linux-kernel - Re: [RFC][PATCH] rcu: Hotplug and PROVE_RCU

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Message-ID: <20130604131408.GK11597@linux.vnet.ibm.com>
Date:	Tue, 4 Jun 2013 06:14:08 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] rcu: Hotplug and PROVE_RCU_DELAY not playing well
 together

On Mon, Jun 03, 2013 at 02:19:51PM -0400, Steven Rostedt wrote:
> On Sun, 2013-06-02 at 07:18 -0700, Paul E. McKenney wrote:
> 
> > ------------------------------------------------------------------------
> > 
> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> > index d12470e..9a08bdc 100644
> > --- a/kernel/rcutree.c
> > +++ b/kernel/rcutree.c
> > @@ -1320,9 +1320,9 @@ static int rcu_gp_init(struct rcu_state *rsp)
> >  					    rnp->grphi, rnp->qsmask);
> >  		raw_spin_unlock_irq(&rnp->lock);
> >  #ifdef CONFIG_PROVE_RCU_DELAY
> > -		if ((prandom_u32() % (rcu_num_nodes * 8)) == 0 &&
> > +		if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 &&
> >  		    system_state == SYSTEM_RUNNING)
> > -			schedule_timeout_uninterruptible(2);
> > +			udelay(200);
> >  #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
> >  		cond_resched();
> >  	}
> 
> I ran this for a bit. Where it usually crashes in less than a minute,
> this ran for over 10 minutes without issue.
> 
> Tested-by: Steven Rostedt <rostedt@...dmis.org>

Thank you!!!

And yes, if this was production code rather than test code, I probably
would have favored a solution like yours.

							Thanx, Paul

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