From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
josh@joshtriplett.org, LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [RFC PATCH] rcu: don't ignore preempt_disable() in the idle loop
Date: Tue, 9 Mar 2010 18:28:00 -0800 [thread overview]
Message-ID: <20100310022800.GG6203@linux.vnet.ibm.com> (raw)
In-Reply-To: <4B970064.2040802@cn.fujitsu.com>
On Wed, Mar 10, 2010 at 10:13:56AM +0800, Lai Jiangshan wrote:
> Paul E. McKenney wrote:
> >>
> >> This is another try, it uses the fact that idle loops
> >> are executing with preept_count()=1.
> >> But I didn't look deep into all idle loops.
> >
> > Hello, Lai!
> >
> > One question below...
> >
> > Thanx, Paul
> >
>
> [...]
>
> >> +
> >> + if ((preempt_count() & PREEMPT_MASK) > IDLE_CORE_LOOP_PREEMPT_COUNT)
> >> + return 0;
> >
> > How does this work in CONFIG_PREEMPT=n kernels? I don't see how it
> > does, regardless of what preempt_count() returns in this case.
>
> You are right, It cannot work in CONFIG_PREEMPT=n kernels.
> ignore this stupid patch.
Don't be too hard on yourself -- it is an interesting idea, just doesn't
seem to quite work out. Perhaps it will lead you to another idea that
does work.
Thanx, Paul
prev parent reply other threads:[~2010-03-10 2:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-09 11:13 [RFC PATCH] rcu: don't ignore preempt_disable() in the idle loop Lai Jiangshan
2010-03-09 12:52 ` Steven Rostedt
2010-03-10 0:57 ` Lai Jiangshan
2010-03-10 13:51 ` Steven Rostedt
2010-03-10 0:54 ` Frederic Weisbecker
2010-03-10 1:30 ` Paul E. McKenney
2010-03-10 2:13 ` Lai Jiangshan
2010-03-10 2:28 ` Paul E. McKenney [this message]
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