linux-kernel - Re: [PATCH RFC tip/core/rcu 31/41] rcu: Add CPU-stall capability to rcutorture

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Date:	Thu, 2 Feb 2012 10:00:48 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	Julia Lawall <julia@...u.dk>
Subject: Re: [PATCH RFC tip/core/rcu 31/41] rcu: Add CPU-stall capability to
 rcutorture

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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