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Date: Wed, 10 Mar 2010 10:13:56 +0800
From: Lai Jiangshan <laijs@cn.fujitsu.com>
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To: paulmck@linux.vnet.ibm.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
References: <4B962D57.1000406@cn.fujitsu.com> <20100310013035.GB6203@linux.vnet.ibm.com>
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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.

Thanx, Lai