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Date:      Tue, 8 Nov 2011 21:13:05 +0000 (UTC)
From:      Adrian Chadd <adrian@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r227359 - head/sys/dev/ath
Message-ID:  <201111082113.pA8LD5Dd049423@svn.freebsd.org>
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Author: adrian
Date: Tue Nov  8 21:13:05 2011
New Revision: 227359
URL: http://svn.freebsd.org/changeset/base/227359

Log:
  Change ath_buf allocation to:
  
  * Immediately return NULL if a buffer isn't available;
  * Track the "buffers not available" count;
  * Clear some fields used for tx aggregation;
  * Add ath_buf_clone() which clones the majority of buffer state.
    This is needed when retransmission of a "busy" buffer is required.
  
  Sponsored by:	Hobnob, Inc.

Modified:
  head/sys/dev/ath/if_ath.c
  head/sys/dev/ath/if_ath_misc.h

Modified: head/sys/dev/ath/if_ath.c
==============================================================================
--- head/sys/dev/ath/if_ath.c	Tue Nov  8 21:06:36 2011	(r227358)
+++ head/sys/dev/ath/if_ath.c	Tue Nov  8 21:13:05 2011	(r227359)
@@ -1890,18 +1890,89 @@ _ath_getbuf_locked(struct ath_softc *sc)
 	ATH_TXBUF_LOCK_ASSERT(sc);
 
 	bf = TAILQ_FIRST(&sc->sc_txbuf);
+	if (bf == NULL) {
+		sc->sc_stats.ast_tx_getnobuf++;
+	} else {
+		if (bf->bf_flags & ATH_BUF_BUSY) {
+			sc->sc_stats.ast_tx_getbusybuf++;
+			bf = NULL;
+		}
+	}
+
 	if (bf != NULL && (bf->bf_flags & ATH_BUF_BUSY) == 0)
 		TAILQ_REMOVE(&sc->sc_txbuf, bf, bf_list);
 	else
 		bf = NULL;
+
 	if (bf == NULL) {
 		DPRINTF(sc, ATH_DEBUG_XMIT, "%s: %s\n", __func__,
 		    TAILQ_FIRST(&sc->sc_txbuf) == NULL ?
 			"out of xmit buffers" : "xmit buffer busy");
+		return NULL;
 	}
+
+	/* Valid bf here; clear some basic fields */
+	bf->bf_next = NULL;	/* XXX just to be sure */
+	bf->bf_last = NULL;	/* XXX again, just to be sure */
+	bf->bf_comp = NULL;	/* XXX again, just to be sure */
+	bzero(&bf->bf_state, sizeof(bf->bf_state));
+
 	return bf;
 }
 
+/*
+ * When retrying a software frame, buffers marked ATH_BUF_BUSY
+ * can't be thrown back on the queue as they could still be
+ * in use by the hardware.
+ *
+ * This duplicates the buffer, or returns NULL.
+ *
+ * The descriptor is also copied but the link pointers and
+ * the DMA segments aren't copied; this frame should thus
+ * be again passed through the descriptor setup/chain routines
+ * so the link is correct.
+ *
+ * The caller must free the buffer using ath_freebuf().
+ *
+ * XXX TODO: this call shouldn't fail as it'll cause packet loss
+ * XXX in the TX pathway when retries are needed.
+ * XXX Figure out how to keep some buffers free, or factor the
+ * XXX number of busy buffers into the xmit path (ath_start())
+ * XXX so we don't over-commit.
+ */
+struct ath_buf *
+ath_buf_clone(struct ath_softc *sc, const struct ath_buf *bf)
+{
+	struct ath_buf *tbf;
+
+	tbf = ath_getbuf(sc);
+	if (tbf == NULL)
+		return NULL;	/* XXX failure? Why? */
+
+	/* Copy basics */
+	tbf->bf_next = NULL;
+	tbf->bf_nseg = bf->bf_nseg;
+	tbf->bf_txflags = bf->bf_txflags;
+	tbf->bf_flags = bf->bf_flags & ~ATH_BUF_BUSY;
+	tbf->bf_status = bf->bf_status;
+	tbf->bf_m = bf->bf_m;
+	tbf->bf_node = bf->bf_node;
+	/* will be setup by the chain/setup function */
+	tbf->bf_lastds = NULL;
+	/* for now, last == self */
+	tbf->bf_last = tbf;
+	tbf->bf_comp = bf->bf_comp;
+
+	/* NOTE: DMA segments will be setup by the setup/chain functions */
+
+	/* The caller has to re-init the descriptor + links */
+
+	/* Copy state */
+	memcpy(&tbf->bf_state, &bf->bf_state, sizeof(bf->bf_state));
+
+	return tbf;
+}
+
 struct ath_buf *
 ath_getbuf(struct ath_softc *sc)
 {

Modified: head/sys/dev/ath/if_ath_misc.h
==============================================================================
--- head/sys/dev/ath/if_ath_misc.h	Tue Nov  8 21:06:36 2011	(r227358)
+++ head/sys/dev/ath/if_ath_misc.h	Tue Nov  8 21:13:05 2011	(r227359)
@@ -52,6 +52,8 @@ extern int ath_tx_findrix(const struct a
 
 extern struct ath_buf * ath_getbuf(struct ath_softc *sc);
 extern struct ath_buf * _ath_getbuf_locked(struct ath_softc *sc);
+extern struct ath_buf * ath_buf_clone(struct ath_softc *sc,
+	    const struct ath_buf *bf);
 
 extern int ath_reset(struct ifnet *, ATH_RESET_TYPE);

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