On Thu, Oct 07, 2010 at 10:34:48AM +0200, Johannes Berg wrote:
> On Wed, 2010-10-06 at 21:13 -0700, Ben Greear wrote:
> > Unless I really screwed up a merge in a strange way, the
> > ieee80211_scan_work is broken.
> >
> > It calls mutex_unlock(&local->mtx) too many times when it hits
> > this code:
> >
> > case SCAN_DECISION:
> > /* if no more bands/channels left, complete scan */
> > if (local->scan_channel_idx >= local->scan_req->n_channels) {
> > aborted = false;
> > goto out_complete;
> > }
>
> So much for trusting Stanislaw :-( I can reproduce this in hwsim.
> Stanislaw, did you ever test software scan at all?
No, sorry.
> Below patch fixes this.
>
> johannes
>
> ---
> net/mac80211/scan.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> --- wireless-testing.orig/net/mac80211/scan.c 2010-10-07 10:27:37.000000000 +0200
> +++ wireless-testing/net/mac80211/scan.c 2010-10-07 10:31:19.000000000 +0200
> @@ -693,8 +693,6 @@ void ieee80211_scan_work(struct work_str
> goto out_complete;
> }
>
> - mutex_unlock(&local->mtx);
> -
> /*
> * as long as no delay is required advance immediately
> * without scheduling a new work
> @@ -725,6 +723,7 @@ void ieee80211_scan_work(struct work_str
> } while (next_delay == 0);
>
> ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
> + mutex_unlock(&local->mtx);
> return;
>
> out_complete:
We never keep locking inside do { } while (next_delay == 0) loop,
perhaps below patch is something better:
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 2c79b83..615a831 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -693,6 +693,7 @@ void ieee80211_scan_work(struct work_struct *work)
case SCAN_DECISION:
/* if no more bands/channels left, complete scan */
if (local->scan_channel_idx >= local->scan_req->n_channels) {
+ mutex_lock(&local->mtx);
aborted = false;
goto out_complete;
}
If so, I will post it officially shortly, if not please proceed
with your patch.
Sorry again
Stanislaw
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