openwrtv3/package/kernel/mac80211/files
Vittorio Gambaletta 8301e61365 mac80211: Fix race condition leading to wifi interfaces not coming up at boot sometimes.
In the drv_mac80211_setup function, mac80211_interface_cleanup
is called to ask the kernel to delete all existing interfaces
for the phy that is being configured via netlink.

Later in the first function, mac80211_prepare_vif is called to
set up the new interfaces as required.

But sometimes, when mac80211_prepare_vif (and so the relevant
`iw phy x interface add y` command) runs, the kernel might still
be cleaning up the old interface with the same ifname. It usually
takes very few time to do that; possibly a few milliseconds of
sleep in the script after detecting this error condition could be
enough, but the busybox sh does not support sub-second sleep
intervals.

When this happens, iw obviously fails to create the new interface;
and the following message is printed in the system log, followed by
subsequent failure messages from hostapd in case this would have been
an AP interface.

Tue Mar 14 04:21:57 2017 daemon.notice netifd: radio1 (2767): command failed: Too many open files in system (-23)

This was a long-standing issue existing since at least OpenWrt Backfire,
and today I finally managed to debug and (hopefully) solve it.
It was happening very few times on most devices; but it was happening
a lot more frequently on fast platforms with multiple radios, such as
the powerpc-based dual-ath9k-radio tl-wdr4900-v1.

Signed-off-by: Vittorio Gambaletta <openwrt@vittgam.net>
2017-03-22 11:42:43 +01:00
..
lib mac80211: Fix race condition leading to wifi interfaces not coming up at boot sometimes. 2017-03-22 11:42:43 +01:00
mac80211.hotplug base-files, mac80211, broadcom-wl: wifi detection and configuration 2016-11-03 11:08:01 +01:00
regdb.txt mac80211: Update wireless-regdb to master-2017-03-07 2017-03-16 11:28:35 +01:00