Messages in this thread | | | Date | Mon, 13 Mar 2006 08:34:53 +0530 | From | "Balbir Singh" <> | Subject | Re: [patch 1/3] radix tree: RCU lockless read-side |
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On 3/11/06, Nick Piggin <nickpiggin@yahoo.com.au> wrote: > Balbir Singh wrote: > > <snip> > > > >> if (slot->slots[i]) { > >>- results[nr_found++] = slot->slots[i]; > >>+ results[nr_found++] = &slot->slots[i]; > >> if (nr_found == max_items) > >> goto out; > >> } > > > > > > A quick clarification - Shouldn't accesses to slot->slots[i] above be > > protected using rcu_derefence()? > > > > I think we're safe here -- this is the _address_ of the pointer. > However, when dereferencing this address in _gang_lookup, > I think we do need rcu_dereference indeed. >
Yes, I saw the address operator, but we still derefence "slots" to get the address.
> Note that _gang_lookup_slot doesn't do this for us, however -- > the caller must do that when dereferencing the pointer to the > item (eg. see page_cache_get_speculative in 2/3).
Oh! I did not get that far. Will look at the rest of the series
> > That said, I'm not 100% sure I have the rcu memory barriers in > the right places (well I'm sure I don't, given the _gang_lookup > bug you exposed!).
Hmm... Let me look at rcu_torture module and see if I can figure it out or read the documentation again.
> > Thanks, > Nick >
Warm Regards, Balbir - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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