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Subject: Re: iwlist scanning: how to exclude old scan results from output?
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Bruno Dantas <wireless@dantas.airpost.net>,
        linux-wireless@vger.kernel.org
Date:   Fri, 29 May 2020 09:44:35 +0200
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On Thu, 2020-05-28 at 15:06 -0400, Bruno Dantas wrote:
> > That's why 'flush' exists :)
> Alas, mine seems to be clogged :)

Evidently :)

> > Obviously. But still, now I'm wondering if there's a bug?
> > What driver are you using?
> My adapter is  Atheros AR928X  which uses the  ath9k  driver.

Hm. That should be fine.

Well, I don't know. It's weird because the timeout and flush are
basically exactly the same thing!

If you want to debug it, I guess you could start with something like
this:

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 74ea4cfb39fb..6fe609f6cd0e 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -483,6 +483,7 @@ void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev,
 	if (!request->info.aborted &&
 	    request->flags & NL80211_SCAN_FLAG_FLUSH) {
 		/* flush entries from previous scans */
+		printk(KERN_DEBUG "flushing at %ld, start was %ld\n", jiffies, request->scan_start);
 		spin_lock_bh(&rdev->bss_lock);
 		__cfg80211_bss_expire(rdev, request->scan_start);
 		spin_unlock_bh(&rdev->bss_lock);

Unless maybe it got into the aborted case?

Maybe before you even do this, run "iw event -t" while doing the scan
with flush.

johannes