linux-kernel - Re: [PATCH] NFS: Fix RCU warnings in nfs_inode_return_delegation

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Message-ID: <26760.1269903543@redhat.com>
Date:	Mon, 29 Mar 2010 23:59:03 +0100
From:	David Howells <dhowells@...hat.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	dhowells@...hat.com, Eric Dumazet <eric.dumazet@...il.com>,
	Trond.Myklebust@...app.com, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] NFS: Fix RCU warnings in nfs_inode_return_delegation_noreclaim() [ver #2]

Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> Only on Alpha.  Otherwise only a volatile access.

Whilst that is true, it's the principle of the thing.  The extra barrier
shouldn't be emitted on Alpha.  If Alpha's no longer important, then can we
scrap smp_read_barrier_depends()?

My point is that some of these rcu_dereference*()'s are unnecessary.  If
there're required for correctness tracking purposes, fine; but can we have a
macro that is just a dummy for the purpose of stripping the pointer Sparse
annotation?  One that doesn't invoke rcu_dereference_raw() and interpolate a
barrier, pretend or otherwise, when there's no second reference to order
against.

David
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