linux-kernel - Re: [TOMOYO 05/15](repost) Domain transition handler functions.

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Message-ID: <470395B3.2020904@kaigai.gr.jp>
Date:	Wed, 03 Oct 2007 22:14:27 +0900
From:	KaiGai Kohei <kaigai@...gai.gr.jp>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
CC:	jmorris@...ei.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, chrisw@...s-sol.org
Subject: Re: [TOMOYO 05/15](repost) Domain transition handler functions.

Tetsuo Handa wrote:
> James Morris wrote:
>> I'm pretty sure that the singly linked list idea has been rejected a few 
>> times.  Just use the existing API.
> Too bad...
> 
> Well, is there a way to avoid read_lock when reading list?
> 
> Currently, TOMOYO Linux avoids read_lock, on the assumption that
> (1) First, ptr->next is initialized with NULL.
> (2) Later, ptr->next is assigned non-NULL address.
> (3) Assigning to ptr->next is done atomically.
> 
> Regards.

Is it all of the purpose for the list structure?
If so, you can apply RCU instead to avoid read lock
when scanning the list, like:

rcu_read_lock();
list_for_each_entry(...) {
     ....
}
rcu_read_unlock();

-- 
KaiGai Kohei <kaigai@...gai.gr.jp>
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