linux-kernel - Re: [PATCH 1/5] Move sleeping operations to outside the semaphore.

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Date:	Tue, 2 Jun 2009 08:59:23 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] Move sleeping operations to outside the semaphore.

Quoting Tetsuo Handa (penguin-kernel@...ove.sakura.ne.jp):
> TOMOYO is using rw_semaphore for protecting list elements.
> But TOMOYO is doing operations which might sleep inside down_write().
> This patch makes TOMOYO's sleeping operations go outside down_write().
> 
> Signed-off-by: Kentaro Takeda <takedakn@...data.co.jp>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Signed-off-by: Toshiharu Harada <haradats@...data.co.jp>

The overall approach (repeated in each stanza) seems safe enough.
Since there are 3 signed-off-by's, I'll assume you've each studied
each one to make sure there are no little little oopses (i.e.
kfreeing the wrong thing or leaking).  So how about for now I'll
give

Acked-by: Serge Hallyn <serue@...ibm.com>

and when you send a patch with more documentation on Tomoyo, I
will start looking through the locking in more detail and try
to send some patches to standardize it.

Part of why I want to ack this one is it switches to at least
normal kmallocs.  Frankly I'd prefer to skip the rest of the
patchset for now.  Patch 2's been nacked, patch 3 is a lot of
churn for little gain - when a far better patch woudl be one
switching to seq_files.  Patch 4 could in fact be a useful step,
I think.  Patch 5 adds a whole slew of lists that I still don't
like - I'd rather just see a simple patch that adds refcounting
and doesn't do GC yet.

I personally think trying to add GC before standardizing the
locking and refcounting is a bad bad idea.

thanks,
-serge
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