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SubjectRe: [PATCH 3/4] TPM: rcu locking
Quoting Paul E. McKenney (paulmck@linux.vnet.ibm.com):
> On Thu, Sep 25, 2008 at 08:36:45AM -0500, Serge E. Hallyn wrote:
> > Quoting Paul E. McKenney (paulmck@linux.vnet.ibm.com):
> > > 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

Right, tpm_register_hardware both does
dev_set_drvdata(dev, chip)
to set dev->driver_data = chip, and list_add(chip->list, &tpm_chip_list).
The tpm_remove_hardware(), then, gets the device, gets the chip from
dev->driver_data, and removes it from the tpm_chip_list.

It does look kosher.

Though once this is all applied to some public git tree, I want to take
some time to look at the full result.

-serge


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