path: root/fs
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authorEmmanuel Grumbach <>2011-11-27 15:29:44 +0200
committerGreg Kroah-Hartman <>2011-12-09 08:54:28 -0800
commitf06b70aa96019273ed984f76c79ad786ac216f7e (patch)
tree89d859582756724cf3b663c26445cffa4aa31f27 /fs
parent743646bb5669b390e18a7d1f45ab5db8db48e09d (diff)
mac80211: fix race between the AGG SM and the Tx data path
commit 2a1e0fd175dcfd72096ba9291d31e3b1b5342e60 upstream. When a packet is supposed to sent be as an a-MPDU, mac80211 sets IEEE80211_TX_CTL_AMPDU to let the driver know. On the other hand, mac80211 configures the driver for aggregration with the ampdu_action callback. There is race between these two mechanisms since the following scenario can occur when the BA agreement is torn down: Tx softIRQ drv configuration ========== ================= check OPERATIONAL bit Set the TX_CTL_AMPDU bit in the packet clear OPERATIONAL bit stop Tx AGG Pass Tx packet to the driver. In that case the driver would get a packet with TX_CTL_AMPDU set although it has already been notified that the BA session has been torn down. To fix this, we need to synchronize all the Qdisc activity after we cleared the OPERATIONAL bit. After that step, all the following packets will be buffered until the driver reports it is ready to get new packets for this RA / TID. This buffering allows not to run into another race that would send packets with TX_CTL_AMPDU unset while the driver hasn't been requested to tear down the BA session yet. This race occurs in practice and iwlwifi complains with a WARN_ON when it happens. Signed-off-by: Emmanuel Grumbach <> Reviewed-by: Johannes Berg <> Signed-off-by: John W. Linville <> Signed-off-by: Greg Kroah-Hartman <>
Diffstat (limited to 'fs')
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