linux-kernel - Re: Pin-pointing the root of unusual application latencies

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Message-Id: <200707251831.34969.fzu@wemgehoertderstaat.de>
Date:	Wed, 25 Jul 2007 18:31:34 +0200
From:	Karsten Wiese <fzu@...gehoertderstaat.de>
To:	John Sigler <linux.kernel@...e.fr>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-rt-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Pin-pointing the root of unusual application latencies

Am Mittwoch, 25. Juli 2007 schrieb John Sigler:
> Karsten Wiese wrote:
> 
> > John Sigler wrote:
> > 
> >> Is there some form of priority inheritance? Does the IRQ handler get a 
> >> priority boost if a high priority task is waiting for it?
> > 
> > No. But that would be "nice to have".
> 
> No to the first question? to the second question? or to both? :-)
> 
To the second.
I checked some soundcard drivers some time ago in -rt kernels, looking for
that "priority boosted by consuming process threaded interrupt handler".
Then there was no such.

> In kernel/futex.c does "PI" stand for Priority Inheritance?
> 
I guess so, yes.

> e.g.
> 
> /*
>   * Priority Inheritance state:
>   */
> struct futex_pi_state {
> 	/*
> 	 * list of 'owned' pi_state instances - these have to be
> 	 * cleaned up in do_exit() if the task exits prematurely:
> 	 */
> 	struct list_head list;
> 
> 	/*
> 	 * The PI object:
> 	 */
> 	struct rt_mutex pi_mutex;
> 
> 	struct task_struct *owner;
> 	atomic_t refcount;
> 
> 	union futex_key key;
> };
> 
> 


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