Re: [PATCH] mac80211: check whether scan is in progress before queueing scan_work

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2010-04-06 at 11:54 +0300, Teemu Paasikivi wrote:
> As scan_work is queued from work_work it needs to be checked if scan
> has been started during execution of work_work. Otherwise, when hw
> scan is used, the stack gets error about hw being busy with ongoing
> scan. This causes the stack to abort scan without notifying the driver
> about it. This leads to a situation where the hw is scanning and the stack
> thinks it's not. Then when the scan finishes, the stack will complain by
> warnings.

Actually, let's go with this patch. It should solve both Luis's and your
problem, and I just reviewed the locking -- currently scan_mtx and
work_mtx are completely independent.

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>

> Signed-off-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
> ---
>  net/mac80211/work.c |    7 ++++++-
>  1 files changed, 6 insertions(+), 1 deletions(-)
> 
> diff --git a/net/mac80211/work.c b/net/mac80211/work.c
> index 1e1ea30..7bd8670 100644
> --- a/net/mac80211/work.c
> +++ b/net/mac80211/work.c
> @@ -919,11 +919,16 @@ static void ieee80211_work_work(struct work_struct *work)
>  		run_again(local, jiffies + HZ/2);
>  	}
>  
> -	if (list_empty(&local->work_list) && local->scan_req)
> +	mutex_lock(&local->scan_mtx);
> +
> +	if (list_empty(&local->work_list) && local->scan_req &&
> +	    !local->scanning)
>  		ieee80211_queue_delayed_work(&local->hw,
>  					     &local->scan_work,
>  					     round_jiffies_relative(0));
>  
> +	mutex_unlock(&local->scan_mtx);
> +
>  	mutex_unlock(&local->work_mtx);
>  
>  	ieee80211_recalc_idle(local);