On 10 March 2014 09:32, Eliad Peller <eliad@xxxxxxxxxx> wrote:
> On Mon, Mar 10, 2014 at 9:37 AM, Luciano Coelho
> <luciano.coelho@xxxxxxxxx> wrote:
>> On Sun, 2014-03-09 at 17:13 +0200, Eliad Peller wrote:
>>> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@xxxxxxxxx> wrote:
>>> > With single-channel drivers, we need to be able to change a running
>>> > chanctx if we want to use chanctx reservation. Not all drivers may be
>>> > able to do this, so add a flag that indicates support for it.
>>> >
>>> > Changing a running chanctx can also be used as an optimization in
>>> > multi-channel drivers when the context needs to be reserved for future
>>> > usage.
>>> >
>>> > Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
>>> > reserved so nobody else can use it (since we know it's going to
>>> > change). In the future, we may allow several vifs to use the same
>>> > reservation as long as they plan to use the chanctx on the same
>>> > future channel.
>>> >
>>> > Signed-off-by: Luciano Coelho <luciano.coelho@xxxxxxxxx>
>>> > ---
>>> [...]
>>>
>>> > @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
>>> > list_for_each_entry(ctx, &local->chanctx_list, list) {
>>> > const struct cfg80211_chan_def *compat;
>>> >
>>> > - if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
>>> > + /* We don't support chanctx reservation for multiple
>>> > + * vifs yet, so don't allow reserved chanctxs to be
>>> > + * reused.
>>> > + */
>>> > + if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
>>> > + ieee80211_chanctx_is_reserved(local, ctx))
>>> > continue;
>>> >
>>> i'm not sure that's correct.
>>> you might want to find a chanctx in order to use it, not only for
>>> reservation. any reason to reject it in this case?
>>
>> At the moment we don't support multi-vifs switching at the same time, so
>> we don't allow anyone else to use a chanctx while it's reserved.
>>
> i'm not talking about multi-vifs switching.
> consider the following scenario:
> sta connected on channel 40
> ap beaconing on channel 60
>
> now, you want (for whatever reason) to switch the ap to channel 40.
> you'll reserve the sta's chanctx, and increase its refcount (to 2).
>
> now a new sta vif is added, and tries to connect on channel 40.
> the check above will skip the existing channel context (because it's
> also reserved) although there is no reason it won't be used.
Good point. I have this case covered in my multi-vif csa patches. We
could transplant it into Luca's patch?
Michał
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