linux-kernel - Re: [PATCH] TOMOYO: Use RCU primitives for list operation

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Message-Id: <200912150139.nBF1dXYV065691@www262.sakura.ne.jp>
Date:	Tue, 15 Dec 2009 10:39:33 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	serue@...ibm.com
Cc:	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] TOMOYO: Use RCU primitives for list operation

Hello.

Serge E. Hallyn wrote:
> Just out of curiosity (and bc I'm personally much more familiar with plain old
> rcu), I assume you have a list of places where sleeping under rcu is necessary
> or greatly simplifies/cleans up the code?

Yes.

TOMOYO checks operations which are permitted to sleep so that we can load
policy like call_usermodehelper("/sbin/modprobe"). I tried to use non-sleeping
RCU while implementing garbage collector support. But that attempt resulted in
messing up the code with full of atomic_inc()/atomic_dec() calls.
Thus, I decided to use sleeping RCU.

I tested garbage collector support using sleeping RCU with non-LSM version of
TOMOYO. It is working well. Thus, I started breaking non-LSM version of TOMOYO
into smaller pieces and proposing for LSM version of TOMOYO.

Thank you for reviewing. I'll send next patches.
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