Re: [PATCH 3/4] TPM: rcu locking

From: Paul E. McKenney
Date: Thu Sep 25 2008 - 10:34:07 EST


On Thu, Sep 25, 2008 at 08:36:45AM -0500, Serge E. Hallyn wrote:
> Quoting Paul E. McKenney (paulmck@xxxxxxxxxxxxxxxxxx):
> > On Tue, Sep 23, 2008 at 05:18:17PM -0300, Rajiv Andrade wrote:
> > > Paul,
> > >
> > > On Tue, 2008-09-23 at 11:19 -0700, Paul E. McKenney wrote:
> > > >
> > > > But here we are deleting from what appears to be some other list.
> > > > And I don't see any insertiong into either list.
> > > >
> > > > What am I missing here?
> > > >
> > > > Thanx, Paul
> > >
> > > Sorry, forgot to change list_add() to list_add_rcu() in the code section
> > > below:
> > >
> > > > > + /* Make chip available */
> > > > > + spin_lock(&driver_lock);
> > > > > + list_add(&chip->list, &tpm_chip_list);
> > > > > + spin_unlock(&driver_lock);
> > >
> > > I'll resubmit.
> >
> > Cool!
> >
> > So tpm_chip_list and the not-obviously-identical list manipulated
> > in tpm_remove_hardware() really are the same list?
> >
> > Thanx, Paul
>
> Hey Paul,
>
> curious, why do they not look like the same list?

Because one of them is named &tpm_chip_list, a global variable, and the
other seemed to be returned from a function taking a struct device as an
argument. This is indeed consistent with an element in this list being
hung off of the struct device, so perhaps I was just being insufficiently
persistent in tracking things down.

Thanx, Paul
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