linux-kernel - Re: [PATCH] RFC: Set irq thread to RT priority on creation

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Message-ID: <alpine.LFD.2.02.1305301602490.2905@ionos>
Date:	Thu, 30 May 2013 16:07:43 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ivo Sieben <meltedpianoman@...il.com>
cc:	RT <linux-rt-users@...r.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RFC: Set irq thread to RT priority on creation

On Thu, 30 May 2013, Ivo Sieben wrote:

> When a threaded irq handler is installed the irq thread is initially created
> on normal scheduling priority. Only after the the irq thread is woken up it
> sets its priority to RT_FIFO MAX_USER_RT_PRIO/2.
> 
> This means that interrupts that occur directly after the irq handler is
> installed will be handled on a normal scheduling priority instead of the
> realtime priority that you would expect. Fixed this by setting the RT
> priority on creation of the irq_thread.
> 
> Signed-off-by: Ivo Sieben <meltedpianoman@...il.com>
> ---
> 
> RFC:
> Whas there a specific reason for the irq_thread to be created on normal
> scheduling and only set to RT priority when woken up?

No.

> This patch solves an issue for me where a device driver is expected to handle an
> interrupt immediatly after irq handlers are installed and interrupts enabled.

You miss to explain what kind of issue that is.

Thanks,

	tglx
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