On Wed, Mar 18, 2015 at 06:18:53PM +0300, Evgeniy Polyakov wrote:
> Hi
>
> 18.03.2015, 07:20, "David Fries" <da...@fries.net>:
> > static void w1_therm_remove_slave(struct w1_slave *sl)
> > {
> > + int refcnt = atomic_sub_return(1, THERM_REFCNT(sl->family_data));
> > + while(refcnt) {
> > + msleep(1000);
> > + refcnt = atomic_read(THERM_REFCNT(sl->family_data));
> > + }
> > kfree(sl->family_data);
> > sl->family_data = NULL;
> > }
>
> Can we replace this whole atomic manipulations with kref_t and free family
> data in the place
> which actually drops reference counter to zero?
>
> I.e. we return from remove_slave() function potentially leaving family data
> floating around, it will be freed
> when the last user drops the reference. There is still a race between
> increasing reference when starting
> reading and removing slave device, i.e. one starts reading, while attached
> slave device is being removed,
> but that's a different problem.
With the two while loops I posted, I see with two clients reading
w1_slave, the other command to remove a slave gets permanently stuck
in w1_therm_remove_slave, which keeps the slave around while the
clients continue to read. I wouldn't predict things going better by
keeping family_data around longer, the slave data would still go away
with readers around.
--
David Fries <da...@fries.net> PGP pub CB1EE8F0
http://fries.net/~david/
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