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

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Message-ID: <26510.1270582446@redhat.com>
Date:	Tue, 06 Apr 2010 20:34:06 +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:

> OK, just to make sure I understand you...  You are asking for two additional
> RCU API members:
> 
> 1.	rcu_access_pointer() or some such that includes ACCESS_ONCE(),
> 	but not smp_read_barrier_depends(), which may be used when
> 	we are simply examining the value of the RCU-protected pointer
> 	(as in the NFS case).  It could also be used when the
> 	appropriate update-side lock is held, but for that we have:
> 
> 2.	rcu_dereference_protected() or some such that includes neither
> 	ACCESS_ONCE() nor smp_read_barrier_depends(), and that may
> 	only be used if updates are prevented, for example, by holding
> 	the appropriate update-side lock.
> 
> Does this fit?

Yep.  I think so.

David
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