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571aedbc6c
Improve performance and fix potential mgmt tx hangs/warnings Signed-off-by: Felix Fietkau <nbd@nbd.name>
62 lines
2.2 KiB
Diff
62 lines
2.2 KiB
Diff
From: Johannes Berg <johannes.berg@intel.com>
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Date: Tue, 23 Mar 2021 21:05:01 +0100
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Subject: [PATCH] mac80211: fix TXQ AC confusion
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Normally, TXQs have
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txq->tid = tid;
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txq->ac = ieee80211_ac_from_tid(tid);
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However, the special management TXQ actually has
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txq->tid = IEEE80211_NUM_TIDS; // 16
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txq->ac = IEEE80211_AC_VO;
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This makes sense, but ieee80211_ac_from_tid(16) is the same
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as ieee80211_ac_from_tid(0) which is just IEEE80211_AC_BE.
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Now, normally this is fine. However, if the netdev queues
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were stopped, then the code in ieee80211_tx_dequeue() will
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propagate the stop from the interface (vif->txqs_stopped[])
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if the AC 2 (ieee80211_ac_from_tid(txq->tid)) is marked as
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stopped. On wake, however, __ieee80211_wake_txqs() will wake
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the TXQ if AC 0 (txq->ac) is woken up.
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If a driver stops all queues with ieee80211_stop_tx_queues()
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and then wakes them again with ieee80211_wake_tx_queues(),
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the ieee80211_wake_txqs() tasklet will run to resync queue
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and TXQ state. If all queues were woken, then what'll happen
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is that _ieee80211_wake_txqs() will run in order of HW queues
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0-3, typically (and certainly for iwlwifi) corresponding to
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ACs 0-3, so it'll call __ieee80211_wake_txqs() for each AC in
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order 0-3.
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When __ieee80211_wake_txqs() is called for AC 0 (VO) that'll
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wake up the management TXQ (remember its tid is 16), and the
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driver's wake_tx_queue() will be called. That tries to get a
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frame, which will immediately *stop* the TXQ again, because
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now we check against AC 2, and AC 2 hasn't yet been marked as
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woken up again in sdata->vif.txqs_stopped[] since we're only
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in the __ieee80211_wake_txqs() call for AC 0.
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Thus, the management TXQ will never be started again.
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Fix this by checking txq->ac directly instead of calculating
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the AC as ieee80211_ac_from_tid(txq->tid).
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Fixes: adf8ed01e4fd ("mac80211: add an optional TXQ for other PS-buffered frames")
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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---
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--- a/net/mac80211/tx.c
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+++ b/net/mac80211/tx.c
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@@ -3589,7 +3589,7 @@ begin:
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test_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags))
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goto out;
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- if (vif->txqs_stopped[ieee80211_ac_from_tid(txq->tid)]) {
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+ if (vif->txqs_stopped[txq->ac]) {
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set_bit(IEEE80211_TXQ_STOP_NETIF_TX, &txqi->flags);
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goto out;
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}
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