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Re: [PATCH 2.6 1/5]: Fix locking in __qdisc_destroy rcu-callback

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: [PATCH 2.6 1/5]: Fix locking in __qdisc_destroy rcu-callback
From: Patrick McHardy <kaber@xxxxxxxxx>
Date: Wed, 04 Aug 2004 21:53:28 +0200
Cc: netdev@xxxxxxxxxxx
In-reply-to: <20040804093328.4ee56d30.davem@xxxxxxxxxx>
References: <410FAD44.7020503@xxxxxxxxx> <20040804093328.4ee56d30.davem@xxxxxxxxxx>
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David S. Miller wrote:

On Tue, 03 Aug 2004 17:20:36 +0200
Patrick McHardy <kaber@xxxxxxxxx> wrote:
I'm not sure if RCU callback can be scheduled while the kernel is

running in process context, so this may be unneccessary.

RCU callbacks run via tasklets, and thus in softirq context,
thus your locking changes to _bh() are indeed necessary.
I meant because in my understanding of RCU the quintescent state is
not reached while the CPU is running kernel code, so the callback can't
be scheduled. A previously scheduled callback should finish before
further kernel code is run in process context.


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