linux-kernel - Re: 2.6.23-rc6-mm1: IPC: sleeping function called ...

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Date:	Tue, 18 Sep 2007 21:41:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nadia Derbey <Nadia.Derbey@...l.net>,
	Alexey Dobriyan <adobriyan@...ru>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: 2.6.23-rc6-mm1: IPC: sleeping function called ...

On Tue, 18 Sep 2007 11:29:24 -0700 "Paul E. McKenney"
<paulmck@...ux.vnet.ibm.com> wrote:

> On Tue, Sep 18, 2007 at 09:57:15AM -0700, Andrew Morton wrote:
> > On Tue, 18 Sep 2007 09:13:37 -0700 "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> > 
> > > On Tue, Sep 18, 2007 at 02:24:51PM +0200, Peter Zijlstra wrote:
> > > > On Tue, 18 Sep 2007 03:34:00 -0700 Andrew Morton
> > > > <akpm@...ux-foundation.org> wrote:
> > > > 
> > > > > Well, it was an optimisation.  spin_lock() implies rcu_read_lock().  That's
> > > > > a bit dirty and we might choose to not do that.
> > > > 
> > > > Not true for the preemptible-rcu work. All such sites should be fixed,
> > > > or at the very least heavily annotated.
> > > 
> > > What he said!!!
> > > 
> > 
> > What he said!
> > 
> > How are you going to find all such sites?
> 
> A first step would be to look for patches in -rt that add rcu_read_lock()
> or friends.  A second step would be to look for rcu_dereference() without
> an enclosing rcu_read_lock(), rcu_read_lock_bh(), or preempt_disable().

I could perhaps do that with that rcu_read_lock lockdep annotation. If
I add a check for holding rcu_read_lock in rcu_dereference().
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