On Tue, 2016-08-30 at 14:39 +0300, Amir Vadai wrote:
> On Tue, Aug 30, 2016 at 02:03:08PM +0300, Amir Vadai wrote:
> > Regarding the specific action in this patchset, correct me if I'm wrong,
> > but I think that the lock could be removed safely.
Sure ;)
> >
> > When the action is modified during traffic, an existing tcf_enc_metadata
> > is not changed, but a new metadata is allocated and the pointer is
> > replaced to point to the new one.
> > I just need to make sure that when changing an action from 'release'
> > into 'set' - tcf_enc_metadata will be set before the action type is
> > changed - change the order of operations and add a memory barrier.
> > Here is a pseudo code to explain:
> >
> > metadata_new = new allocated metadata
> > metadata_old = t->tcft_enc_metadata
> >
>
> Oh - I had a typo here:
> Need to set the metadata and only after that, set the action:
>
> t->tcft_enc_metadata = metadata_new
> wmb()
rcu_assign_pointer() is your friend, it auto documents the thing.
Note that you probably need to store in the allocated object :
dst,
tcf_action (a copy of it, read in tunnel_key_act()
tcft_action ( a copy of it, read in tunnel_key_act())
rcu_head rcu for kfree_rcu()
> t->tcft_action = encapdecap
>
> > t->tcft_action = encapdecap
> >
> > /* make sure the compiler won't swap the setting of tcft_action with
> > * tcft_enc_metadata
> > */
> > wmb()
> >
> > t->tcft_enc_metadata = metadata_new
> > release metadata_old
> >
> >
> > This way, no need for lock between the init() and act() operations.
> >
> > Please let me know if you see a problem with this approach.
> > I will also change the stats to be percpu.
Right, check tcf_hash_create() last argument. (false -> true)
Thanks.
