From: arybchik <arybchik@FreeBSD.org>
Date: Tue, 17 Mar 2015 08:23:15 +0000 (+0000)
Subject: sfxge: prefetch txq->common if TxQ is started only
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=26943bdbf39d9b3b32140814a3868c4e5b2a04f3;p=people%2Fjulieng%2Ffreebsd.git

sfxge: prefetch txq->common if TxQ is started only

Transmit may be called when TxQ is not started yet (i.e. txq->common is
invalid). TxQ state is checked below when mbuf is processed and dropped
if TxQ is not started.

Sponsored by:   Solarflare Communications, Inc.
Approved by:    gnn (mentor)
---

diff --git a/sys/dev/sfxge/sfxge_tx.c b/sys/dev/sfxge/sfxge_tx.c
index 1169ecb0984e..00ffda321a91 100644
--- a/sys/dev/sfxge/sfxge_tx.c
+++ b/sys/dev/sfxge/sfxge_tx.c
@@ -423,8 +423,10 @@ sfxge_tx_qdpl_drain(struct sfxge_txq *txq)
 	stdp = &txq->dpl;
 	pushed = txq->added;
 
-	prefetch_read_many(sc->enp);
-	prefetch_read_many(txq->common);
+	if (__predict_true(txq->init_state == SFXGE_TXQ_STARTED)) {
+		prefetch_read_many(sc->enp);
+		prefetch_read_many(txq->common);
+	}
 
 	mbuf = stdp->std_get;
 	count = stdp->std_get_count;