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

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Date:	Thu, 21 Sep 2006 14:56:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Esben Nielsen <nielsen.esben@...glemail.com>
Cc:	Bill Huey <billh@...ppy.monkey.org>, 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>,
	Esben Nielsen <simlo@...s.au.dk>
Subject: Re: [PATCH] move put_task_struct() reaping into a thread [Re: 2.6.18-rt1]

* Esben Nielsen <nielsen.esben@...glemail.com> wrote:

> The whole point is to defer those frees to a task. In -rt call_rcu() 
> is abused to do that in the case of put_task_struct(). But it is abuse 
> since call_rcu() is much more resourcefull than simply defering to a 
> task.

nah, it's not nearly as "resourceful" as having a separate thread for 
each teardown type ... It is also the easiest to maintain way of tearing 
down stuff, so i'm quite happy with it. If then i'll move the mm_struct 
teardown to RCU too. (Later on we can do some 'fastpath RCU' thing 
perhaps, to force an RCU batch of work through quiescent state)

but this is quite likely a side-issue that probably has no connection to 
the crash Bill was seeing. Whether separate teardown thread or 
softirq-rcu, it's a separate thread already.

	Ingo
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