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Subject: Re: Why can't I set the priority of softirq-hrt? (Re: 2.6.17-rt1)
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Esben Nielsen <nielsen.esben@googlemail.com>
Cc: Esben Nielsen <nielsen.esben@gogglemail.com>,
       Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
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Date: Thu, 22 Jun 2006 09:06:12 +0200
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On Thu, 2006-06-22 at 00:35 +0100, Esben Nielsen wrote:
> On Wed, 21 Jun 2006, Thomas Gleixner wrote:
> 
> > On Wed, 2006-06-21 at 22:29 +0100, Esben Nielsen wrote:
> >>> Find an version against the code in -mm below. Not too much tested yet.
> >>
> >> What if setscheduler is called from interrup context as in the hrt timers?
> >
> > It simply gets stuff going, nothing else.
> >
> What I mean is that we will then do the full priority inheritance boost 
> with interrupts off.

Only in the case when its called from IRQ context.

> Before setscheduler() was O(1), now it is O(<lock depth of what ever lock 
> the target task might be locked on>).
>
> This is not a problem for your use of setscheduler() as the task involved 
> only can be blocked on kernel mutexes, but when the function is used on a 
> userspace process the lock depth can be deep.

Damn, I missed that this is still in the irq off section, when called
from do_sched_setscheduler().

Good catch. I fix that.

	tglx