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commit1153a74768upstream. Normally, TXQs have txq->tid = tid; txq->ac = ieee80211_ac_from_tid(tid); However, the special management TXQ actually has txq->tid = IEEE80211_NUM_TIDS; // 16 txq->ac = IEEE80211_AC_VO; This makes sense, but ieee80211_ac_from_tid(16) is the same as ieee80211_ac_from_tid(0) which is just IEEE80211_AC_BE. Now, normally this is fine. However, if the netdev queues were stopped, then the code in ieee80211_tx_dequeue() will propagate the stop from the interface (vif->txqs_stopped[]) if the AC 2 (ieee80211_ac_from_tid(txq->tid)) is marked as stopped. On wake, however, __ieee80211_wake_txqs() will wake the TXQ if AC 0 (txq->ac) is woken up. If a driver stops all queues with ieee80211_stop_tx_queues() and then wakes them again with ieee80211_wake_tx_queues(), the ieee80211_wake_txqs() tasklet will run to resync queue and TXQ state. If all queues were woken, then what'll happen is that _ieee80211_wake_txqs() will run in order of HW queues 0-3, typically (and certainly for iwlwifi) corresponding to ACs 0-3, so it'll call __ieee80211_wake_txqs() for each AC in order 0-3. When __ieee80211_wake_txqs() is called for AC 0 (VO) that'll wake up the management TXQ (remember its tid is 16), and the driver's wake_tx_queue() will be called. That tries to get a frame, which will immediately *stop* the TXQ again, because now we check against AC 2, and AC 2 hasn't yet been marked as woken up again in sdata->vif.txqs_stopped[] since we're only in the __ieee80211_wake_txqs() call for AC 0. Thus, the management TXQ will never be started again. Fix this by checking txq->ac directly instead of calculating the AC as ieee80211_ac_from_tid(txq->tid). Fixes:adf8ed01e4("mac80211: add an optional TXQ for other PS-buffered frames") Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/r/20210323210500.bf4d50afea4a.I136ffde910486301f8818f5442e3c9bf8670a9c4@changeid Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.