --- a/kernel/rcutorture.c
> > +++ b/kernel/rcutorture.c
> > +/* Spawn CPU-stall kthread, if stall_cpu specified. */
> > +static int __init rcu_torture_stall_init(void)
> > +{
> > +	if (stall_cpu <= 0)
> > +		return 0;
> > +	stall_task = kthread_run(rcu_torture_stall, NULL, "rcu_torture_stall");
> > +	if (IS_ERR(stall_task)) {
> > +		stall_task = NULL;
> > +		return PTR_ERR(stall_task);
> 
> This seems...unlikely to produce the desired result. :)

Error?  What error?

Good eyes, fixed!

> A quick check turns up the same bug in rcutorture_onoff_init.

Which is of course where I started when creating rcu_torture_stall_init().

> This suggests a possible Coccinelle check, for uses of PTR_ERR(foo) after
> foo = (any constant other than ERR_PTR(foo)).

And I took the resulting patch, thank you!

							Thanx, Paul

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