Messages in this thread | | | Date | Wed, 28 Jul 2010 23:00:04 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] cred - synchronize rcu before releasing cred |
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On Wed, Jul 28, 2010 at 01:47:06PM +0100, David Howells wrote: > David Howells <dhowells@redhat.com> wrote: > > > Yeah. I think there are three alternatives: > > There's a fourth alternative too: > > (4) I could try and make it so that if the RCU cleanup routine sees it with a > non-zero usage count, then it just ignores it. This, however, would > require call_rcu() to be able to cope with requeueing.
It is perfectly legal for an RCU callback to invoke call_rcu(). However, this should be used -only- to wait for RCU readers. If there are no RCU readers, the callback might be re-invoked in very short order, expecially on UP systems.
Or am I misunderstanding what you mean by "require call_rcu() to be able to cope iwth requeueing"?
Thanx, Paul
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