netdev - Re: [PATCH] niu: fix SMP race protecting rx_rings and tx

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Message-Id: <20110203.152214.59684545.davem@davemloft.net>
Date:	Thu, 03 Feb 2011 15:22:14 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	fleitner@...hat.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] niu: fix SMP race protecting rx_rings and tx_rings

From: Flavio Leitner <fleitner@...hat.com>
Date: Thu, 3 Feb 2011 21:18:05 -0200

> Ok, I can write a new version using RCU if you like.

Don't worry, I'll take care of it, I actually have the
hardware to test on :-)

> I've chose rwsem because I think those operations aren't
> frequent. The RCU leaves an operation to run later during
> a safe context, so I thought the cost doesn't worth it.

One thing I'm worried about with your patch is that the statistics
method can be called in basically any context, therefore a sleeping
lock like the rw_semaphore is probably not usable.

In fact I'm going to revert your patch for now because of this issue.
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