svn commit: r224654 - user/adrian/if_ath_tx/sys/dev/ath

[Adrian Chadd]

Author: adrian
Date: Fri Aug  5 06:57:44 2011
New Revision: 224654
URL: http://svn.freebsd.org/changeset/base/224654

Log:
  Flip back to having the TXQ lock held during the whole of ath_tx_processq().
  I'll deal with correcting the locking later so LORs don't occur.
  For now, this will let me write TX packet completion functions to implement
  BAW tracking and aggregation, which will update per-TID state.
  
  Having the TXQ locked in this way means that:
  
  (a) the order of TXQ completions being processed will be correct - ie, multiple
      concurrent calls to ath_tx_processq() for the same TXQ won't mess things up;
  (b) the per-TID state is correctly locked, so concurrent TX scheduling and
      TX completion isn't going to end up with subtle race conditions.
  
  As long as completions are only ever called from ath_tx_proc(), this should
  be fine - it won't race with itself. The race conditions are what I'm worried
  about.

Modified:
  user/adrian/if_ath_tx/sys/dev/ath/if_ath.c

Modified: user/adrian/if_ath_tx/sys/dev/ath/if_ath.c
==============================================================================
--- user/adrian/if_ath_tx/sys/dev/ath/if_ath.c	Thu Aug  4 17:17:57 2011	(r224653)
+++ user/adrian/if_ath_tx/sys/dev/ath/if_ath.c	Fri Aug  5 06:57:44 2011	(r224654)
@@ -4139,17 +4139,16 @@ ath_tx_processq(struct ath_softc *sc, st
 	int nacked;
 	HAL_STATUS status;
 
+	ATH_TXQ_LOCK(txq);
 	DPRINTF(sc, ATH_DEBUG_TX_PROC, "%s: tx queue %u head %p link %p\n",
 		__func__, txq->axq_qnum,
 		(caddr_t)(uintptr_t) ath_hal_gettxbuf(sc->sc_ah, txq->axq_qnum),
 		txq->axq_link);
 	nacked = 0;
 	for (;;) {
-		ATH_TXQ_LOCK(txq);
 		txq->axq_intrcnt = 0;	/* reset periodic desc intr count */
 		bf = STAILQ_FIRST(&txq->axq_q);
 		if (bf == NULL) {
-			ATH_TXQ_UNLOCK(txq);
 			break;
 		}
 		ds0 = &bf->bf_desc[0];
@@ -4162,7 +4161,6 @@ ath_tx_processq(struct ath_softc *sc, st
 			    status == HAL_OK);
 #endif
 		if (status == HAL_EINPROGRESS) {
-			ATH_TXQ_UNLOCK(txq);
 			break;
 		}
 		ATH_TXQ_REMOVE_HEAD(txq, bf_list);
@@ -4179,7 +4177,6 @@ ath_tx_processq(struct ath_softc *sc, st
 		if (txq->axq_depth == 0)
 #endif
 			txq->axq_link = NULL;
-		ATH_TXQ_UNLOCK(txq);
 
 		ni = bf->bf_node;
 		/*
@@ -4226,14 +4223,6 @@ ath_tx_processq(struct ath_softc *sc, st
 #endif
 
 	/* Kick the TXQ scheduler */
-	/*
-	 * We can't hold the TXQ lock across the completion function;
-	 * the IEEE80211_NODE_LOCK is likely going to be held there
-	 * during buffer/node free. It's up to the completion
-	 * function to grab the TXQ lock before updating TID state
-	 * (eg sliding the BAW along.)
-	 */
-	ATH_TXQ_LOCK(txq);
 	ath_txq_sched(sc, txq);
 	ATH_TXQ_UNLOCK(txq);