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Date: Wed, 1 Jun 2005 21:39:06 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>, Karim Yaghmour <karim@opersys.com>,
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       Sven-Thorsten Dietrich <sdietrich@mvista.com>, dwalker@mvista.com,
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Subject: Re: RT patch acceptance
Message-ID: <20050601193906.GA26939@elte.hu>
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* Andrea Arcangeli <andrea@suse.de> wrote:

> > So if PREEMPT-RT would use a soft cli/sti emulation, no problem should
> > arise.
> 
> So I wonder why it doesn't do that and it leaves local_irq_disable
> uncovered [...]
>
> Perhaps that's planned and not yet implemented?

yes. As i said in an earlier mail:

> > (there are still some ways to introduce latencies into PREEMPT_RT, 
> > but they are not common and we are working on ways to cover them
> > all.)
 
local_irq_disable() is one way, preempt_disable() is another way. Adding 
asm("cli") to your driver is a third way. In practice these items are 
not a big issue, so i'm not yet covering them. It's a small detail.  
Check the amount of local-irq-disable instances in the driver space vs.  
spinlock use.

	Ingo