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Re: [Xen-devel] [PATCH] remove redundant rcu_read_unlock

To: <ncmike@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] remove redundant rcu_read_unlock
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 28 Mar 2007 20:22:37 +0100
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On 28/3/07 20:06, "Mike D. Day" <ncmike@xxxxxxxxxx> wrote:

> In the function rcu_lock_domain_by_id there is a call to
> rcu_read_unlock just prior to returning. However, the intent is that
> the rcu reader retain the read lock after the call has returned. This
> can be verified by auditing the callers of this routine, which each
> explicitly call rcu_unlock_domain, which in turn calls
> rcu_read_unlock.
> --
> Remove redundant call to rcu_read_unlock.

It's not redundant -- that's the error path (returning NULL). Callers do not
call the unlock function in this case.

 -- Keir

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