On Wed, Oct 15, 2014 at 5:57 PM, Sujith Manoharan <sujith@xxxxxxxxxxx> wrote:
> From: Sujith Manoharan <c_manoha@xxxxxxxxxxxxxxxx>
>
> Scan completion for drivers that use HW scanning
> causes a warning to be hit if the interface has been
> removed. Since cfg80211 ensures that both use-after-free
> and scheduling a new scan doesn't happen in this case,
> WARN_ON_ONCE can be used. With ath9k this warning is seen
> many times when multi-channel-concurrency is enabled.
>
> Signed-off-by: Sujith Manoharan <c_manoha@xxxxxxxxxxxxxxxx>
It is not really my business, but how come this happen with ath9k?
The scan should be cancelled before the interface is removed. You mean
that the scan cancellation is
asynchronous and the notification of the cancellation termination can
come after the cfg80211 has removed
the interface?
> ---
> net/wireless/core.c | 2 +-
> net/wireless/scan.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/wireless/core.c b/net/wireless/core.c
> index f52a4cd..2be08e8 100644
> --- a/net/wireless/core.c
> +++ b/net/wireless/core.c
> @@ -931,7 +931,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
> case NETDEV_DOWN:
> cfg80211_update_iface_num(rdev, wdev->iftype, -1);
> if (rdev->scan_req && rdev->scan_req->wdev == wdev) {
> - if (WARN_ON(!rdev->scan_req->notified))
> + if (WARN_ON_ONCE(!rdev->scan_req->notified))
> rdev->scan_req->aborted = true;
> ___cfg80211_scan_done(rdev, false);
> }
> diff --git a/net/wireless/scan.c b/net/wireless/scan.c
> index bda39f1..c0fc0b3 100644
> --- a/net/wireless/scan.c
> +++ b/net/wireless/scan.c
> @@ -239,7 +239,7 @@ void __cfg80211_scan_done(struct work_struct *wk)
> void cfg80211_scan_done(struct cfg80211_scan_request *request, bool aborted)
> {
> trace_cfg80211_scan_done(request, aborted);
> - WARN_ON(request != wiphy_to_rdev(request->wiphy)->scan_req);
> + WARN_ON_ONCE(request != wiphy_to_rdev(request->wiphy)->scan_req);
>
> request->aborted = aborted;
> request->notified = true;
> --
> 2.1.2
>
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