linux-kernel - Re: [PATCH] move put_task_struct() reaping into a thread [Re: 2.6.18-rt1]

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Date:	Wed, 27 Sep 2006 02:14:56 -0700
From:	Bill Huey (hui) <billh@...ppy.monkey.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Bill Huey (hui)" <billh@...ppy.monkey.org>
Subject: Re: [PATCH] move put_task_struct() reaping into a thread [Re: 2.6.18-rt1]

On Wed, Sep 27, 2006 at 10:57:12AM +0200, Ingo Molnar wrote:
> * Bill Huey <billh@...ppy.monkey.org> wrote:
> 
> > Because the conversion of memory allocation routines like kmalloc and 
> > kfree aren't safely callable within a preempt_disable critical section 
> > since they were incompletely converted in the -rt. [...]
> 
> they were not 'incompletely converted' - they are /intentionally/ fully 
> preemptible.

What I meant by "incompletely converted" is that the allocators could be
made more safe in non-preemptible scenarios under -rt. It's potentially
a valuable thing to have since GFP_ATOMIC semantics already exist in the
current allocators and a newer category could be added as a new feature of
that allocator for those scenarios. I'm happy dequeuing things off of my
own free list, but that's just me.

-rt semanatics created a couple of new locking scenarios that the previous
kernel didn't really have to address. That's all that I meant by that. :)

bill

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