linux-kernel - Re: v2.6.21-rt2

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Message-ID: <20070516220444.GA27081@elte.hu>
Date:	Thu, 17 May 2007 00:04:44 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: v2.6.21-rt2

* Daniel Walker <dwalker@...sta.com> wrote:

> I don't know. irqs_off_preempt_count() could get used someplace else, 
> where you would want to flip the preempt_count() check .. It seems 
> sane to combine your patch with mine ..
> 
> irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && 
> preempt_count())
> 
> You can't call __get_cpu_var() without the a positive preempt_count(), 
> so the check seems backwards regardless of the other factors ..

yeah. The whole trace_preempt_enter_idle() thing looks a bit suspect. 
Why cannot those architectures simply disable/enable preemption and get 
the same effect? It's not like we ever want to allow the preemption of 
the idle task.

and once that is solved, irqs_off_preempt_count() can again include the 
hardirq and preempt count check only and doesnt have to check the 
idle_cpu flag. This would make the whole thing simpler and would avoid 
silly bugs like this.

	Ingo
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