cfg80211: make spurious warnings less likely, configurable

Bob reported that he got warnings in IBSS mode about
the ssid_len being zero on a joined event, but only
when kmemcheck was enabled. This appears to be due
to a race condition between drivers and userspace,
when the driver reports joined but the user in the
meantime decided to leave the IBSS again, the warning
would trigger. This was made more likely by kmemcheck
delaying the code that does the check and sends the
event.

So first, make the warning trigger closer to the
driver, which means it's not locked, but since only
the warning depends on it that's ok.

And secondly, users will not want to have spurious
warnings at all, so make those that are known to be
racy in such a way configurable.

Reported-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/net/wireless/Kconfig b/net/wireless/Kconfig
index c6031d5b135f..aea7e6824af9 100644
--- a/net/wireless/Kconfig
+++ b/net/wireless/Kconfig
@@ -17,6 +17,23 @@ config NL80211_TESTMODE
 
           Say N.
 
+config CFG80211_DEVELOPER_WARNINGS
+        bool "enable developer warnings"
+        depends on CFG80211
+        default n
+        help
+          This option enables some additional warnings that help
+          cfg80211 developers and driver developers, but that can
+          trigger due to races with userspace.
+
+          For example, when a driver reports that it was disconnected
+          from the AP, but the user disconnects manually at the same
+          time, the warning might trigger spuriously due to races.
+
+          Say Y only if you are developing cfg80211 or a driver based
+          on it (or mac80211).
+
+
 config CFG80211_REG_DEBUG
         bool "cfg80211 regulatory debugging"
         depends on CFG80211