From: Peter Zijlstra <peterz@infradead.org>
To: paulmck@linux.vnet.ibm.com
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Ingo Molnar <mingo@elte.hu>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] rcutorture: add random preemption
Date: Mon, 21 Jun 2010 18:50:11 +0200 [thread overview]
Message-ID: <1277139011.1875.522.camel@laptop> (raw)
In-Reply-To: <20100621164306.GC2354@linux.vnet.ibm.com>
On Mon, 2010-06-21 at 09:43 -0700, Paul E. McKenney wrote:
> > +#ifdef CONFIG_PREEMPT
> > + if (!preempt_count() && !(rcu_random(rrsp) % (nrealreaders * 20000)))
> > + preempt_schedule();
> > +#endif
>
> This one scared me for a bit -- then I realized that preempt_schedule()
> won't actually schedule if preemption is in any way disabled. So the
> above really is OK, because Classic RCU and RCU-bh disable preemption.
>
> So, should we have a comment to this effect, or is my hypersensitivity to
> RCU semantics unique to me?
Well it seems to do a !preempt_count() test too, so I wouldn't worry too
much about it, still using preempt_schedule() doesn't seem right, why
not use cond_resched()?
next prev parent reply other threads:[~2010-06-21 16:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-21 8:57 [PATCH] rcutorture: add random preemption Lai Jiangshan
2010-06-21 16:43 ` Paul E. McKenney
2010-06-21 16:50 ` Peter Zijlstra [this message]
2010-06-21 17:05 ` Paul E. McKenney
2010-06-21 17:06 ` Peter Zijlstra
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