On 2-1-2017 11:44, Johannes Berg wrote:
>
>> + /*
>> + * allow only one legacy scheduled scan if user-space
>> + * does not indicate multiple scheduled scan support.
>> + */
>> + if (!info->attrs[NL80211_ATTR_SCHED_SCAN_MULTI] &&
>> + cfg80211_legacy_sched_scan_active(rdev))
>> return -EINPROGRESS;
>
> That probably doesn't go far enough - if legacy one is active then we
> probably shouldn't allow a new MULTI one either (or abandon the legacy
> one) so that older userspace doesn't get confused with multiple
> notifications from sched scans it didn't start.
I considered that although not taking the notifications into account.
Will change it. Abandoning the legacy one would be a behavioral change
so probably not acceptable, right?
>> + if (rdev->sched_scan_req_count == rdev->wiphy.max_sched_scan_reqs)
>> + return -ENOSPC;
>
> Do we really want to do the double-accounting, just to avoid counting
> the list length here?
Ok. I have no strong preference.
>> + /* leave request id zero for legacy request */
>
> why? The ID would be ignored, so why special-case it?
It makes the function cfg80211_legacy_sched_scan_active() easier, ie.
not needing a is_legacy flag in struct cfg80211_sched_scan_request.
>> +static void cfg80211_del_sched_scan_req(struct
>> cfg80211_registered_device *rdev,
>> + struct
>> cfg80211_sched_scan_request *req)
>> +{
>> + list_del_rcu(&req->list);
>> + kfree_rcu(req, rcu_head);
>> + synchronize_rcu();
>> + rdev->sched_scan_req_count--;
>> +}
>
> That's bogus - either you use kfree_rcu() or synchronize_rcu() (the
> former is much better); combining both makes no sense.
Thanks. Both functions mentioned the rcu grace period so I was doubtful.
Will change it.
>> +bool cfg80211_legacy_sched_scan_active(struct
>> cfg80211_registered_device *rdev)
>> +{
>> + struct cfg80211_sched_scan_request *req;
>> +
>> + req = list_first_or_null_rcu(&rdev->sched_scan_req_list,
>> + struct
>> cfg80211_sched_scan_request, list);
>> + /* request id 0 indicates legacy request in progress */
>> + return req && !req->reqid;
>> +}
>
> Ok, fair enough.
I guess your remark means this clarifies your earlier question about the
request id, right?
Regards,
Arend
