linux-kernel - Re: [patch 0/6] rcu head debugobjects

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Message-ID: <20100329133933.GA23238@Krystal>
Date:	Mon, 29 Mar 2010 09:39:33 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, laijs@...fujitsu.com,
	dipankar@...ibm.com, josh@...htriplett.org, dvhltc@...ibm.com,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, adobriyan@...il.com
Subject: Re: [patch 0/6] rcu head debugobjects

Hi Paul,

Thinking about the rcu head init topic, we might be able to drop the
init_rcu_head() initializer. The idea is the following:

- We need init_rcu_head_on_stack()/destroy_rcu_head_on_stack().
- call_rcu() populates the rcu_head and normally does not care about it being
  pre-initialized.
- The activation fixup can detect if a non-initialized rcu head is being
  activated and just perform the fixup without complaining.
- If we have two call_rcu() in a row in the same GP on the same rcu_head, the
  activation check will detect it.

So either we remove all the init_rcu_head(), as was originally proposed, or we
use one that is a no-op on !DEBUG configs and initialize the object with DEBUG
configs.

That removes the dependency on object_is_static().

Thoughts ?

Thanks,

Mathieu


-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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