Re: Setting the priority of an IRQ thread - Uwe Kleine-König

From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Martin Shepherd <mcs@astro.caltech.edu>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: Setting the priority of an IRQ thread
Date: Tue, 16 Jun 2009 20:27:34 +0200	[thread overview]
Message-ID: <20090616182734.GD13048@pengutronix.de> (raw)
In-Reply-To: <loom.20090616T074347-549@post.gmane.org>

On Tue, Jun 16, 2009 at 07:59:28AM +0000, Martin Shepherd wrote:
> Suresh Kumar SHUKLA <suresh.shukla <at> st.com> writes:
> > 	// get IRQ descriptor from IRQ, it contains pid
> > 	desc = &irq_desc[IRQ_BASIC_TIMER_3_1];
> 
> That's a very useful clue. I was thinking that I would have to walk the process
> tree to find the thread by name. Following up on this clue, it appears as though
> in kernel 2.6.29.4 I should be able to use desc=irq_to_desc(irq) to look up the
> IRQ descriptor, then use pid=get_task_pid(desc->thread), to get the PID of the
> IRQ thread, then use sys_sched_setscheduler(pid,...) to change its priority.
> I'll try that out in the morning.
I wouldn't recommend calling sys_sched_setscheduler from kernel space.
That's the userspace API and you need to pass a __user pointer as third
argument.

The right way is to do this change from userspace.

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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